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HomeMy WebLinkAbout1998-03-16 City Council (42)TO:HONORABLE CITY COUNCIL FROM:CITY MANAGER DEPARTMENT:POLICE TBANSPORTATION DATE:MARCH 16, 1998 CMR:160:98 SUBJECT:RESULTS OF TRAFFIC AND ENGINEERING SURVEYS ON MAJOR ARTERIALS This is an information report and no Council action is required at this time. REPORT IN BRIEF This informational report provides the results of the traffic and engineering surveys that were authorized by the City Council for the purpose of gathering data that would assist in the decision-making process of whether or not to establish radar enforceable speed limits on four residential arterials. Included in the report is information about research that has been done regarding 85th percentile speeds, a comparison of the survey date to 1990 surveys and a summary of other cities efforts to modify current 85th percentile regulations. Staff will return to Council with specific recommendations after the completion of the traffic signal timing stiidy that is currently being completed on the same four medals. CMR:160:98 Page 1 of 10 BACKGROUND In November 1996, staff requested Council approval to complete traffic and engineering surveys for the purpose of gathering information that would assist Council in the decision- making process of whether or not to establish radar enforceable speed limits not to exceed 35 miles per hour (mph) on three selected residential arterial streets. In February 1997,, Council approved the recommendations and also requested that efforts be made to convince. the State legislature to modify existing State legislation regarding the 85th percentile regulation and local government’s ability to use radar for speed enforcement within their jurisdictions. The surveys were conducted on Embarcadero,’ Middlefield, Arastradero and Charleston Roads. This report provides the results and analysis of the surveys, several options for each roadway, and the consultant’s recommendations. Staff is not making any recommendations at this time. A traffic signal timing study is currently being completed on the same streets and staff believes it is important to have the results of this study prior to the development of recommendations. Staff anticipates returning to Council with the results of the traffic signal timing study and recommendations associated with the speed surveys in about three monthsl After receiving Council approval to conduct the traffic and engineering surveys, staff elected to obtain the services of a transportation consultant due to the public interest on the subject and to decrease any perception of bias or subjective conclusions. Staff dislributed Request for Proposals (RFP) to firms with experience in conducting such surveys. Requests were sent to nine companies. Four responses were received. Transportation and Police staff interviewed two of the four companies. Tile fu’m of Fehr and Peers Associates was selected due to their experience, familiarity with the City, and the cost for their services. Fehr and Peers have had extensive experience in performing similar studies in other cities, including Pebble Beach, Mill Valley, and Moraga. They were familiar with vehicular, pedestrian, and bicycle traffic issues within Palo Alto due to the work they had done previously for the School Commute Safety Study. Additionally, Fehr and Peers conducted the Santa Clara County study along Junipero Serra Boulevard through the Stanford University Campus that resulted in the establishment of radar-enforceable speed limits below the 85th percentile speed. The decision to have consultants conduct the surveys and analysis resulted in a delay in the original three-month projection for completion of the work occurred due to the RFP and consultant selection process. After the contract with the consultant was signed, and based ¯ upon the consultant’s suggestion, the actual survey work was not initiated until shortly after the school year began in September 1997. This decision was based upon the premise that CMR: 160:98 Page 2 of 10 it was important to obtain data at the time that increased pedestrian and bicycle traffic was likely to occur. Definitions of Terms Used by Consultant Before providing a summary of the consultant’s methodology, conclusions and recommendations, it is beneficial to clarify and define some terms used in the reports. A~fidymLK~ - The formula used to determine the accident rate is as follows: ( # of accidents x 1 million) / (total vehicle miles of travel) This standard formula used by Caltrans has determined that for typical four-lane urban roadways in the Bay Area, the average accident rate is 3.97 per million-vehicle miles traveled, and for two-lane roadways, the average rate is 1.93. The 10-mph increment of speed containing the largest number of vehicles., 85th Percentile Speed - The .speed at or below which 85 percent of all vehicles traveled during the data collection period. Consultant’s Methodology The California Vehicle Code (CVC) mandates that traffic and engineering surveys include consideration for three factors, including 1) prevailing speeds as determined by traffic engineering measurements; 2) accident records; and 3) traffe and roadside conditions not readily apparent to the driver. Surveys must be conducted in accordance with the Department of Transportation guidelines. Caltrans guidelines allow the setting of speed limits at the first 5 mph increment below the 85th percentile speed. However, the guidelines recommend that the establishment of a speed limit of more than 5 mph below the 85th percentile speed should be done with great care because a disproportionate number of drivers may become violators. Additionally, research conducted by the Institute of Transportation Engineers and the Transportation Research Board (Attachment A) indicates that speed limits should not be set below the median of the 10 mph pace and accident risk is minimized by setting the speed limits close to the 85th percentile speed. The CVC survey requirements include the recording of speeds of 100 vehicles at a location where speeds are representative of the entire section during non-peak times when traffic is free flowing and absent any biasing factors (e.g., poor weather, police presence, accident scene). In order to collect speed survey data, staff asked the consultant to divide the four roadways into different segments and to collect samples of 100 vehicles in each direction. The consultant’s personnel walked and bicycled along certain portions of each roadway to CMR:160:98 Page 3 of 10 ensure that they obtained all information about roadway conditions not readily apparent to motorists. Additionally, the consultant reviewed the two-year history of accidents reported to the Police Department. Summary. of Consultant’s Conclusions and Recommendations The consultant’s detailed analysis reports on each of the four roadways surveyed are attached to this report. A summary of their conclusions and recommendations include the following: Ara~tradero Roa~l Conclusion - Speed survey data determined that the 85th percentile speeds ranged from 34 to 35 mph. The 85th percentile speeds indicate a speed limit of 30mph. The two-year accident history indicated thatthe roadway’s rate of reported accidents is 2.36 which is below the Bay Area average of 3.97. The accident information and non-apparent roadway conditions determined that extenuating issues were not present which would warrant any revision to the 85th percentile findings for decreased speed limits and the use of radar. Recommendation - Based upon all the information obtained, the consultants recommend that the posted speed limit on Arastradero Road between Foothill Expressway and E1 Camino Real be increased from 25 mph to 30 mph. Charleston Road ~ - Speed survey data determined that the 85th percentile speeds ranged from 35 to 36 mph. The 85th percentile speeds indicate a speed limit of 35 mph. The two-year accident history reflected that the rate for one of the three sections (El Camino to Alma Street) was below the Bay Area average accident rate, ~hile the other two sections (Alma Street to Middlefield Road and Middlefield Road to San Antonio Road) were above the Bay Area average rate. Based upon the higher accident rote in the two sections and a review of pace speeds, a speed limit of 30 mph is justified between Middlefield and San Antonio. A speed limit of 30 mph between Alma and Middlefield Road would be below the median of the pace speed and, therefore, not justified. Recommendation - Based upon all the information obtained, the consultants recommend that the posted speed limit be increased from 25 mph to 35 mph between El Camino Real and Middlefield Road and from 25 mph to 30 mph between Middlefield Road to San Antonio Road. Embarcadero Road Conclusion - Survey data reflected that the 85th percentile speeds ranged from 33 to 37 mph. CMR: 160:98 Page 4 of 10 The 85th percentile speeds indicate a speed limit of 30 mph between Alma Street and Walnut Drive and 35 mph between Walnut Drive and St. Francis Drive. The two-year accident history shows that the accident rate for two of three sections of the roadway (Middlefield Road to Walnut and Walnut Drive to St. Francis Drive) were below the Bay Area average accident rate, while the third section from Alma Street to Middlefield Road was higher. While the higher accident rate would tend to suggest maintaining the speed limit at 25 mph, it would be below the median pace speed (29 mph) and would result in over 90 percent of the motorists in violation, and as a result, would not be justified. Recommendation - Based upon all the information obtained, the consultants recommend that the posted speed limit be increased from 25 mph to 30 mph between Alma Street and Walnut Drive and from 25 mph to 35 mph between Walnut Drive and St. Francis Drive. Middlefield Road .C.,oRcdlI~ - The 85th percentile speeds ranged from 32 to 37 mph. The 85th percentile speeds indicate a posted speed limit of 30 mph between the Menlo Park city limits and Loma Verde Avenue and 35 mph between Loma Verde Avenue and San Antonio Road. The accident rate information showed that three of the six road segments (northern city limit to Channing Avenue, Oregon Expressway to Towle Way, and Charleston Road to San Antonio Road) experienced an above-average rate for the two-year period. Because the median pace speed for these sections (28 mph, 29 mph, and 33 mph respectively) was above 25 mph, the indicated speed limit of 30 mph for the first two sections and 35 mph for the last section cannot be lowered by an additional 5 mph if radar is to be used. Recommendation - Based uP-0h all the information obtained, the consultants recommend that the posted speed limits between the Menlo Park city limits and Loma Verde Avenue be increased from 25 mph to 30 mph and from 25 mph to 35 mph between Loma Verde Avenue to San Antonio Road. Current Survey Results Compared to 1990 Survey Results The current speed survey data was compared to data collected in 1990 as shown in the table below. This comparison reflects a general overall reduction in the 85th percentile speeds over the last seven years. This reduction may be attributed in part to increased emphasis on traffic enforcement by the Police Department over the last several years. CMR: 160:98 Page 5 of 10 Strut Se~ents Embarcadero Roll Alma Street to Middlefield Road Middlefield Road to WalnutDrive Walnut Drive to St. Francis Drive Arastradero Road El Camino Real to Foothill Expressway Charleston Road El Camino Real to Alma Street Alma Street to Middlefield Road Middlefield Road to San Antonio Road Middlefield Road Menlo Park City Limits to Embarcadero Road Matadero Creek to East Meadow Avenue East Meadow Avenue to San Antonio Road 85th Percentile Speeds 1990 (85th percentile speed based on sample of vehicles in both directions) 38 41 1997 (85th percentile speed based on sample of vehicles in each direction) 33-35 33-35 35-37 34-35 39 36-36 36-36 35-36 36 32-36 37 33-36 37 36-37 Three-Year Speeding Citation History. The use of radar is the most cost effective and safest method for enforcement of speeding violations on major arterials. As indicated in CMR:468:96, staff has been using radar on these four roadways under study as an educational tool, to assist in decreasing speeds. Attachment A details the number of speeding citations and the number of warnings issued by’ police officers on the four roadways for the last three years. In almost all cases, radar was used to detemfine the speeds of the vehicles for which warnings were given. Staff estimates that radar was used as a tool in about 90 percent of the citations in the school zones and on Embarcadero Road between El Camino Real and Alma Street where radar can legally be used. While warnings often are a useful tool to educate motorists, motorists who routinely use those streets are generally aware that they are currently not in any jeopardy of receiving an actual citation. However, based upon the comparison of speed survey data and the reduction of the 85th percentile speeds, some positive impact has occurred. CMR:160:98 Page 6 of 10 Staff understands the perception that if the posted speed limit of any street is increased in conformance with engineering and traffic surveys that motorists will increase their speed accordingly. However, as referenced previously, past studies and data do not support this perception. The majority of motorists generally travel at the speed which they think is safe and their speed is influenced by factors which include road curvature~ grade, number of lanes, and surface conditions. The research also indicates that setting the speed limits close to the 85th percentile speed minimizes accident rates. Efforts to Change Legislation Staffhas checked with various agencies to determine the possibilitybf convincing the state legislature to modify existing 85th percentile legislation. As noted in CMR:486:96, twb cities, E1 Cajon and Santee, ~were able to get the California Legislature to adopt two exceptions to the speed trap section of the CVC for very specific and unusual circumstances, such as a change in traffic patterns due to major highway construction and a street with a severe curve in the roadway. Both legislative exceptions were adopted for only the period of time during which the circumstances exist. The City of Roseville recently directed its staff to pursue legislative changes that would allow local entities to establish.speed limits lower than the 85th percentile and still permit the use of radar. Roseville’s state senator requested justification information from Caltrans regarding the use of the 85th percentile in setting speed limits. Caltrans’ response clarified that their traffic manual clearly indicates that traffic surveys shall consider the 85th percentile speed and that existing law does not allow the use of radar to enforce speed limits which are established without consideration to the 85th percentile. In May 1997, Roseville requested assistance from the League of California Cities in attempting to get the State to reconsider the 85th percentile regulation. Staff has had several discussions on the issue with representatives of the League of California Cities (LCC). During the last legislative session, Senate Bill 575 was introduced by Senator Knight, which would have allowed local authorities to determine and declare by ordinance any prima facie speed limit for any street, other than a State highway otherwise subject to the 25 mph limit, up to a maximum of 65 mph or for any street other than a State highway where the 65 mph limit is applicable, a speed-limit down to 25 mph without regard to traffic and safety standards or surveys. The LCC opposed this bill due to the belief that Caltrans’ interpretations are based upon reasonable and valid standards. The last action taken on this bill was on February 2, 1998, when it was returned to the Secretary of the Senate. Senate Bill 811 was also introduced last year by Senator Hayden. The purpose of this legislation was to.provide counties with populations of over 750,000 the ability to establish speed limits up to 15 mph less (instead of the current 5 mph) than the 85th percentile and not be considered a speed trap. This bill met with significant opposition by such agencies as the California Highway Patrol, California State Automobile Association and Caltrans. Due to CMR: 160:98 Page 7 of 10 the opposition, the bill has basically died. On February 19, 1998, AB 2222 was introduced by Assemblymember Hertzberg. The impetus behind this bill is to attempt to equalize the use of radar as an enforcement tool to that of the pacing method by eliminating the requirement for speed and traffic surveys every five years. In a conversation with a representative of Assemblymember Hertzberg’s office, due to the strength of the opposition to SB 811 and the fact that experts agree that the 85th percentile regulation is based on valid and reasonable standards, AB 2222 does not attempt to make any changes to that guideline. ALTERNATIVES Staff recommendations will be developed upon completion of the Traffic Signal Timing Study. However, a list of alternatives for each of the roadways is as follows: Arastradero Road b) Maintain the posted speed limit at 25 mph and all speed enforcement would continue to be conducted through the use of the pacing method, except in the school zones where radar can be used when students are traveling to/from school. Increase the posted speed limit to 30 mph so that radar could be used. Charleston Road b) c) Maintain the posted speed limit at 25 mph. All speed enforcement would continue to be conducted through the use of the pacing method, except in school zones where radar can be used when students are traveling to/from school. Maintain the posted speed limit at 25 mph and install signs adjacent to the Stevenson House advising of a senior center so that radar could be used in this section at any ,time. Increase the posted speed limit according to the consultant’s recommendation of 3-5 mph from El Camino Real to Middlefield Road and 30 mph from Middlefield Road to San Antonio Road to allow for the use of radar. Increase the posted speed limit to 30 mph and ~se radar from Middlefield Road to San Antonio. Embarcadero Road a) b) Maintain the postedspeed limit at 25 mph. All speed enforcement would continue to be conducted through the use of the pacing method, except in school zones where radar can be used when students are traveling to/from school. Increase the speed limit to 30 mph from Alma Street to WalnutDrive and 35 mph from Walnut Drive to St. Francis Drive to allow for the use of radar the entire length CMR: 160:98 Page 8 of 10 c) of the roadway. Increase the posted speed limit to 30 mph the entire length and only use radar up to Walnut Drive. Middlefield Road b) c) d) Maintain the posted speed limit at 25 mph. All speed enforcement would continue to be conducted through the use of the pacing method, excep, in school zones where radar can be used when students are traveling to/from school. - -=- Increase the speed limit between the northern city limits to Loma Verde Avenue to 30 mph and between Loma Verde Avenue to San Antonio Road to 35 mph to allow for the use of radar the entire length of the roadway; or Increase the speed limit to 30 mph from the northern city limits to Oregon Expressway (a natural break) and to 35 mph from Oregon Expressway to San Antonio Road, which would allow for the use of radar from Loma Verde Avenue to San Antonio Road. Increase the speed limit to 30 mph the entire length from the northern city limits to San Antonio Road. ATTACHMENTS Attachment A: Attachment B: Attachment C: Three Year Speeding Citation History Speed Zone Guidelines Transportation Research Record Arastradero Road Speed Survey Report Charleston Road Speed Survey Report Embarcadero Road Speed Survey Report Middlefield Road Speed Survey Report PREPARED ~Y:Ashok Aggarwal, Acting Chief Transportation Official Lynne Johnson, Assistant Police Chief DEPARTMENT HEAD: KENNETH R. SCHREIBER Director of Planning and Community Environment CMR:160:98 Page 9 of 10 DURKIN Police Chief CITY MANAGER APPROVAL: CMR: 160:98 Page 10 of 10 ATTACHMENT A THREE YEAR HISTORY OF SPEEDING CITA~ONS/WARNINGS ON FOUR ARTERIALS 1995 1996 1997 Cites/Warnings Total Cites/Warnings Total Cites/Warnings Total Arastrad~ro Road 76 / 6 - 82 33 / 33 - 66 124 / 230 - 354 Middlefield Road 91 / 21 - 112 115 / 240 -355 139 / 392 - 531 Charleston Road 37 / 3 - 40 78 / 77 - 155 89 / 115 - 204 Embarcadero Road 211 / 121 - 322 270 / 521 - 791 322 / 539 - 861 -Speed Zone Guidelines A Proposed Recommended Practice Institute Of Transportation Engineers 525 School St., S.W., Suite 410 Washington, D.C. 20024-2797 Standard ITE Metric Conversions Durin~ Ihc .service life ~,1 ~l~i., d,,,.’umcnu use of the melric ~yslcm in the United States is expected ~o uxpand. The lbllm~ m,g c~,mm,,n ~c~,,r, repre~em lhe appropriate magnitude of conversidn. The quantities ~iven id U.S. cuslomao unn, ~n fl~e ~ext. ulbles or l’i~ures, represem a precision level lha~. in practice. Dpically doe~ not exceed ~,~, ,~uilicunl figures. In makin~ conversions, il is important to nol falsely imply a ~rea~er aceurac) in the pr,,du~’~ ~han exisled in lhe original dimension or quamity. Howcver. certain appli~ation~ such u~ ~ur~e)iu~ ~Iruature~. curve ol’fsel cal~ulation~, etc. may require ~reat pre~ision. Conversions lb~ sucl~ purpo~c, are given in parenthcses. Volume Icuhicinch =It, era3 i1e,.39) I cubic fool =1L1)28 I1~3 ,ll.()2N3l} I cubic ~a)’d =~).~m3 ,~)-~-151 I qthii’l =,),M I ,li:~r-- I galhm =; , I. ~ -.’,5, Speed milc,,/huur J’l,’lll pe ra I tl re I(, c~,n’,,:rt -. I: I I:al+ucuh,,’i~ ~,, i ,’!,:’u,~. ~llbll’aCl 32. Iher| di’. Me I’.v 1.8. --_.!) N-I !11- =I).-I hu ~he~’t,u’e,i -- ass pl)und =))))~ k.,._’ ~kfl~,gram,,--(1.02~) =+) I.~ k,_’ ~ki!ogram,i --_..)fill1 k’.’ Iull-’ 1 .ilaht =II h|\ (lumen,, per|||- -- ILLS) =~ I ,’d/m- |,’;Uldela~ p~’r In2 -->.4_61 l:,)l" other unit’, )’vl’cr h’)lhc :\:u,’)~, .m .X,)cict.~ ul"l’csli,g Malcrial,, (1910 Race Streel. l’hiladelphia. I)A o This report was approved as a ~oposed Recommended Practice of the Institute of Transportation EnEineers to solicit comments in September 1993. Comments are being sought on this report to assist in the consideration for adoption as a Recommended Practice of the Institute. Comments. questions, and any requests for a public hearing should be submitted tO the Director of Technical Programs at ITE Headquarters by February 1, 1994. Any comments and suggested revisions received will be considered and addressed by the committee before forwarding the report to the ITE Standards Approval Board for a final decision on adoption as a Recommended Practice of the Institute. The Technical Council Committee 4M-25 was responsible for the development of this Proposed Recommended Practice. Committee 4M-25 was chaired by William C. Taylor, P.E. (M), Professor, Michigan State University. The other committee members were: John P. Bradley, P.E. (M); David S. Johnson, P.E. (F); Rodney L. Long, P.E. 0VI); Patrick T. McCoy 0VI); Prahlad D. Pant 0vf); Martin R. Parker, P.E. (M); Salem Spitz, P.E. (I); James J. Stanek, P.E. (A); Gary P. Foxen (M’); Bruce B. Harry, P.E. (M); John P. Hoffstatter, P.E. (F); Cynthia L. Hoyle, AICP (A); Richard H. Kanak, P.E. (A); Robert L. Meyer, P.E. (F); Massoum Moussavi, P.E.; Guy P. Olsen, P.E. 0VI); Matthew E. Thompson, P.E. (’M); and Gerald L. Ullman, P.E. 0VI). Members of the Department 4 Standing Committee at the time the report w.as approved were: Kay Fitzpatrick, P.E. 0Vi) (Chair); Jeffrey F. Pardati, P.E. (A) (Asst. Chair); Brian E. Hicks, P.Eng. 0VI); William C. Kloos, P.E. (’M); Charles P. Kole, P.E. (FL); Edward J. Seymour, P.E. (A); David E. Woosley. P.E. (’F); and Donna C. Nelson (A). Eugene M. Wilson, P.E. (I:) was the Chairperson of TechRical Council and Brian S. Bochner. P.E. (F) was the Assistant Chairperson. Certain individual volunteer members of the Institute Recommended Practices developing bodies are em- ployed by Federal agencies, other governmental offices, private enterprise, or other organizations. Their participation in these activities does not constitute endorsement by any government agency or other organization of any of the Institute Recommended Practices developing bodies or any Institute reports which are developed by such bodies. The Institute of Transportation Engineers (ITE) is a professional society of more than 13,000 transportation engineers and planners, who are responsible for the safe and efficient movement of people and goods on streets, highways’ and transit systern.~. 1TE members are engaged in planning,’ designing, operating." managing, and maintaining surface transportation systems in 70 countries. Since 1930 the Institute has been providing transportation professionals with programs and resources to help them meet those responsibili- ties. Institute programs and resources include professional development seminars, technical reports, a month~" journal, local, regional, and international meetings, and other forums for the exchange of opinion. ideas, techniques, and research. Institute of Transportation Engineers 525 School St., S.W. Suite 410 Washington, DC 20024-2797 USA Telephone: (202) 554-8050 FAX: (202) 863-5486 © 1993 by the Institute of Transportation Engineers. All fights reserved. ITE Publication No. ILP-024 200/GP/196 Thh’d Printing 1.Introduction The purpose of speed zoning as stated in the Uniform Vehicle Code is to establish a speed limit that is "reasonable and safe for a given section of roadway." There are at least two difficulties when interpreting this statement. The first is a question of "reasonable to whom?" and the second is the implication that there is truly a cause and effect relationship between speed limits and safety. It is clear from the controversy surrounding the use of speed zones that there are differences of opirdon as to what is a reasonable speed among drivers, residents, legislators and enforcement officers. Thus, compl~ance with the vehicle code in determining the appropriate speed limit to post in a speed zone requires a definition of the term "reasonable speed." The use of speed zones to increase safety depends on the assumption that a direct relationship exists between a change in the speed limit and a change in driver behavior that r~sults in increased safety. Figures 1 and 2 show that changing speed limits alone seldom changes speed characteristics of the traffic stream, which indicates that this assumption may be invalid. In fact, the current practice of decreasing the speed limit results in a higher percentage of drivers in violation of the speed limit, while ¯ their speeds have not changed. It is improbable that this results in increased safety. This practice might only serve as an ineffective substitute for other traffic engineering measures that could result in increased safety. However, speed zoning as a traffic engineering tool should not be ignored. It is widely used, and many states, counties and cities have developed policies and guidefines for the implementation 65 60 ~ 55 Eo "°" I ! 35 40 4530.50 55 60 65 85th % Speed Before, rni/n Figure 1. Prevailing speeds before and after lowering speed limits Soothe: Spee~l Zoning in Anteric~ Some Pre~ Research Re~u~. FHWA, 1~. 55 25 !!T , 25 45 55 65 75 85th % Speed Before, mi/n Figure 2. Prevailing speeds before and after ralsing speed limits Source: $~eed ZonL~g in Amevlc.a: Some Pre~ Xe~ea~ Re~ulU. F’ffWA, 1989. Speed Zone Guidelines - A Proposed Recommended P~ctice 1 of speed zones. Speed zoning, when properly applied and enforced, can conwibute to highway safety. 2. Inconsistencies in Speed Zoning In a survey conducted by this committee, the two most frequently cited reasons for establishing speed zones included increasing safety and informing the motorists of the re~onable speed for a particular segment of the road. However, there are serious inconsistencies in the practice of speed zoning that make it difficult to justify speed zoning as either a safety measure or a means of communicating the reasonable speed to the motorist. These inconsistencies are described as follows: Location of speed zones. Even though traffic engineers and the public both perceive speed zoning to be a safety tool, such zones frequently are established primarily in response to citizen demands rather than where an accident or accident potential problem exists. It is not surprising, then. that studies of accident reductions .resulting from speed zoning are inconclusive. If speed zones are to be an effective safety device, the profession needs consistent guidelines, based on an engineering analysis, to determine where and when to establish these zones. Speed limits. Most traffic engineers support the use of the 85th percentile speed as a basis for determining the appropriate speed limit. However, as shown in Figure 3, the majority of posted speed limits in speed zones nationwide are much lower than the 85th percentile speed and in many cases lower than the average speed. The ¯ 5O 3O 25 2O 25 30 35 4O 45 Pored Speed. Limit 5O --e--. Average 85th %tile --,,-.- Average Mean Speed Figure 3. Prevax3ing speeds in m-ban areas Soothe: $t*eed Zoning in limits are of-ten set to reflect either legi.slatively created limits or simply to accommodate the demands of the public. The profession also needs to be consistent in applying guidelines for posting speed limits in speed zones. Uniformity in the application of traffic control devices is one of the goals of the traffic engineering profession. Enforcement tolerance. This final inconsistency refers to the practice of enforcing the speed limit in speed zones. Where speed limits are artificially low, the enforcetuent tolerance must be high. Since enforcement action against a large proportion of a traffic stream is not possible, the enforcement tolerance must be increased when the speed limit is set below the 85th percentile speed. While a large tolerance may be necessary for zones where the speed limit is artificially low, it is not appropriate to use this same tolerance where the speed limit is set at or near the 85th percentile speed. Since all_speed zones have identical signing, motorists cannot distinguish between the two types of speed zones¯ 3. Rationale for Consistent Speed Zone ¯ Guidelines As illustrated in IEigures 4 and 5, several studies have demonstrated that drivers who travel faster than the 85th percentile speed of the traffic stream have a higher accident involvement rate than those drivers whose speed is close to the 85th percentile speed. Posting the speed limit at the 85th percentile speed informs the motorist of the maximum speed consistent with a low risk of an accident. Thus, the overriding basis (from a safety perspective) for speed zoning should be that the creation of the zone, and the speed limit posted, reflects the 1 2 Institute of Transportation Engineers maximum sp~e.d considered to be safe and reasonable (that is, the 85th percentile speed). A second rationale for consistency in speed zoning practice is the desire for equitable treatment of motorists. When speed linfits are set artificially low and enforcement action cannot be directed at all the violators, the enforcement officer has too much discretion in selecting the motorists to be penalized. The cost of being selected can include both a fine and an increase in the cost of insurance. This type of enforcement ultimately leads to poor public relations for both the traffic engineering agency and the enforcement agency. A third rationale is the need for consistency between the speed limit and other traffic control devices. Signal timing and sight distance requ~ements, for example, should be based on the prevailing speed of traffic. If these values are based on a speed limit that does not reflect the prevailing speed of traffic, safety, might be compromised. If speed zones are to fulfill their intended function as a traffic conu’ol device used to enhance highway safety and operations, these inconsistencies must be eliminated. As currently practiced, speed zoning violates one of the basic traffic- engineering premises stated in the Manunl on Uniform Traffic Control Devices: "Uniformity means treating similar situations in the same way. The use of a standard device does not, in itself, constitute uniformity. A standard device used where it is not appropriate is as objectionable as a nonstandard device." The most desirable method of eliminating these inconsistencies would be to require nil speed zones to be based on an engineering study and to enforce all speed limits with equal rigor. Unfortunately, traffic engineers, enforcement agencies and the courts seem to be moving in 10 TWO-LANE MLR.TILAN~ AU. ROADS 1 l S-15 15..30 ~0-5~ 50-70 7~,~ 8.%95 SPEED I~RC.,ENTII~S Figure 4. Accident involvement ratio versus speed percentile (multiple vehicle accident involvement). Source: A~scs:ment of Current Speed Zon,~ng CH~ria. Analysis Groups Inc., J~nua~ 1989. the opposite dixecfion, with more - - speed zones being established based on other criteria, more speed limits being set incorrectly, and ~eater tolerance in th~--~nforcement of ¯ these speed limits. 4.Recommended Practice The following recommended practice will provide a consistent basis for the application of engineering principles to speed zoning. It is recommended that speed zones only be established on the basis of an engineering study. Each speed zone should b~ periodically restudied to, determine that the established speed lirnk is appropriate.. The suggested maximum interval between studies is five years. In addition, an engineering study should be conducted whenever there is a change in the roadway that would affect the prevailing speed. Such changes would include elimination of parking, added lanes, signal coordination, changes in roadside development, and so forth. It is recommended that the engineering study include an analysis of the current speed distribution of free-flowing vehicles. It is further Speed Zone Guidelines - A Proposed Recommended Practice 3 ’ ---, TWO-LANE --~ MULTILANE .... ~ ALL ROADS SPEED PERCENTILES Figure 5. Accident involvement ratio yersus speed percentile (single vehicle accident involvement). Soo, r~: Assess~nent of Cu,’rrnt Speed Zoning Criteria. Anal~-is Groups In~ .Imaua~ 1989. recommended that the speed limit within a speed zone be set at the nearest 5 mph increment to the 85th percentile speed or the upper limit of the 10 mph pace. No speed zone should be established in a location where the 85th percentile speed is within + 3 mph of the statutory speed limit. The existing speed limit within a speed zone should not be changed if the 85th percentile speed is within + 3 mph of the posted speed limit. The engineering study may include other factors such as: a. Geometric features including vertical and horizontal aligTmaenL and sight distance b. Roadside development c. Road and shoulder surface characteristics d. Pedestrian and bicycle activity e. Speed limits on adjoining highway segrnent.s f. Accident experience or potential However, in no case should the speed limit be set below the median speed of the 10 mph pace. Speed zones should not be used to warn motorists of hazardous conditions. If a hazardous condition exists within the road segment under study, this condition should be corrected or an appropriate warning sign in conjunction with an advisory speed plate shotdd be posted. ¯Enforcement of speed limits within speed zones should be uniform. Efforts should be made to coordinate the implementation of speed zones and the enforcement policies __with the governing etLforcement agency. It is recommended that each governmental agency adopt a uniform policy for enforcing speed limits established within speed.zones. 5.Legal Issues In addition to the application of this recommended practice, some changes in laws or ordinances would be required to eliminate inconsistencies in stieed zoning. This would include the codification of the requirement for engineering study justification of speed zones as well as a requirement for periodic restudy. It should also include some distinction in terms of enforcement among various speed zones. For example, on roadways where the recommended practice is not followed, enforcement should only be based on violation of the Basic Speed Law. 6.Definitions As used in this documen.t, the following terms are deemed as: 85th percentile speed - the speed at or below which 85 percent of the sample of free-flowing vehicles are traveling. This speed should be determined by conducting a spot speed study following the procedure contained in the ITE Traffic Engineering Handbook. Institute of Transportation Engineers ¯Advisory speed - the speed at which a specific feature along the street or highway can be safely traversed. ¯Basic Speed Law - no person shall operate a motor vehicle at a speed greater than is reasonable and proper for the prevailing conditions. *Pace - the 10 mph band of travel speeds cbntaining the largest number of observed vehicles. ¯Speed limit - the maximum (or minimum) speed permitted on a section of street or highway. This limit might be statutory or it might be established within a speed zone on the basis of an engineering study. ¯Speed zone - a section of street or.highway where a speed limit different from the statutory speed limit has been established. ¯Tolerance -the numerical difference between the speed limit and the minimum speed at which enforcement action is taken. Bibliography *Analysis Group Inc., Assessment of Current Speed Zoning Criteria. January 1989. U.S. Department of Transportation, Federal Highway Administration, Speed Zoning in America: Some Preliminary Res~-~rc~t-Results. Washington, DC, November 1989. U.S. Department of Transportation, Federal Highway Administration, Synthesis of Speed Zoning Practices. Washin~ota, DC, July 1985. Speed Zone Guidelines - A Proposed Recommended Practice TRANSPORTATION RESEARCH RECOR D No. 1281 Safety and Human Pe,formance Human Factors and Safety Research Related to Highway Design and Operation 1990 A peer-reviewed Imhlicalion of the Transportation Research Board TRANSPORTATION RESEARCH BOARD NATIONAL RESEARCH COUNCIL WASHINGTON, D.C. 1990 ’1"11,4 N5 I’O1! TA TI I)N R ES IL4 R ( "11 ’R E( ! ~ R I) I .’-,~ I Assessment of Current Speed Zoning Criteria DAVID L. HARKEY, H. DOUGLAS ROBERTSON, AND SCO’Vr E. DAVIS As early as 19,17, studies ¢onc|udcd that the majorily of drivers ignore speed limils m~d drive at speeds that they believe are safe and reasonable. Since then, some studies have SUPlmrted this conclusion whereas olhers indicnlcd thal speed limits dt~ affect travel speeds in varying degrees, hi an FI IWA-spo.sored assess- merit of current speed zoning criteria, speed a~d accident data were collected at 50 locations, both urban a~tl rural, in four states on rond~vays with pnslctl speed limits rangitlg from 25 to 55 mph, These data we~c mmlyzcd to determine travel N~ecd characler- islics, compliance with Imstcd ~pccd limits, and the point of min- imum accident risk. Significant findings were as follows: Mean speeds exceeded posted speed limits by 1 to 8 mph; 85th- percentile speeds raugcd from 6 to 1,1 mph over the posted speed limit, or 4"to 7 mph over Ihe mean ~pcctl; the majority (70.2 percen0 of free-flow drivers obse~cd did not comply with posted speed limits; in gcucral, 85 percent complim~ce was achieved at speeds 10 mph over the ImStCd speed limit; accident rates for the 25-mph zones were consistc~tly much higher than for any of the other zones; and the speed al which accident risk was minimized occurred at the 9[)th percentile of the travel spccds observed, The practice of establishing speed limits, or speeq zoning, bcgan carly in the history of motorized travel when og~dals realized that excessive speed cohld result in damage and injury to others. The first spcctl limit in Ihc United States was enacted in Commc6cut in 19111 and since that time the evolution of speed limits in this country has bcc~m~c both complex aud ctmtrovcrsiat. As early us 1947, s~udic~ have concluded that the majority of tlrivcrs igaorc speed limits and drive at speeds tha( arc bclicvctl safe and reasonable (I), Since then, some studies have SUplmrtcd this conclusion whereas other res~mrch indicated speed limits do affect travel spcetls in varying degrees (2). Perhaps one reason for the lack of consensus on the effect of speed limits is the lack of trot’fortuity in establishing spee0 limits, Spccd zo.ing is generally dcfinctl as the establishment of safe and reasonable ~pccd limits. Although safe speed is difficult to define, rcnsonablc spccd is nearly impossible for nil drivers to agree on. Broad intcq~rctalion5 of these terms combined with the lack of sound cugiucering knowledge has led to use of a wide wtricty of rcgulatkms and procedures posting speed limits. Lack of uniformity in speed zoning among jurisdictions creates problems h)r motorists, law enl’ot cc~Kaent officials, and judges. If posted speed limits are unreasonably low, the majority of drivers become technical violators of the law, which places law enforcement officials and judges i. the position of ltrbi- I). I.. I hukcy aml S. E. I.I.’wis, The Scicntcx (’rap.. 5011 Eaxt head Street, Suite 315, Chatlotlc, N.C. 282112. II. I). I/,obcrt.~tm. U,ivcr.~ity nf Nollh Carolin:h Department or Civil Engineering, Charlotlc, N.C. 211223. lra~ily selecting violators, This process also produces tCriticism of highway officials responsible for posti.g speed limits can often lead to concerned citizens and legislators taking active rule it~ speed zoning decisions (3). In an FI IWA-sponsored assessment of current speed zm~ing criteria, speed and accident data were collected at 50 tions, both urban and rural, in four states ou roadways with imstcd speed limits ranging from 25 1o 55 mph (4). These compliance with posted speed limits, and Ihc point of minimum accident risk, SI’I’E SI~LECTION Although travel speed characteristics may vary [rum tree to another, an attempt was illade to select states believed be representative of travel speeds in a p;ulicuh~r rcgitm nl Ihc country. This result was accomplished by dividing the into four geographic regions (southwest, northeast, midwest. and west) hnd selecting two states Trom each rcgitm primm’y and one alternate) on the basis of Ihc [ollmving critc~ ¯ Tim national maximum speed limit (NMSI.) data ,base had to contain 3 years of vehicle speed data for the ctmtxol sampling locations; ¯ The accident d;lla b;ise had 1o be COllll~UlCl’izcd alld llcccs- sible by highway location; and ¯ The accident data reported by ench slille had to ctmtain. at a minimum, estimated travel speed, posted speed limit. violations cited, time of day. day of week, severity, lypc ~1 collision, and number of vehicles im, olvcd. On the basis of these criteria, the four states selqcted were North Carolina. Delaware~ Colorado, und Ariz~ma, Selection of r6atlway scgmcms within each sIillc Ior which speed and accident data were collected began with the slrm- ification of sites by area type. roadway type. and speed limit. On the basis of national daily vehicle miles of travel (DVM’I’) obtained from the l lighway Performance Mouitt~riug System {ILl’MS) data. sites were sclcctctl in I1 cells ~8 urban and 3 ~ural cells) as prcscntctl in Table 1, The II cells clmscn wc~c multilmlc and two-lane cells with the largest DVMT value. laclutlcd were five multihme sites and six two-htnc silos in Sites were sclcclctl in each of the ftmr stales using n data tape cuntaining I lPMS roadway segments at~d their clm~ac- teristics. Scgme.ts were first stralilicd into Ihc I I ccll~ itlcn- Iilictl for data collcctiotl in "l’ahlc L. A list uf scgllwnts )vithin i :2 haractcristics collected \vcrc Development type (commercial, residential, etc.). Number of intcrsocdons (signalized and unsignalized), Number of imcrsccdn~ I lurizontal curvature (llOIlg, moderate, severe),. "l’crrain (flat, rolling, mountainous), Mcdiall typ~ and width, l)ostcd speed limih ~dvisory speeds and speed zones, Lane width, and Shoulder type and width. ~ach item was collected for the cmirc length of each segment. :or purposes of collecting {hose data and the acciden~ data, ’ach segment was cxlcndctl in both directions bcyo~d the )riginal mileposts defining the HPMS section as long as the "haraderistics of the site remained’constanL Amuml avm age daily traffic (AADT) volume for each road- vay segment was obtained from the state. This information yes used in combi~mdon with the accitlcnl dale to develop ~ccident rates. kccident Data l’hrce years of accident data were collected from [l}c slates or each of’tile roadway segments-whc~q speed data were :ollcctcd. Variables obtained were ¯Rot, re, ¯Milepost, ¯Date, ¯"Fim6of day, ¯Day of week, ¯Number of/.juries, ¯Number of fatalities. ¯Speed involved (yes or no), " ¯Collision lype, ¯Vehicle lype, ¯Estimated travel speed, ¯Weather conditions, ¯Surface conditions, ¯Driver condition, ¯Accident severity, m~d ¯Intersection accident (yes or no). Of the variables listed, estimated travel speed was tile only one not obtained in all states. Although the value was re- corded on the accident report in the field by the investigating officer, data were not available from the compttterized accident file in Arizona or Delaware. 1,1ES U L’I’S Travel Speed Characteristics Getwral Rural, small urban. ;rod urban stratification used in identifying sites from the I IPMS data base was eliminated oIl the basis TIeANSI’OR’I’A TION RESEAI¢CI! I,:E(’Oltl) 1281 of observalions of Ihe field thrill collcclion team. Some ttrbatl sites al~pearcd to be more rural than urban and vice-versa on the basis of factors such as vehicle volumes, development lype, iutcrseclion and driveway density, etc. Thus. giving results of the analysis in terms of rural versus urban would have been- not only difficult, but misleading. Therefore, results are given in terms of posted gl)ced limit and road type (n~,ll~cr of lanes). Geometric and site atH ibutcs collected i~hc~icld ID’file project team were {hen used to belier dcline arc;~ lypc influences on travel speed. Distribution of the 50 sites (by Ilumber of travel hines and posted speed limit) used in the analysis are presented in Table 2. Figure 1 shows the box plots of travel speed percentiles for each speed zone. Travel speed percentiles usdd for each plot arc 5, 15, 50.85, and 95. Plots express the normality of each speed zone data set because the 5th, 15th, 85th, lll~tl 95th percentiles arc symmetrical about the 5(}th percentile. As shown by these plots, v~riations across speed zones are similar, indi- - caring a htm~ogencous sample. TAB LI’~ 2 srI’ES BY NUMBER OF "rI~,AVEI. LANES AND POSTED SPEED LIMrr Road Type Two- Lane Hulti- lane DISTIUBUTION OF STUDY Speed Limit (mph) 25 30 35 40 45 50 5~ 4 3 6 3 5 4 4 --~i1 5 2 6 4 2 uJ J gO 7O 5O 3O 10 I I’, I I ,,,i,1 50.~5. 40 45.50.55 POSTED ,SFEED LIMT I:I(;UI{I:. 1 Itox plots of speed pcl’C~:,~lil~:s I’or t, at’h speed zoitc, II, TRAN3PORTA TION ItKSEAI~CII I¢I’:CORD zones (see Table 5). For both cars and trucks, 85th-percentile speeds were 4 to "7 mph greater than the mean speed. The largest differcnce bctwc.cn car and truck speeds for an indi- vidual site was 9.8 mph, whereas the smallest observ.ed difference was zero. , Day Versus Night Free-flow mean and 85th-perccntile speeds presented in Ta- ble 6 for daytime, nighttime, and dawn and dusk indicated a 0- to 3-mph difference. However, no consistent increase or decrease in speeds was observed on the basis of time of day across all specd classes. The largest observed difference for an individual site wits a night speed of 12.5 mph below the dawn and dusk speed. Several sites had speed differences less than 0.5 mph. Compliance with Posted Speed Limits General Throughout theanalysis, conq)li:mcc was treated in lerms of the pcrccatagc of flcc-flow vehicles exceeding the posted speed limit, i.e., those vehicles not in coml)liance with the law. In general, data from the 50 sites revealed that the majority of drivers (70.2 percent) did not comply ~vith posted speed limits. Noncompliance by sitc ranged from a low of 32 percent to a high of 97 pcrccnrwith the exception of one site where non- compliance was only 1 percent. This finding remained gen- crally consistent throughout the analysis, regardless of the factors or combination of factors examined. Figure 4 sho~vs pcrccm noncompliance by posted speed limit. The numbcr at the top of each bar is the percent exceed- NONCOMPLIANCE (%) 83 7471 63 63 ~5 30 35 40 45 50 55 ,5 ,I0 ~15 POSTED SPEED LIMIT (mph) FI(;URI~ 4 limit. Percentage of noncoml)li:mce I)y posted speed ing the limit; the nc×t nut~lbcr is the percent exceeding the speed limit by more than 5 mph; the next by mr)re than 10 mph; and the bottom number by more than 15 mph. Overall, the pcrccnt of drivers exceeding posted spccd limits by more than 5 ml)h wits 4(I.8 i)crccnt; by more than 1(I ml)h, 16.8 pcrccnt; and by more than 15 mph, 5.4 percent. If the 85tb- TABLE5 (’AI~ANI)’rltUCKSI’EED CIIARACIIH~IS’IICS Speed Mean Speeds(mph)85th %tile S~eeds (mph) Limit (mph)Car Truck 25 30 35 40 45 50 55 Car Truck 31.1 29.0 36.6 32.6 38.6 36.6 41.8 38.4 48.6 44.4 51.6 48.1 56.3 53.9 36.2 42.2 44.6 48.4 54.6 58.6 62.3 33.6 39.1 41.3 44.9 51.1 54.5 60.5 TABLE 6 FREE-FLOW MEAN AND 85th.PEI~,CEN’rILE SPEEDS FOR DAYTIME. NtGlrl’l’llvlE, ^NI) DAWN O1~, DUSK CONDrrlONS Speed Limit (mph) 25 30 35 40 45 50 55 Mean Speeds (mph) Day Night 30.8 30.8 36.6 34.4 38.5 38.9 41.4 39.8 48.5 49.3 51.3 51.6 56.1I 56.g Dawn/Dusk 3i.1 36.7 38.6 41.2 48.7 51.8 56.2 85th %tile Speeds (mph) Day Night 36.1 35.7 42.1 39.2 44.4 44.9 48.1 45.9 54.4 55.0 58.1 56.9 62.2 61.9 Dawn/Dusk 35.9 41.9 44.4 48.2 54.8 58.2 61.8 48 / 77ANSPORTA170N RESEARCII RECORD 1281 q’AIIloI~ II ACCIDENT RATES USING \VEIGIrrED IH:GRESSI(,~NS Type of Accident Rate Overall Injury Fatal Daytime Nighttime Speeding Number of Driveways per Mile <2O 1.46 0.64 0.00 0.91 0.27 0.46 20 or more 3 .ii* -I-. 4 6* 0.03 2.47* 0.64* 0.91 * Indicates significant difference from the <20 group at the 95 percent confidence level. 1ooooo -40 -20 0 20 40 o FP~E’WAY yAP~ATFON FR(~ NF_AN $~ED (~/h) FIGURE 7 Accidc.t i.voh’e,ltent and d,:viatimt from mean speed o1" traffic stream for rural high.’ays n.d freeways (5,6L Colorado. Variation from the mean speed was plotted against involvement rate, which, was defined as weekday, nonalcohol, and noninterscction involvements per 100,000 veh-mi (see Table 12 and Figure 8). The lowest involvement rate for this curve occurred at 7 mph above a mcan spccd of 44.2 mph at 24 involvements per 100,000 vch-mi. A closeup of this low point is show,~ in Figure 9. A proportion of the ct, mulative speed distribt, ti~m curve for North Caroliml and Colorado " data, with respect to the variation from the mean speed~ is also shown in Figure 9. On the basis of these data, the speed at which the accide.( risk was minimized occurred at the 90th pc.rce,~tile of the travel speeds observed, as shown in Figure 9 by the dashed line that projects upward from the low point of the accident involvement rate curve to the intersection of the cumt, lativc Sl}cetl distribution ct, rve and then horizontally to the right-hand scale. ASSESSMF~NT OF CRITERIA Criteria uscd to cstablish speed limits arc i,upo,’t:mt as It) whether speed limits are deemed reasonable by the public and whether accident risk is truly minimized. Of the 44 non- 55-mph sites used in this study, 21 had speed limits set on the basis of c.ginecring studies, often with 85th-pcrccntilc speed as the governing factor. Of the remaining ~itcs, 10 were stat- utory limits, 2 were based solely on engineering judgment, and the criteria by which 11 were set were unknown. In Table 13, the percentage of vehicles exceeding the" speed limit is shown ft)r each speed limit class by the criteria used to estab- lish thc limit. In no case is compliance good. but it is cxtrcmcly poor for the lower-speed zones in which statutory limits arc imposed or in which engineering judgment by itself was used in setting the speed limit., Examining die distribution of percent noncompliance, a natural breakpoint was found at 60 percent. A total of 12 sites exhibited n noncompliance rate of 60 percent ~r less prcscmcd i. Table 14. Also listed arc the accidcnl rates for each of those segments. The average accitlcni rate for the non-55-mph sites was 4.27 accidents per million veh-mi Of the 12 sites with low COml~liance, 7 exhibited an accidcnt rntc h)wcr than the average; of Ihosc 7, 3 had spuctls csl~d~- lishcd ot~ the basis of an engineering study. 3 had statutory limits, and 1 was unknown. The speed statistics reveal that only 7 of the 44 sites had mean spcctls lower than the posted speed limits, and no site had an 85th-I~crcentile speed less than the posted limit. SUMMARY OF FINDINGS Analysis of travel speed, compliance, and accident risk produced the following significant findings: - klcat~ Sl)ectls cxccctlutl the posted spcetl limit by I ml)h; ¯ 85th-pcrcentile speeds ranged from 6 to 14 mph over the posted speed limit or 4 to 7 mph over the mean speed; ¯Cars travel 1 to 5 mph faster than trucks for all speed ZOI1CS; ¯No cu.sislcm increase or dccr~s~ limc (}~ day was ob~crvcd across all ~pc~d cla~c~: ¯"rhc majorily (70.2 pcrccnl) did .{~ c~)mply wilh po~lcd Sl)c~d iimil~: IOO0 100 INVOLVEMENT RATE (per 100,0OO veh-mi) 10 "- -7.5 -5 IRVOLV[II[R i" ILATIVE II II Lowes Occur (appr PERCENTILES (%) 95 Point a t the ximatel -2.5 0 2.5 5 7.5 10 12.5 VARIATION FROM MEAN SPEED (mph) =90 ~85 / 18075 n the we 9Oth%,e 7 mph ter meal 0 15 17.5 []NOIq-55 mph HWYS ~ PERCENTILES FIGURE 9 Low-point accidenI involvement rate and cmuulalive speed distril)ulio, curves for Nor|h Carolina and Colorado. -~--- TAI}IoE 13 I’ERCENTOFVEIIICLESEXCEEDINGSPEED LIMIT FOR EACII SPEED LIMIT CI~,rrEI~,ION Criteria Speed Engineering Engineering Statutory Unknown Limit Study Judgement 25 74.0 30 77.5 35 63.9 40 60.1 45 76.7 50 74.0 96.0 76.0 95.0 90.2 54.9 73.0 53.5 87.0 52.0 52.5 64.1 67.4 "FABLE 14 STUDY SITES WITII NONCOMI’LIANCE RATES OF 60 I’ERCENT OR LESS Site No.Noncompliance (%)Accident Rate (Acc/MVM) 340 2965 361 217 8170 214 133 304 436 041 O43 120 51.0 52.0 32.0 54.9 58.2 41.6 58.0 41.0 58.0 52.0 58.0 57.0 0.79 1.37 3.2Q’ 0.39 1.71 5.77 1.47 0.42 8.76 19.14 8.31 8.60 ATTACHlqENT C- Final Report:- ARASTRADERO ROAD SPEED ZONE ANALYSIS Prepared for: City of Palo Alto Prepared by: ~Fehr & Peers Assodates, In~ Transportation Consultants December 1997 971-1095 ..... II. III. TABLE OF CONTENTS EXECUTIVE SUMMARY ...........................................1 Summary of Results -1 Recommendations ’1 GENERAL INFORMATION .........................................5 ENGINEERING & TRAFFIC SURVEYS ...............................7 Prevailing Speeds ...................................................7 Roadway Conditions ...............: ................................8 Accident History ...................................................9 Recommendation ..................................................10 1 Arastradero Road Corridor ...........................................2 Table~ Roadway Conditions and Accident Rate Information "3 Recommended Speed Limit ...........................................4 ---Prevailing Speed Data ...............................................7__~. Two-Year Average Accident Rates .....................................9 Appendix Appendix A - Radar Speed Data Engineering and Traj~fic Survey Report for Arastradero Road between El Camino Real and Foothill Expressway December 1997 ¯ EXECUTIVE SUMMARY Fehr & Peers Associates, Inc. was retained by the City of Palo Alto to conduct a speed zone analysis for a 1-mile section of Arastradero Road. The intent of this study was to conduct an_ engineering and traffic survey consistent with the California Vehicle Code (CVC) and CalTrans guidelines for consideration by the City Council to post speed limits which could be enforced by using radar. The section of Arastradero Road from Foothill Expressway to E1 Camino Real was considered one section for this speed survey. Th~ study corridor is illustrated in Figure 1. Summary of Results Speed survey data was collected within the study corridor to determine the 85"‘ percentile speeds. The 85"‘ percentile speeds ranged from 34 to 35 miles per hour (mph). Based exclusively on the 85" percentile speeds, the recommended speed limit would be 30 mph throughout the corridor. The CalTrans guidelines for conducting engineering and traffic surveys allow for an additional 5 mph reduction to the speed, limit based on accident history and non-apparent roadway conditions. An engineering review of the corridor characteristics and accident data (summarized in Table 1) found that further reductions to the 85"‘ percentile speed are not warranted. Recommendations An engineering study of the accident data and non-apparent roadway conditions were considered in-conjunction with the measured 85"‘ percentile speed to determine the speed limit most appropriate for the safe and orderly flow of traffic on Arastradero Road. The recommended speed limit is 30 mph and primary supporting information are presented in Table 2. Fehr & Peers Associates City of.Palo Alto Speed Zones December 1997 Corridor Segments: IA-1 - El Camino Real to Foothill Expressway Figure 1 ARASTRADERO CORRIDOR EL CAMINO REAL TO FOOTHILL EXPRESSWAY Fehr & Peers Associates Not to Scale Engineering and Traffic Survey Report for Arastradero Road between El Camino Real and Foothill Expressway December 1997 Fehr & Peers Associates Engineering and Traffic Survey Report for Arastradero Road between El Camino Real and Foothill Expressway December 1997 - Table 2 Recommended Speed Limit Arastradero Road Arastradero Road Segment El Camino Real to Foothill Expressway Existing Speed Limit 25 85th Percentile Speed 34 Speed Limit based on 85th Percentile SpeedI 30 Accident Rate/ Roadway Conditions Information2 Below/No Median Speed of 10-mph Pace~ 29 Recommended Speed Limit 30 1. CalTrans guidelines require setting radar-enforceable speed limits at the 5 mph interval immediately below the 85~ percentile speed, unless accidents and/or non-apparent roadway conditions warrant further lowering. 2. See Table 1 for Accident Rate and Roadway Conditions Information 3. ITE emphasizes that the speed limit should not be set below the median spe~d of the 10-mph i~ace. The recommended 30 mph speed limit is higher than the existing 25 mph posted speed limit. The results of the speed surveys and evaluation of roadway conditions and accident history indicate that, to permit radar-enforcement, the speed limit should be raised to 30 mph. There is one school zone located along the Arastradero corridor between Georgia Avenue and Miranda Avenue. The school_zone is clearly marked and signed with 25 mph school speed zone signs. During school commuter periods (when children are present), radar may be used to enforce speeds within the school zone. Fehr & Peers Associates 4 II. Engineering and Traffic Survey Report for Arastradero Road between E1Camino Real and Foothill Expressway December 1997 " GENERAL INFORMATION This report conforms with the conditions of Section 627 - "Engineering and Traffic Survey" of the CVC which states that the fol!o~__ving fa_c_to_r_s shall be included for consideration: (1) (2) (3) Prevailing speeds as determined by traffic engineering measurements. Accident records. Highway, traffic, and roadside conditions not readily apparent to the driver. The method for conducting engineering and traffic surveys for City and County arterials, ¯ collectors, and local roads as described in._th_e. CalTrans Traffic Manual states that the speed limit should normally be established at the first five mile per hour increment below the 85th percentile speed. The 85~ percentile speed is the speed at or below which 85 percent of the motorists are driving. Speed limits higher than the 85th percentile speed are not generally considered reasonable or safe, and speed limits set too far below the 85’~ percentile speed do not facilitate the orderly movement of traffic. Speed limits established on this basis conform to the consensus of those who drive highways as to what speed is reasonable and safe, and are no.t dependent on the judgement of one or a few individuals. However, an engineering analysis of the accident history and roadway conditions may also indicate the need for a further five mph reduction in the speed limit indicated by the 85th percentile speed. Such a reduction could be based on one or more of the following factors: Most recent two year accident record Roadway conditions not readily apparent to drivers Roadway design speed Safe stopping sight distance Superelevation Shoulder conditions Profile conditions Intersection spacing and offsets Fehr & Peers Associates 5 Engineering and Traffic Survey Report for Arastradero Road between El Camino Real and Foothill Expressway December 1997 g.Driveway characteristics h.Pedestrian traffic i.Sidewalks The measurement of prevailing Speeds was done by a certified technician using a calibrated radar speed gun. The following procedures were followed for the measurements: ¯Locations were selected where prevailing speeds were representative of the entire speed~ zone. Areas near traffic control devices and horizontal and vertical curves were avoided. ¯Speed measurements were taken during off-peak hours on weekdays. ¯Weather was fair and the surveyor and radar, equipment were as inconspicuous as possible. i Angle to roadway centerline was no greater than 15 degrees in both directions. ¯The minimum survey sample was 100 vehicles. Fehr & Peers Associates 6 Engineering and Traffic Survey Report for Arastradero Road between El Camino Real and Foothill Expressway December 1997 III.ENGINEERING AND TRAFFIC SURVEYS The engineering and traffic surveys on Arastradero Road were conducted in accordance with Section 627 of the CVC and the CalTrans Traffic Manual. This survey includes the prevailing (85¢ percentile) speeds, accident rates, roadway conditions not readily apparent tO the driver, and recommendations. Prevailing Speeds The prevailing speed data consists of the 85~ percentile speeds, the 10-mph pace, and the median speed of the 10-mph pace. The prevailing speed data is presented in Table 3. Other factors pertaining to the prevailing speeds along the corridor are: The existing speed limit is 25 mph. Speed surveys were conducted on October 15th, 1997 between 9:00 and 11:00 a.m. (Refer to radar speed data in Appendix A). Table 3 Prevailing Speed Data ---Arastradero Road Segment El Camino Real to Foothill Expressway 85th Percentile Speed (mph) EB WB 34 35 10-mph Pace (mph) EB WB 25-34 28-37 Median of lO-mph Pace (mph) EB WB 29 32 The 85th percentile speed is higher than the posted speed limit in the study section on Arastradero Road. Based exclusively on the 85th percentile speeds, the indicated speed limit would be 30 mph throughout the study section. CalTrans guidelines allow that a review of the non-apparent roadway conditions and accident history may justify reducing the radar enforceable speed by an Fehr & Peers Associates 7 ¯ - Engineering and Traffic Survey Report for Arastradero Road between El Camino Real and Foothill Expressway December 1997 additional 5 mph below the 30 mph speed limit dictated by the 85th percentile measurements. Table 3 also illustrates the 10-mph pace and the median of the 10-mph pace along Arastradero Road. The 10-mph pace is the 10-mph increment of speed containing the largest number of vehicles. The Institute of Transportation Engineers advises against setting a speed limit below the median speed of the 10-mph pace, and research from the Transportation Research Board ’ indicates that setting the speed limit too far below the 85t~ percentile speed generally results in an increase in the number of accidents. Roadway Conditions Fehr & Peers Associates conducted field reconnaissance to identify the physical characteristics and land uses on Arastradero Road that may not be readily apparent to the driver. Information pertaining, to pavement geometry and alignment, land uses, driveway densities, bicycle and pedestrian activity, and other factors were collected. Arastradero Road is a four-lane, undivided roadway from El Camino Real to Foothill Expressway. Parking is permitted on the north side of the road from E1 Camino Real to Donald Drive. Separate bike lanes are provided on both sides of the road through the corridor. In the study section, the surrounding land use is primarily residential. The pavement is in fair condition and none of the observed roadway conditions warrant a further five mph reduction to the speed limit indicated by the 85a’ percentile speed. School zone speed limits are posted to protect children in school areas. The corridor has one school zone. The school zone is for the Henry Gunn High School and is located from west of Georgia Avenue to east of Miranda Avenue. The State of California’s statute for school zone speed limits is 25 mph. Although, the recommended radar-enforceable speed limit is higher than 25 mph, the 25 mph school zone speed limit could be enforced using radar within the school zone when children are present. i Fehr & Peers Associates 8 Engineering and Traffic Survey Report for - - Arastradero Road between El Camino Real and Foothill Expressway December 1997 " Accident History, The CalTrans Traffic Manual recommends that the most recent two-Year accident history be used to .calculate accident rates for determining radar-enforceable speed limits. For this ¯ engineering and traffic survey, the most,recent two-year rates (1995 and 1996) were used as the primary basis of determining the safety level of the street and setting the speed limits. Accident data from 1995 through 1996 was collected from the City of Palo Alto Police Department and summarized to determine the two-year accident rate. The accident rate is based on one million-vehicle-miles of travel and is an indicator of high accident locations. High accident locations are areas where the accident rate is higher than the average for other similar locations or conditions. Accidents not reported to the Pato Alto Police Departme’n-t-were not included. The accident rate for segments of roadway can be calculated by the equation: Accident Rate = (# of accidents x 1 million) / (total vehiq_l_e miles of travel) Typical four lane, urban roads in the Bay Area (CalTrans District 4) have an average accident rate of 3.97 per million-vehicle-miles traveled. The CalTrans District 4 accident rate for four lane, urban roadways was determined from CalTrans 1995 Accident Data on California State Highways. The calculated two-year average accident rate for the corridor is presented in Table Table 4 Two-Year Average Accident Rate Arastradero Road (1995 through 1996) Arastradero Road Segment El Camino Real to Foothill Expressway Number of Accidents 36 Average Daily Traffic 19,700 2-Year Average Accident Rate 2;36 Fehr & Peers Associates 9 Engineering and Traffic Survey Report for Arastradero Road between El Camino Real and Foothill Expressway December 1997 The low rate (less than 3.97) indicates that this section of roadway is below the Bay Area average in the frequency of accidents for similar four-lane roadways, and a further 5 mph reduction to the speed limit is not warranted. RecOmmendation Based on a review and analysis of speed survey data, roadway conditions, and accident history on Arastradero Road, a speed limit of 30 mph is justified and so recommended as the radar enforceable speed limit. Fehr & Peers AssOciates 10 APPENDIX A ARASTRADERO ROAD RADAR SPEED DATA BA YMETRICS TRAFFIC RESOURCES RADAR SPEED SURVEY PROJECT NAME: CITYWIDE SPEED LIMIT STUDY LOCATION: ARASTRADERO WEST OF SUZANNE SITE ID: A1 CITY: PALO A~,TO DATE:10/15/97 TIME:9AM- 11 AM DIRECTION: EASTBOUND FILE:3A1AM # 1 2 3 4 5 6 7 8 9 lO 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 SPEED 35 33 40 32 31 29 28 34 26 27 33 34 29 28 30 32 29 22 25 27 3O 26 28 33 34 PERCENTILE: SPEEDS: # 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 -47 48 49 5O 10% 24.9 SPEED 29 36 31 28 27 29 3O 33 29 26 28 33 34 32 28 28 27 3O 3O 28 31 34 33 29 29 15% 25.0 # 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68- 69 70 71 72 73 74 75 25% 27.0 SPEED 33 34 33 26 22 25 35 36 40 24 26 23 29 25 30 32 22 24 38 41 27 26 35 25 22 50% 29.0 # 76 77 78 79 80 81 82. 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 85% 34.0 SPEED 24 33 27 28 27 23 32 33 25 25 28- 27 31 32 22 29 31 32 34 29 26 33 28 27 26 90% 34.0 BA YMETRICS TRAFFIC RESOURCES RADAR SPEED SURVEY PROJECT NA_M~: CITYWlDE SPEED LIMIT STUDY LOCATION: ARASTRADERO WEST OF SUZANNE SITE lI): A1 CITY: PALO ALTO DATE:10/15/97 TIME:9AM-11 AM DIRECTION: WESTBOUND FILE:3A1 AM # 1 2 3 4 5 6 7 8 9 lO 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 SPEED 30 33 29 28 30 32 29 25 34 33 36 30 30 29 28 34 32 33 32 29 28 27 37 35 33 PERCENTILE: SPEEDS: # 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 5O 10% 2Z9 SPEED 29 31 26 28 27 22 25 34 33 36 33 35 29 29 30 30 32 31 32 29 28 28 31 34 29 15% 28.0 # 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 25% 29.0 SPEED 33 34 36 38 33 37 35 35 29 34 36 33 4O 35 35 41 33 37 29 28 33 26 28 25 50% 31.5 # 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 lO0 85% 35.0 SPEED 28 27 30 32 29 34 37 29 28 33 36 3O 28 37 35 32 33 28 3O 32 33 28 27 30 9O% 36.0 Final Report: CHARLESTON ROAD SPEED ZONE ANALYSIS Prepared for: City of Palo Alto Prepared by: Fehr & Peers Associates, In~ Transportal~on Consultan[s December 1997 971-1095 TABLE OF CONTENTS EXECUTIVE SUMMARY ...........................................1 Summary of Results .................................................1 Recommendations .........., ........................................1 II. III. GENERAL INFORMATION .........................................5 ENGINEERING & TRAFFIC SURVEYS ...............................7 Prevailing Speeds .......................................................7 Roadway Conditions ................................................8 Accident History ...................................................9 Recommendation ..................................................11 1 Charleston Road Corridor ............................................2 Tables 1 2 3 Roadway Conditions and AccidentRate Information .......................3 Recommended Speed Limits ..........................................4 Prevailing Speed Data ......................................~ ........7 Two-Year Average Accident Rates ....................................10 Appendix Appendix A - Radar Speed Data Engineering and Traffic Survey Report for Charleston Road from El Camino Real to San Antonio Road December 1997 . -EXECUTIVE SUMMARY Fehr & Peers Associates, Inc. was retained by the City of Palo Alto to conduct a speed zone analysis for a 2.5 mile section of Charleston Road. The intent of this study was to conduct an engineering and traffic survey consistent with the California Vehicle Code (CVC) and CalTrans guidelines for consideration by the City Council to post speed limits which could be enforced by using radar. The segment of Charleston Road from San Antonio Road to E1 Camino Real was divided into three subsections for this speed survey. The study~orfidor and corresponding subsections are illustrated in Figure 1. "Summary of Results Speed survey data was collected in each subsection to determine the 85ta percentile speeds. The 85¢ percentile speeds ranged from 35 to 36 miles per hour (mph). Based exclusively on the 85th percentile speeds, the recommended speed limit would be 35 mph throughout the corridor. The CalTrans guidelines for conducting engineering and traffic surveys allow for an additional-5 mph reduction to the speed limit based on accident history and non-apparent roadway conditions. An engineering review of the corridor characteristics and accident data (summarized in Table 1) found that further reductions to the speed limit indicated_by the 85th percentile speed were warranted on Charleston Road between Middlefield Road and San Antonio Road. Recommendations An engineering study of the accident data and non-apparent roadway conditions were considered in conjunction with the 85th percentile speed and 10-mph pace speed to determine the speed limit most appropriate for safe and orderly flow of traffic on Charleston Road. The recommended speed limits and primary supporting information are presented in Table 2. Fehr & Peers Associates 1 City of Palo Alto Speed Zones December 1997 Corridor Segments: Col - El Camino Real to Alma Street C-2 - Alma Street to Middlefield Road C-3 - Middlefield Road to San Antonio Road Figure I CHARLESTON CORRIDOR EL CAMINO REAL TO SAN ANTONIO ROAD Fehr & Peers Associates Not to Scale Engineering and Traffic Survey Report for Charleston Road.from El Camino Real to San Antonio Road December 1997 Fehr & Peers Associates _3 Engineering and Tra.Oqc Survey Report for Charleston Road from El Camino Real to San Antonio Road December 1997 Table 2 Recommended Speed Limits Charleston Road Charleston Road Segment El Camino Real to Alma Street Existing Speed Limit 25 Percentile Speed 36 Speed Limit based on 85*h Percentile Speedt 35 Accident Rate/ Roadway Conditions2 - Below/No Median Speed of 10-mph Pace3 32 Recommended Speed Limit Alma Street to 25 36 35 Above/No 32 35Middlefield Road Middlefield Road to 25 35 35 Above/No 30 30San Antonio Road 1. CalTrans guiddlines require setting radar-enforceable speed limits at the 5 mph interval immediately below,the 85th percentile speed, unless accidents and/or non-apparent roadway conditions warrant further lowering. 2. See Table I for Accident Rate and Roadway Conditions Information 3. ITE emphasizes that the speed limit should not be set below the median speed of the 10-mph pace. The recommended 30 and 35 mph speed limits are higher than the existing 25 mph posted speed limit. The results of the speed surveys and evaluation of roadway conditions and. accident history indicate that, to permit radar-enforcement, the speed limit should be raised to 30 mph east of Middlefield Road and 35 mph west of Middlefield Road. There is one school zone located along the Charleston corridor between Middlefield Road and Carlson Circle. The school zone is clearly marked and signed with 25 mph school speed zone signs. During school commuter periods (when children are present), radar may be used to enforce speeds within the school zone. Fehr & Peers Associates 4 II. Engineering and Traffic Survey Report for Charleston Road from El Caraino Real to San Antonio Road Dec~inber 1997 GENERAL INFORMATION This report conforms with the conditions of Section 627 - "Engineering and Traffic Survey" of the CVC which states that the following factors shall be included for consideration: (1) (3) Prevailing speeds as determined by traffic engineering measurements. Accident records. Highway, traffic, and roadside conditions not readily apparent to the driver. The method for conducting engineering and traffic surveys for City and County arterials, collectors, and local roads as described in the CalTrans Traffic Manual states that the speed limit should normally be established at the first five mile per hour increment below the 85t~ percentile speed. ~The 85th percentile speed is the speed at or below which 85 percent of the motorists are driving. Speed limits higher than the 85~ percentile speed are not generally considered reasonable o~ safe, and speed limits set too far below the 85th percentile speed do not facilitate the orderly movement of traffic. Speed limits established on this basis conform to the consensus of those who drive highways as to what speed is reasonable and safe, and are not dependent on the judgement of one or a few individuals. However, an engineering analysis of the accident history and roadway conditions may also indicate the need for a further five mph reduction in the speed limit indicated by the 85th percentile speed. Such a reduction could be based on one or more of the following factors: Most recent two year accident record Roadway conditions not readily apparent to drivers a.Roadway design speed b.Safe stopping sight distance c.Superelevation d.Shoulder conditions e.Profile conditions f.Intersection spacing and offsets Fehr & Peers Associates Engineering and Tra.l~qc Survey Report for Charleston Road from El Camino Real to San Antonio Road December 1997 - - g.Driveway characteristics h.Pedestrian traffic i.Sidewalks The measurement of prevailing speeds was done by a certified technician using a calibrated radar speed gun. The following procedures were followed for the measurements: ¯Locations were selected where prevailing speeds were representative of the entire speed zone. Areas near traffic control devices and horizontal and vertical curves were avoided. ¯Speed measurements were taken during off-peak hours on weekdays. ¯Weather was fair and the surveyor and radar equipment were inconspicuous. ¯Angle to roadway centerline was no greater than 15 degrees in both directions. ¯The minimum survey sample was 100 vehicles in each direction. Fehr & Peers Associates 6 Engineering and Traffic Survey Report for Charleston Road from El Camino Real to San Antonio Road " Dedember 1997 - III. ENGINEERING AND TRAFFIC SURVEYS The engineering and traffic surveys on Charleston Road were conducted in accordance with Section 627 of the CVC and the CalTrans Traffic Manual. This survey includes the prevailing (85~ percentile) speeds, accident rates, roadway conditions not readily apparent to the driver, and recommendations. Prevailing Speeds The prevailing speed data consists of the 85th percentile-speeds, the 10-mph pace, and the median .speed of the 10-mph pace. The prevailing speed data is presented in Table 3. Other factors pertai~aing to the prevailing speeds along the corridor are: The existing speed limit is 25 mph. Speed surveys were conducted on October 15t~, 1997, between 9:00 and 11:00 a.m. (Refer to radar speed data in Appendix A). - - Table 3 Prevailing Speed Data Charleston Road Segment El Camino Real to Alma Street Alma Street ~o Middlefield Road Middlefield Road to San Antonio Road 85th Percentile Speed (mph) EB WB 36 36 36 36 35 36 10-mph Pace (mph)- Median of 10-mph Pace (mph) EB WB 32 32 32 33 30 32 EB WB 26-35 28-37 27-36 28-37 26-35 27-36 In all of the subsections on Charleston Road, the 85th percentile speed is higher than the posted speed limit. Based exclusively on the 85th percentile speeds, the indicated speed limit would be Fehr & Peers Associates 7 Engineering and Tra~c Survey Report for Charleston Road from El Camino Real to San Antonio Road December 1997 . 35 mph throughout the study corridor. CalTrans guidelines allow that a review of the non- apparent roadway conditions and accident history may justify reducing the radar enforceable speed by an additional 5 mph below the 35 mph speed limit dictated by the 85th percentile speed measurements. Table 3 also illustrates the 10-mph pace and the median of the 10-mph pace along Charleston Road. The 10-mph pace is the 10-mph increment of speed containing the largest number of vehicles. The Institute of Transportation Engineers advises against seX~g a speed limit below the median speed of the 10-mph pace, and research from the Transportation Research Board indicates that setting the speed limit too far below the 85t~ percentile speed generally results in an increase in the number of accidents. Roadway Conditions Fehr & Peers Associates conducted field reconnaissance to identify the physical characteristics and land uses on Charleston Road that may not be readily apparent to the driver. Information pertaining to pavement geometry and alignment, land uses, driveway densities, bicycle and pedestrian activity, and other factors were collected. Charleston Road is a four-lane, undivided roadway from El Chmino Real to San Antonio Road. Parking is restricted at certain sections along the corridor. Separate bike lanes are provided from Middlefield Road to El Camino Real. The surrounding land use is primarily residential with some commercial blocks toward the east end of the corridor. The pavement is in fair condition and there are none of the observed roadway conditions warrant a further five mph reduction to the speed limit indicated by the 85th percentile speed. ¯School zone speed limits are posted to protect children in school areas. The corridor has one school zone from east of Middlefield Road to west of Carlson Circle. The State of California’s statute for school zone speed limits is 25 mph. Although, the recommended radar-enfrrceable Fehr & Peers Associates 8 Engineering and Traffic Survey Report for " Charleston Road from El Camino Real to San Antonio Road ~ December 1997 ¯ -- " speed limits are higher than 25 mph throughout the corridor, the 25 mph school zone speed limit could be enforced using radar within the school zone when children are present. Accident History The CalTrans Traffic Manual recommends that the most recent two-year accident history be used to calculate accident rates for determining radar-enforceable speed limits. For this engineering and traffic survey, the most recent two-year rates (1995 and 1996) were used as the primary basis of determining the safety level of the street and setting the speed limits. Accident data from 1995 through 1996 was collected from the City of Palo Alto Police Department and summarized to determine the two-year accident rates of each subsection. The accident rate is based on one million-vehicle-miles of travel and is an indicator of high accident locations. High accident locations are areas where the accident rate is higher than the average for other similar locations or conditions. Accidents not reported to the Palo Alto Police Department were not included. The accident rate for segments of roadway can be calculated by the equation: Accident Rate = (# of ace]dents x 1 million) / (total vehicle miles of travel) Typical four lane, urban roads in the Bay Area (CalTrans District 4) have an average accident rate of 3.97 per million-vehicle-miles traveled. The CalTrans District 4 accident rate for four lane, urban roadways was determined from CalTrans 1995 Accident Data on California State Highways. The calculated two-year average accident rates for each segment of the corridor are presented in Table 4. Fehr & Peers Associates 9 Engineering and Traffic Survey Report for Charleston Road from El Camino Real to San Antonio Road Deceinber 1997 - " Table 4 Two-Year Average Accident Rates Charleston Road (1995 through 1996) Charleston Road Segment El Camino Real to Alma Street Alma Street to Middlefield Road Middlefield Road to San Antonio Road __.IS_umber of Accidents 8 23 22 Average Daily Traffic 16,100 13,100 10,900 2-Year Average Accident Rate 1.75 4.15 5.53 ,The second and tlMrd subsections exceed the Bay Area (CalTrans District 4) average accident rate of 3.97 accidents per million-vehicle-miles traveled indicating that the speed limit in these subsections could be reduced-by an additional 5 mph. CalTrans guidelines emphasize that establishing a speed limit by more than 5 mph below the 85~ percentile speed should be done with great care to prevent setting the speed limit which is below that traveled by the majority of drivers and making violators of a disproportionate number. Furthermore, research from the Transportation Research Board indicates that setting the speed limit too far below the 85t~ percentile speed generally results in an increase in the number of accident, and the Institute of Transportation Engineers advises against setting the speed limit below the median speed of the 10-mph pace. To determine whether a subsection should be reduced to 30 mph, a review was made to see if the reduced speed limit would be below the median of the 10-mph pace. This review was applicable to the subsections from Alma Street to Middlefield Road and Middlefield Road to San Antonio Road, where the accident rates were 5% and 39% above the Bay Area average accident rate, respectively. A speed limit reduction to 30 mph was considered on each section. However, a 30 mph speed limit would be below the median of the 10-mph p_a__c_e for the corridor segment between Alma Street and Middlefield Road and would make violators of a disproportionate number of Fehr & Peers Associates 10 Engineering and Traffic Survey Report for Charleston Road from El Camino Real to San Antonio Road December -1997 . drivers in this subsection. For the subsection from Middlefield Road to San Antonio Road, the median of the 10-mph pace was 30 mph. Therefore, the speed limit was reduced to 30 mph on this subsection, since it is not below the median speed of the 10-mph pace. Recommendation Based on a review and analysis of speed survey data, roadway conditions, and accident history on Charleston Road, a speed limit of 35 mph from the E1 Camino Real to Middlefield Road and a speed limit of 30 mph from Middlefield Road to San Antonio Road are justified and so recommended as the radar enforceable speed limits. Fehr & Peers Associates 11 APPENDIX A CHARLESTON ROAD RADAR SPEED DATA BA YME TR ~ CS RADAR T,~AFFIC REdO UR CES SPEED SURVEY PROJECT NAME: CITYWIDE SPEED LIMIT STUDY DATE:10/15/97 LOCATION: CHARLESTON ROAD WEST OF WILKIETIME:9 AM - 11 AM SITE ID: C1 DIRECTION: EASTBOUND CITY: PALO ALTO FILE:3CLAM . I I sr, r r r,I . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 32 32 29 35 40 26 33 35 29 35 36 34 33 32 30 29 28 33 34 35 31 33 30 35 26 PER CENTILE: SPEEDS: 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 10% 27.9 29 33 34 28 34 32 29 25 28 33 36 38 41 35 36 42 33 37 35 39 35 29 28 31 32 15% 28.0 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 25% 29.0 28 27 26 33 35 35 32 26 29 33 34 34 40 29 33 38 41 29 28 33 35 34 28 26 29 50% 33.0 76 77 78 79 8O 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 8.$% 36.0 33 35 34 30 32 28 27 29 33 35 34 42 25 32 27 30 33 37 36 33 38 32 35 34 33 90% 37.1 BA YMETRICS ,TRAFFIC RADAR SPEED S PROJECT NAME: CITYWIDE SPEED LIMIT STUDY LOCATION: CHARLESTON ROAD WEST OF WILKIE DATE:10/15/97 TIME:9 AM- 11 AM SITE ID: C1 DIRECTION: ’WESTBOUND CITY: PALO ALTO FILE:3CLAM I #SPEEDI #SPEED #SPEED# 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 33 17 36 18 40 19 38 20 35 21 39 22 35 23 29 24 28 25 22 PERCENTILE: SPEED 32 29 30 32 35, 38 36 33 30 29 28 31 34 42 38 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 10% 28.0SPEEDS: 35 31 33 2"9 31 32 33 30 32 28 29 37 36 40 35 32 29 28 33 35 31 35 38 33 36 15% 28.0 51 54 55 56 57 58 59 60 61 62 63 64. 65 66 67 68: 69 70 71 72 73 74 75 25% 29.0 37 33 29 28 30 .28 30 28 27 26-- 35 34 26 32 22 28 28 29 33 34 32 36 40 29 35 :50% 32.0 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 85% 36.0 33 37 36 33 34 29 28 -30 32 25 28 29 33 34 26 29 33 32 24 28 28 33 34 32 33 90% 37.0 BA YME TR I C S RADAR PROJECT NAME: LOCATION: TRAFFIC RESOURCES SPEED SURVEY CITYWIDE SPEED LIMIT STUDY DATE: CHARLESTON ROAD EAST OF CARLSON TIME: 10/15/97 9AM- 11 AM SITE I-D: C2 DIRECTION: EASTBOUND CITY: PALO ALTO FILE:3C2AM I#SPEED |# 26134 2 35 3 33 4 29 5 31 6 32 7 29 8 28 9 30 10 28 11 33 12 26 13 28 14 27 15 30 16 35 17 33 18 34 19 36 20 29 21 36 22 34 23 28 24 32 25 33 PERCENTILE: SPEEDS: ° 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 10% 27.9 SPEED 28 29 27 30 35 33 35 36 33 41 30 30 29 28 28 34 32 33 36 29 29 25 35 33 34 15% 28.0 I # 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 --67 68 69 70 71, 72 73 74 75 25% 29.0 SPEED 31 32_. 28 29 36 29 26 28 30 30 32 28 27 26 33 34 32 29 28 38 37 30 29 35 34 50% 32.0 # 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 I00 85% 36.0 SPEED 33 29 32 26 25 42 35 38 36 30 33 40 41 38 37 33 36 32 26 29 30 31 32 33 35 90% 36.0 BA YMEI, TRICS RADAR TRAFFIC RESOURCES SPEED SURVEY ~ PROJECT NAME: CITYWIDE SPEED LIMIT STUDY DATE: LOCATION: CHARLESTON ROAD EAST OF CARLSON TIME: SITE ID: C2 CITY: PALO ALTO , I 2 3 4 5 6 7 8 9 # 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 PERCENTILE: SPEEDS: , SPEED 26 29 33 34 28 30 34 35 29 26 33 32 28 28 27 31 26 3O 32 26 3O 28 29 33 34 10% 28.0 SPEED 35 40 42 35 38 41 38 36 33 35 35 34 33 29 36 34 35 37 33 32 29 28 3O 33 32 15% 28.0 # 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 25% 29.0 10/15/97 9AM- 11 AM DIRECTION: WESTBOUND FILE:3C2AM SPEED 29 28 35 34 33 31 30 29 29 28 30 34 34 33 36 35 37 42 38 33 36 29 40 35 41 50% 33.0 #SPEED 76 29 77 25 78 25 79 26 80 27 81 33 82 35 83 36 84 37 85 33 86 35 87 34 88 38 89 29 90 29 91 31 92 34 93 33 94 38 95 36 96 42 97 36 98 36 99 35 1 O0 ~29--- 85%90% 36.2 38.0 BA YME TRICS RADAR TRAFFIC SPEED S RESOURCES URVEY PROJECT NAME: CITYWIDE SPEED LIMIT STUDY LOCATION: CHARLESTON ROAD EAST OF GROVE SITE ID: C3 CITY: PALO ALTO DATE:10/15/97 TIME:9 AM - 11 AM DIRECTION: EASTBOUND FILE:3C3AM # 1 - 2 3 4 5 6 7 8 9 10 11 12 13 14 __ 15 16 17 18 19 20 21 22 23 24 25 PER CENTILE: SPEEDS: # 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40. 41 42 43 44 45 46 47 48 49 50 SPEED 33 29 28 30. 28 34 32 28 33 36 34 35 28 28 34 35 37 31 30 32 35 28 29 33 35 10% 27,0 SPEED 25 28 33 34 36 37 35- 40 32 28 29 31 32 33 34 29 28 30 32 31 35 36 30 29 28 15% 28.0 I # 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 25% 28.0 SPEED 34 32 33 28 29 37 40 35 33 36 38 29 28 27 26 34 32 28 ’29 33 34 26 25 -~27 29 50% 31.0 # 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 85% 35.0 SPEED 28 27 26 30 30 31 35 32 28 27 26 35 33 35 29 28 27 30 30 35 32 28 29 27 26 90% 35.1 BA YME TRICS RADAR TRAFFIC RESO UR CES SPEED SURVEY PROJECT NAME: CITYWIDE SPEED LIMIT STUDY LOCATION: CHARLESTON ROAD EAST OF GROVE SITE ID: C3 CITY: PALO ALTO DATE:10/15/97 TIME:9 AM - 11 AM DIRECTION: WESTBOUND FILE:3C3AM 1 34 26 34 51 - 44 76 31 2 33 27 33 52 26 77 32 3 36 28 36 53 34 78 30 4 29 29 35 54 38 79 32 5 28 30 35 55 36 80 33 6 30 31 42 56 40 81 29 7 35 32 35 57 42 82 28 8 33 33 38 58 35 83 27 9 38 34 35 59 29 84 29 10 36 35 36 60 28 85 26 11 35 36 40 61 36 86 35 12 34 37 42 62 34 87 25 13 32 38 37 63 28 88 28 14 29 39 29 64 27 89 27 15 28 40 38 --65 29 90 26 16 22 41 31 66 29 91 33 17 25 42 32 67 36 92 34 18 34 43 29 68 33 93 30 19 31 44 28 69 32 94 28 20 29 45 33 70 25 95 27 21 28 46 34 71 26 96’29 22 28 47 38 72 28 97 30 23 41 48 35 73 27 98 32 24 28 49 35 74 26 99 33 25 42 50 42 75 35 lO0 26 PERCENTILE:10%15%25%50%85%90% SPEEDS:26. 9 2 Z 9 28. 0 32. 0 3~2 38. 0 Final Report: EMBARCADERO ROAD SPEED ZONE ANALYSIS Prepared for: City of Palo Alto_ Prepared by: Fehr & Peers Assodates, In~ Transportation Consultants December 1997 971-1095 II. III. TABLE OF CONTENTS EXECUTIVE SUMMARY ...........................................1 Summary of Results .................................................1 Recommendations .............................................~ ....1 GENERAL INFORMATION .........................................5 ENGINEERING & TRAFFIC SURVEYS ...............................7 Prevailing Speeds ....................................................7 Roadway Conditions ...~ .............................................8 Accident History ...........:-::--=. ...................................9 Recommendation ..................................................11 Figures 1 Embarcadero Road Corridor .............- .............................2 1 2 3 4 Engineering Factors and Accident Rate Information ........................3 Recommended Speed Limits ..........................................4 Prevailing Speed Data ..........................~. ....................7 Two Year Average Accident Rates ....................................10 Appendix Appendix A - Radar Speed Data Engineering and Traffic Survey Report fo-r Embarcadero Road from Alma Street to St. Francis Drive December 1997 " EXECUTIVE SUMMARY Fehr & Peers Associates, Inc. wag retained by the City of Palo Alto to conduct a speed zone analysis for a 1.7-mile section of Embarcadero Road. The intent of this study was to conduct an engineering and traffic survey consistent with the California Vehicle Code (CVC) and CalTrans guidelines for consideration by the City Council.to post sbeed limits which could be enforced by using radar. The section of Embarcadero Roa-d from Alma Street to St. Francis Drive was divided into three subsections for this speed survey. The study corridor and corresponding subsections are illustrated in Figure 1. Summary of Results Speed survey data was collected in each subsection to determine the 85th percentile speeds. The 85th percentile speeds ranged from 33 to 37 miles per hour (mph). Based exclusively on the 85th percentile speeds, the recommended speed limit would be 30 mph from Alma Street to Walnut Drive and 35 mph from Walnut Drive to St. Francis Drive. The CalTrans guidelines for conducting engineering and traffic surveys allow for an additional reduction of 5 mph to the speed limit based on accident history and non-apparent roadway conditions. An engineering review of the corridor characteristics and accident data (summarized in Table 1) found that further reductions to the speed limit were not warranted. Recommendations An engineering study of the accident data and non-apparent roadway conditions were considered in conjunction with the measured 85th percentile speed and the median speed of the 10-mph pace to determine the speed limit most appropriate for the safe and orderly flow of traffic on Embarcadero Road. The recommended speed limits and primary supporting information are presented in Table 2. Fehr & Peers Associates ~1 City of Palo Aito Speed Zones. December 1997 Corridor Segments: E-1 - Alma Street to Middlefield Road E-2 - Middlef~d Road to Walnut Drive E-3 - Walnut Drive to St Francis Drive Figure I Not to Scale EMBARCADERO CORRIDOR =ALMASTREETTOSTFRANCIS DRIVE Fehr & Peers Associates Engineering and Traffic Survey Report for Embarcadero Road from Alma Street to St. Franci~ Drive December 1997 Fehr & Peers Associates Engineering and Traffic Survey Report for Embarcadero Road from Alma Street to St. Francis Drive December 1997 Table 2 Recommended Speed Limits Embarcadero Road Embarcadero Road Segment Alma Street to Middlefield Road Existing Speed Limit Percentile Speed Speed Limit based on 85th Percentile SpeedI Accident Rate/ Roadway Conditions2 Median Speed of 10-mph Pace3 Recommended Speed Limit 25 33 30 Above/No 29 -30 Middlefield Road to 25 33 30 Below/No 29 30Walnut Drive Walnut Drive to 25 35 35 Below/No 32 35St. Francis Drive 1. CalTrans guidelines require setting radar-enforceable speed limits at the 5 mph interval immediately below the 85~ percehtile speed, unless accidents and/or non-apparent roadway conditions warrant further lowering. 2. See Table 1 for Accident Rate and Roadway Conditions Information 3. ITE emphasizes that the speed limit should not be set below the median speed of the 10-mph pace. The recommended 30 to 35 mph speed limits are higher.than the existing 25 mph posted speed limit. The results of the speed surveys and evaluation of roadway conditions and the accident history indicate that, to permit radar-enforcement, the speed limit should be raised to 30 mphfrom ¯ Alma Street to Walnut Drive and 35 mph from Walnut Drive to St. Francis Drive. There are two schools zone located along the Embarcadero corridor. One school zone is for the Castilleja School and is located from east of Emerson Street to west of Waverley Street, and the second school zone is for the Walter Hayes School and is located from east of Byron Street to west of Fulton Street. The school zones are clearly marked and signed with 25 mph school speed zone signs. During school commuter periods (when children are present), radar may be used to enforce speeds within the school zones. Fehr & Peers Associates 4 II. Engineering and Tra.ff~c Survey Report for Embarcadero Road from Alma Street to St. Francis Drive December 1997 - GENERAL INFORMATION This report conforms with the conditions of Section 627 - "Engineering and Traffic Survey" of the CVC which states that the following factors shall be included for consideration: (1) (2) (3) Prevailing speeds as determined by traffic engineering measurements. Accident records. Highway, traffic, and roadside conditions not readily apparent to the driver. The method for conducting engineering and traffic surveys for City and County artedals, .collectors, and local roads as described in the CalTrans Traffic Manual states that the speed limit should normally be established at the first five mile per hour increment below the 85t~ percentile~ speed. The 85th percentile speed is the speed at or below which 85 percent of the motorists are driving. Speed limits higher than the 85th percentile speed are not generally considered reasonable or safe, and speed limits set too far below the 85th percentile speed do not facilitate the orderly movement of traffic. Speed limits established on this basis conform to the consensus of those who drive highways as to what speed is reasonable and safe, and are not dependent on the judgement of one or a few individuals. However, an engineering analysis of the accident history and roadway conditions may also indicate the need for a further five mph reduction in the speed limit indicated by the 85th percentile speed. Such a reduction could be based on one or more of the following factors: Most recent two year accident record Roadway conditions not readily apparent to drivers Roadway design speed Safe stopping sight distance Superelevation Shoulder conditions Profile conditions Intersection spacing and offsets Fehr & Peers Associates 5 g.Driveway characteristics h.Pedestrian traffic i.Sidewalks Engineering and Traffic Survey Report for Embarcadero Road from Alma Street to St. Francis Drive. December 1997 - The measurement of prevailing speeds was done by a certified technician using a calibrated radar speed gun. The following procedures were followed for the measurements: Locations were selectedwhere pre~,,ailing speeds were representative of the entire speed zone. Areas near traffic control devices and horizontal and vertical curves were avoided. Speed measurements were taken during off-peak hours on weekdays. Weather was fair and the surveyor and radar equipment were inconspicuous. Angle to roadway centerline was no greater than 15 degrees in both directions. The minimum survey sample was 100 vehicles in each direction Fehr & Peers Associates 6 III. Engineering and Traffic Survey Report for Embarcadero Road from Alma Street to St. Francis Drive December 1997 . ENGINEERING AND TRAFFIC SURVEYS The engineering and traffic surveys on Embarcadero Road were conducted in accordance with Section 627 of the CVC and the CalTrans Traffic Manual. This survey includes the prevailing speeds, accident rates, roadway conditions not readily apparent to the driver, and recommendations. Prevailing Speeds The prevailing speed data consists of the 85th percentile spe~ds, the 10-mph pace, and the median speed of the 10-mph pace. The prevailing speed data is presented in Table 3. Other factors igertaining to the prevailing speeds along the corridor are: ¯The existing speed limit is 25 mph. ¯Speed surveys were conducted on October 15~, 1997, between 9:00 and 11:00 a.m. (Refer to radar speed data in Appendix A). Table 3 Prevailing Speed Data Embarcadero Road 85‘h Percentile Speed (mph) lO-mph Pace (mph) Median of lO-mph Pace (mph) Segment Alma Street to Middlefield Road Middlefield Road to Walnut Drive Walnut Drive to St. Francis Drive EB 35 33 35 WB 33 35 37 EB WB 28-37 25-34 25-34 26-35 27-36 28-3’7 EB WB 32 29 29 30 32 33 In all of the subsections on Embarcadero Road, the 85~ percentile speed is higher than the posted speed limit. Based exclusively on the 85th percentile speeds, the indicated speed limit would be Fehr & Peers Associates 7 Engineering and Traffic Survey Report for Embarcadero Road from Alma Street to St. Francis Drive December 1997 - 30 mph from the Alma Street to Walnut Drive and 35 mph from Walnut Drive to St. Francis Drive. CalTrans guidelines allow that a review of the non-apparent roadway conditions and accident history may justify reducing the radar enforceable speed by an additional 5 mph below the 30 and 35 mph speed limits dictated by the 85t~ percentile speed measurements. Table 3 also illustrates the 10-mph pace and the median of the 10-mph pace along Embarcadero Road. The 10-mph pace is the 10-mph increment of speed containing the largest number of vehicles. The Institute of Transportation Engineers advises against setting a speed limit below the median speed of the 10-mph pace, and research from the Transportation Research Board indicates that setting the speed limit too far below the 85th percentile speed generally results in an increase in the number of accidents. Roadway Conditions Fehr & Peers Associates conducted field reconnaissance to identify the physical characteristics and land uses on Embarcadero Road that may not be readily apparent to the driver. Information pertaining to pavement geo_metry and alignment, land uses, driveway densities, bicycle and pedestrian activity, and other factors were collected. Embarcadero Road has a continuous four-lane, undivided roadway from Alma Street to St. Frances Drive. Parking is permitted on Embarcadero Road east of Newell Road. No bike lanes are provided along the study corridor and the surrounding land use is primarily residential with some commercial blocks toward the east end of the study section. The pavement is in fair condition with no sharp horizontal or vertical curves. None of the observed roadway conditions warrant a further five mph reduction to the speed limit indicated by the 85th percentile speed. School zone speed limits are posted to protect children in school areas. There are two school zones in the corridor study area. The State of California’s statute for school zone speed limits is 25 mph. Although, the recommended radar-enforceable speed limits are higher than-25 mph Fehr & Peers Associates 8 Engineering and Traffic Survey Report for Embarcadero Road from Alma Street to St. Francis Drive December 1997 throughout the corrido~r, the 25 mph school zone speed limit could be enforced using radar within the school zone when children are present Accident History The CalTrans Traffic Manual recommends that the most recent two-year accident history be used to calculate accident rates for determining radar-enforceable speed limits. For this engineering and traffic survey, the most recent two-year rates (1995 and 1996) were used as the primary basis of determining the safety level of the street and setting the speed limits. Accident data from 1995 through 1996 was collected from the City of Palo Alto Police Department and summarized to determine the two-year accident rates of each subsection. The accident rate is based on one million-vehicle-miles of travel and is an indicator of high accident locations. High accident locations are areas where the accident rate is higher than the average for other similar locations or conditions. Accidents not reported to the Palo Alto Police Department were not included. The accident rate for segments of roadway can be calculated by the equation: Accident Rate = (# of accidents x 1 million) / (total vehicle miles of travel) Typical four lane, urban roads in the Bay Area (CalTrans District 4) have an average accident rate of 3.97 per million-vehicle-miles traveled. The CalTrans District 4 accident rate for four lane, urban roadways was determined from CalTrans 1995 Accident Data on California State Highways. The calculated two-year average accident rates for each segment of the corridor are presented in Table 4. Fehr & Peers Associates 9 Engineering and Traffic Survey Report for Embarcadero Road.from Alma Street to St. Francis Drive December 1997 - Table 4 Two-Year Average Accident Rates Embarcadero Road (1995 through 1996) Embarcadero Road Segment Alma Street to Middlefield Road Middlefi~ld Road to Walnut Drive ’ Walnut Drive to St. Francis Drive Number of Accidents 56 24 32 Average Daily Traffic --24,000- 26,8.00 24,600 ¯2-Year Average Accident Rate 4.26 3.41 3.02 The two-year average accident rate on the first subsection exceeds the Bay Area (CalTrans District "4) average accident rate of 3.97 accidents per million-vehicle-miles traveled indicating that the speed limit in this subsection could be reduced by an additional 5 mph. However, CalTrans guidelines emphasize that establishing a speed limit by more than 5 mph below the 85th percentile speed should be done with great care to prevent setting the speed limit which is below that traveled by the majority of drivers and making violators of a disproportionate number. Furthermore, research from the Transportation Research Board indicates that setting the speed limit too far below the 85th percentile speed generally results in an increase in the number of accidents, and the Institute of Transportation Engineers advises against setting the speed limit below the median speed of the 10-mph pace. Reducing the speed by an additional 5 mph, would place the speed limit below the median of the 10-mph pace. On the subsection from Alma Street to Middlefield Road where the calculated accident rate exceeds the Bay Area average, a speed limit reduction to 25 mph would place the’ speed limit below the median speed (29 mph) of the 10-mph pace and would make violators of a disproportionate number of drivers (over 90%). Therefore, the speed limit could not be reduced below the recommended 30 mph for this subsection. Fehr & Peers Associates _10 Engineering and Traffic Survey Report for Embarcadero Road from Alma Street to St. Francis Drive December 1997 Recommendation Based on review and analysis of speed survey data, roadway conditions and accident history on Embarcadero Road, a speed limit of 30 mph from the Alma Street to Walnut Drive and a speed limit of 35 mph from Walnut Drive to St. Francis Drive are justified and so recommended as the radar enforceable speed limits. Fehr & Peers Associates 11 APPENDIX A EMBARCADERO ROAD RADAR SPEED DATA BA YMETRICS TRAFFIC RESOURCES RADAR SPEED SURVEY PROJECT NAME: CITYWIDE SPEED LIMIT STUDY DATE:10/15/97 LOCATION: EMBARCADERO WEST OF CHURCHILL TIME:9 AM - 11 AM SITE ID: E1 DIRECTION: EASTBOUND CITY: PALO ALTO FILE:3E1AM # 1 2 3 4 5. 6 7 8 9 I0 11 12 13 1~4 15 16 17 18 19 20 21 22 23 24 25 SPEED 32 28 30 35 34 41 28 29 33 35 36 34 35 29 28 33 29 28 33 31 32 30 42 41 38 PERCENTILE:25% SPEEDS:29.0 36.1 # 26 27. 28 29 30 31 32 33 34. 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 lO% 28.0 SPEED 35 33 29 28 30 32 33 34 34 29 28 33 32 30 32 29 28 34 38 37 36 33 35 42 33 15% 28.0 #i SPEED 51 35 52 38 - 53 36 54 35 55 33 56 29 57 29 58 28 59 30 60 31 61 32 62 33 63 35 64 ,~35 65 29 66 26 67 28 68 30 69 27 70 29 71 33 72 34 73 41 74 35 75 32 50% 32.0 # 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92-~ 93 94 95 96 97 98 99 100 85% 35.0 SPEED 26 28 29 30 32 35 36 37 35 22 29 29 28 30 32 22 26 29 33 34 28 32 31 30 28 90% BA YME TRICS RADAR TRAFFIC RESOURCES SPEED SURVEY PROJECT NAME: CITYWIDE SPEED LIMIT STUDY LOCATION: EMBARCADERO WEST OF CHURCHILL SITE ID: E1 CITY: PALO ALTO DATE:10/15/97 TIME:9 A.M- 11 AM DIRECTION: WESTBOUND FILE:3E1AM 1 2 3 4 5 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 SPEED ¯ 25 33 29 28 30 31 33 28 28 27 30 35 28 26 31 33 29 34 3O 28 25 24 29 31 ! :32 PERCENTILE: SPEEDS: # 26 27 28 29 3O 31 32 33 34 35 36 37 38 39 4O 41 42 43 44 45 46 47 48 49 5O 10% 25.9 SPEED 30 29 28 35 32 33 28 27 26 25 20 19 25 24 28 29 30 33 32 28 27 26 33 31 32 15% 27.0 # 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 25% 28.0 SPEED 29 31 30 28 27 34 33 29 28 27 25 31 35 34 33 36 30 28 32 38 4O 29 28 34 37 50% 3O.0 # 76 77 78 79 80~ 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 85% 33.2 SPEED 36 33 28 27 30 32 33 31 29 30 28 33 31 28 27 26 28 25 28 29 31 32 37 36 90% 35.0 BA YME TRICS RADAR TRAFFIC RESOURCES SPEED SURVEY PROJECT NAME: CITYWlDE SPEED LIMIT STUDY LOCATION: EMBARCADERO WEST OF BRET HARTE SITE ID: E2 CITY: PALO ALTO DATE:10/15/97 TIME:9AM- 11 AM DIRECTION: EASTBOUND FI1,E:3E2AM # 1 2 3 4 5 -6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 SPEED 33 31 30 25 29 29 33 34 32 29 28 30 28 34 31 28 27 29 30 26 28 33 32 29 27 PERCENTILE: SPEEDS: # 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 10% 25.0 SPEED 34 32 22 29 28 30 30 32 29 26 24 22 29 30 32. 25 25 28 29 33 34 29 26 30 32 15% 26.0 # 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 25% 27.0 SPEED 29- 25 34 41 35 29 26 33 37 35 36 33 29 28 3O 32 34 35 33 36 35 29 28 27 50% 29.0 # 76 77 78 79 80 81 82 83 84 85 86 87 88. 89 90 91 92 93 94 95 96 97 98 99 100 85% 33.2 SPEED 26 30 32 26 22 28 25 27 26 22 30 32 29 28 28 27 26 25 25 24 26 29 31 32 28 90% 34.0 BA YME TRICS R’AD AR TR.AFFIC RESOURCES SPEED SURVEY PROJECT NAME: CITYWIDE SPEED LIMIT STUDY DATE:1-0/15/97 LOCATION: EMBARCADERO WEST OF BRET HARTE TIME:9 AM - 11 AM SITE ID: E2 DIRECTION: WESTBOUND CITY: PALO ALTO FILE:3E2AM # 1- 2 3 4 5 6 7 8 9- lO 11. 12 13 14 __ 15 16 17 18 19 20 21 22 23 24 25 SPEED 29 28 33 32 25 25 26 26 36 35 35 40 29 28 33 32 26 29 30 32 28 26 27 35 34 PERCENTILE: SPEEDS: # 26 27 28 29 3O 31 32 33 34 35 36 37 38 39 4O 41 42 43 44 45 46 47 48 49 5O 10% 26.0 SPEED 32 22 32 36 32 31 37 29 28 3O 32 26 3O 33 29 27 26- 3O 32 25 29 33 35 37 36 15% 27.0 I # 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 25% 2&O SPEED 30 30 32 32 29 26 34 32 35 33 29 28 31 32 28 29 30 29 28 32 26 28 33 36 50% , 30.0 # 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 85% 35.0 SPEED 30 29 28 27 30 33 35 34 35 32 29 28 30 31 32 34 28 28 29 33 34 41 25 26 33 90% 35.0 BA YME TRICS TRA FFIC RADAR SPEED S RESOURCES URVEY PROJECT NAME: CITYWIDE S}:/’rT~D LIM!T STUDY LOCATION: EMBARCADERO EAST OF PRIMROSE SITE ID: E3 CITY: PALO ALTO DATE:10/15/97 TIME:9AM- 11 AM DIRECTION: EASTBOUND FILE:3E3AM # 1 2 3 4 5 6 7 8 9 10 11 12 43 14 15 16 17 18 19 20 21 22 23 24 25 SPEED 32 29 33 34 32 29 30 40 42 35 38 33 36 36 32 32 29 30 33 34 31 29 28 33 36 PERCENTILE: SPEEDS: # 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 # 26 27 28 29 30 3I 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 10% 28.0 SPEED 30 32 29 28 33 35 36 33 33 29 28 30 24 42 35 36 31 32 29 31 33 33 36 29 31 15% 28.0- 25% 29.0 SPEED 34 32 36 30 32 29 28 33 32 26 28 -32 28 24 26 28 39 33 36 34 26 5O% 3ZO # 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 lO0 85% 35.0 SPEED 29 28 27 30 33 31 29 28 32 32 26 28 30 32 31 29 28 27- 33 36 35 34 29 33 32 90% 36.0 BA YME TRICS RADAR TRAFFIC RESOURCES SPEED SURVEY PROJECT NAME: CITYWlDE SPEED LIMIT STUDY LOCATION: EMBARCADERO EAST OF PRIMROSE SITE ID: E3 CITY: PALO ALTO DATE: . 10/15/97 TIME:9AM- 11 AM DIRECTION: WESTBOUND FILE:3E3AM # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 SPEED 29 33 36 34 28 22 26 41 28 33 35 34 33 30 29 37 36 32 35 33 32 40 29 28 33 PERCENTILE: SPEEDS: # 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 -49 50 10% 28.0 SPEED 34 29 34 33 31 32 30 29 42 33 30 29 35 29 33 41 35 38 33 36 37 32 38 37 37 15% 29.0 # 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 25% 30.0 SPEED 35 34 32 29 28 33 31 32 42 33 35 36 37 40 32 35 33 36 38 33 39 -42- 31 32 28 50% 33.0 # 76 77 78 79 80 81 82 83 84 85 86 87 88 89 9O 91 92 93 94 95 96 97 98 99 100 85% 37.0 SPEED 29 3O 33 32 29 27 28 30 29 36 38 33 34 35 37 33 28 ~0% 38.O Final Report: MIDDLEFIELD ROAD SPEED ZONE ANA:LYSIS Prepared for: City of Palo Alto Prepared by: Fehr & Peers Assodates, Inc TransportalJon Consul~nts December 1997 971-1095 II. III. TABLE OF CONTENTS EXECUTIVE SUMMARY --1 Summary of Results .................................................1 Recommendations -1 GENERAL INFORMATION ................~ .........................6 ENGINEERING & TRAFFIC SURVEYS ...............................8 Prevailing Speeds ....................................................8 Roadway Conditions .................................................9 Accident History ..................................................10 Recommendation ..........................- ........................12 ]Figures _ _ 1 Middlefield Road Corridor ...........................................2 Tables 1 2 3 Roadway Conditions and Accident Rate Information .......................3 Recommended Speed Limits ..........................................4 ---Prevailing Speed Data -8 Two Year Average Accident Rates ....................................11 Appendix Appendix A - Radar Speed Data Engineering and Tro~: S’ur~ey Report for Middlefield Road between Menlo Park Cio~ Limit and San Antonio Road December 1997. EXECUTIVE SUMMARY Fehr & Peers Associates, Inc. was retained by the City of Palo Alto to conduct a speed zone analysis for a 4.2 mile section of Middlefield Road between the Menlo Park City Limit and San Antonio Road. The intent of this study was to conduct an engineering and traffic survey consistent with the California Vehicle Code (CVC) and CalTrans guidelines for consideration by the City Council to post speed limits which could be enforced by using radar. The study section was divided into six subsections for this speed survey.- The study corridor and corresponding subsections are illustrated in Figure I... : "Summary of Results Speed survey data was collected in each subsection to determine the 85~ percentile speeds. The 85t~ percentile speeds ranged from 32 to 37 miles perhour (mph). Based exclusively on the 85t~ percentile speeds, the recommended speed limits would be 30 mph from the Menlo Park City Limit to Loma Verde Avenue and 35 mph from Loma Verde Avenue to San Antonio Road. The CalTrans guidelines for conducting engineering and traffic surveys allow for an additional reduction of 5 mph to the speed limit based on accident history and non-apparent roadway conditions. An engineering review of the corridor characteristics and accident data (summarized in Table 1) found that such further reductions to the speed limit were not warranted. Recommendations An engineering study of the accident data and non-apparent roadway Conditions were considered in conjunction with the measured 85t~ percentile speed and the median speed of the 10-mph pace to determine the speed limit most appropriate for the safe and orderly flow of traffic on Middlefield Road. The recommended speed limits and primary supporting information are presented in Table 2. Fehr & Peers Associates City of Palo Alto Speed Zones December 1997 Corridor Segments: M-1 - Menlo Park City Limit to Channing Avenue M-2 - Channing Avenue to Oregon Expressway M-3 - Oregon Expressway to Towle Way M-4 - Towle Way to Loma Verde Avenue M~5 - Loma Verde.Avenue to Charleston Road M-6 - Charleston Road to San Antonio Road Figure 1 © Not to Scale MENLO PARK CITY LIMIT TO SAN ANTONIO ROAD Fehr & Peers Associates Engineering and Traffic Survey Report for Middlefield Road between Menlo Park City Limit and San Antonio Road December 1997 " m’0 00 ~0 ~ o ~Z ;~ Z Z ;~ ;~ Fehr & Peers Associates 3 Engineering and Traffic Survey R~port for Middlefield Road between Menlo Park CiO~ Limit and San Antonio Road December 1997 " Table 2 Recommended Speed Limits Middlefield Road Middlefield Road Segment Menlo Park City Limit to Channing Avenue Channing Avenue to Oregon Expressway Oregon Expressway to,Towle Way Towle Way to Loma Verde Avenue Loma Verde Avenue to Charleston Road Existing Speed Limit 25 25 25 25 85th Percentile Speed 32 33 33 34 36 Speed Limit based on 85th Percentile Speedt 30 ~ 30 30 30 35 Accident Rate/ Roadway Conditions information~- Above/No Above/No Above/No Below/No Below/No Median Speed of 10-mph Pace~ 28 30 29 29 33 Recommended Speed Limit 30 30 30 35 Charleston Road to 25 37 35 Above/No 33 35San Antonio Road I. CalTrans guidelines require setting radar-enforceable speed limits at the 5 mph interval immediately below the 85’h percentile speed, unless accidents and/or non-apparent roadway conditions warrant further lowering. 2. See Table 1 for Accident Rate and Roadway Conditions Information 3. ITE emphasizes that the speed limit should not be set below the median speed of the 10-mph pace. These recommended speed limits are higher than the existing 25 mph posted speed limit. The results of the speed surveys and evaluation of roadway conditions and the accident history indicate that, to permit radar-enforcement, the speed limit should be raised to 30 mph north of Loma Verde Avenue and 35 mph south of Loma Verde Avenue. Fehr & Peers Associates 4 Engineering and Traffic Survey Report for Middlefield Road between Menlo Park City Limit and San Antonio Road December 1997 There are five school zones located along the Middlefield corridor. "l~nree school zones are between Channing Avenue and Oregon Expressway, the fourth school zone is between Mayview Road and Charleston Road, and the fifth is between Charleston and San Antonio. The school zones are clearly marked and signed with 25 mph school speed zone signs. During school commuter periods (when children are present), radar may be used to enforce speeds within the school zones. Fehr & Peers Associates 5 . - II. Engineering and Traffic Survey Report for MiddlefieM Road between Menlo Park City Limit and San Antonio Road December 1997 GENERAL INFORMATION This report conforms with the conditions of Section 627 - "Engineering and Traffic Survey" of the CVC which states that the following factors shall be included for consideration: (1)Prevailing speeds as determined by traffic engineering measurements. (2)Accident records. (3)Highway, traffic, and roadside conditions not readily apparent to the driver. The method for conducting engineering and traffic surveys for City ..and County arterials, .collectors, and local roads as described in the CalTrans Traffic Manual states that the speed limit should normally be established at the first five mile per hour increment below the 85th percentile speed. The 85~ percentile speed is the speed at or below which 85 percent of the motorists are driving. Speed limits higher than the 85~ percentile speed are not generally considered reasonable or safe, and speed limits set too far below the 85th percentile speed do not facilitate the orderly movement of traffic. Speed limits established on this basis conform to the consensus of those who drive highways as to what speed is reasonable and safe, and are not dependent on the judgement of one or a few individuals. However, an engineering analysis of the accident history and roadway conditions may also indicate the need for a further five mph reduction in the speed limit indicated by the 85’h percentile speed. Such a reduction could be based on one or more of the following factors: Most recent two year accident record Roadway conditions not readily apparent to drivers ao Roadway design speed Safe stopping sight distance Superelevation Shoulder conditions Profile conditions Intersection spacing and offsets Fehr & Peers Associates 6 Engineering and Traffic Survey Report for Middlefield Road between Menlo Park City Limit and San Antonio Road December 1997 - g.Driveway characteristics h.Pedestrian traffic i.Sidewalks The measurement of prevailing speeds was done by certified technician using a calibrated radar speed gun. The following procedures were followed for the measurements: ,.o Locations were selected where prevailing speeds were representative of the entire speed zone.- Areas near traffic control devices and horizontal and vertical curves were avoided. ¯Speed measurements were taken during off-peak hours on weekdays. ¯Weather was fair and the surveyor and radar equipment were inconspicuous. ¯Angle to roadway centerline was no greater than 15 degrees in both directions. ¯The minimum survey sample was 100 vehicles in each direction. Fehr & Peers Associates 7 III, Engineering and Traffic Survey Report for Middlefield Road between Menlo Park City Limit and San Antonio Road December 1997 ENGINEERING AND TRAFFIC SURVEYS The engineering and traffic surveys on Middlefield Road were conducted in accordance with Section 627 of the CVC and the CaITrans Traffic Manual. This survey includes the prevailing speeds, accident rates, roadway conditions not readily apparent to the driver, and recommendations. Prevailing Speeds The prevailing speed data consists of the 85t~ percentile speeds, the 10-mph pace, and the median .speed of the 10-mph pace. The prevailing speed data is presented in Table 3. Other factors pertaining to the prevailing speeds along the corridor are: The existing speed limit is 25 mph. Speed surveys were conducted on October 15~, 1997, between 9:00 and 11:00 a.m. except for the fh’st subsection where the radar data was collected from 11:00 a.m. to 12:00 p.m. and from 1:00 to 2:00 p.m. (Refer to radar speed data in Appendix A). Table 3 Prevailing Speed Data Middlefield Road Segment Menlo Park City Limit to Channing Avenue Channing Avenue .to Oregon Expressway Oregon Expressway to Towle Way Towle Way to Loma Verde Avenue Loma Verde Avenue to Charleston Road Charleston Road to San Antonio ROad 85’h Percentile Speed, -- (mph) NB SB 32 33 33 34 , 33 34 34 34 36 36 37 36 Pace Speed (mph) Median of the Pace Speed (mph) NB SB 28 30 30 30 29 30 29 30 33 33 33 33 NB SB 24-33 26-35 26-35 26-35 25-34 26-35 26-35 26-35 28-37 28-37 27-36 27-36 Fehr & Peers Associates 8 Engineering and Traffic Survey Report for Middlefield Road between Menlo Park City Limit and San Antonio Road December 1997 - In all of the subsections on Middlefield Road, the 85t~ percentile speed is higher than the posted speed limit. Based exclusively on the 85th percentile speeds, the indicated speed iimit would be 30 mph from the Menlo Park City Limit to Loma Verde Avenue and 35 mph from Loma Verde Avenue to San Antonio Road. CalTrans guidelines allow that a review of the non-apparent roadway conditions and accident history may justify reducing the radar enforceable speed by additional 5 mph below the 30 and 35 mph speed limits dictated_by the 85th percentile speed. Table 3 also illustrates the 10-mph pace and the median of the 10-mph pace along Middlefield Road. The 10-mph pac_e is the 10-mph .increment of speed containing the largest number of vehicles. The Institute of Transportation Engineers advises against setting a speed limit below the median speed of the 10-mph pace, and research from the Transportation ResearchBoard indicates that setting the speed limit too far below the 85t~ percentile-speed generally results in an increase in the number of accidents. Roadway Conditions Fehr & Peers Associates conducted field reconnaissance to identify the physical characteristics and land uses on Middlefield Road that may not be readily apparent to the driver. Information pertaining to pavement geometry and alignment, land uses, driveway densities, bicycle and pedestrian activity, and other factors were collected. Middi~eld Road is mostly a four lane, undivided roadway from the Menlo Park City Limit to San Antonio Road except between Channing Avenue and Oregon Expressway. In this section, Middlefield Road has a two lane cross-section. Parking is restricted in various sections throughout the corridor. Separate bike lanes are provided but are not contiguous from subsection to subsection. The surrounding land use is primarily residential with some commercial blocks toward the southern end of the corridor. In the residential subsections, mature trees planted near the edge of pavement create a canopy effect over the roadway. The pavement is in fair condition Fehr & Peers Associates -9 Engineering and Traj~c Survey Report for MiddlefieM Road between Menlo Park City Limit and San Antonio Road December 1997 and none of the observed roadway conditions warrant a further five mph reduction to the speed limit indicated by the 85~h percentile speed. School zone speed limits are posted to protect children in school areas. There are five school zones located along the Middlefield corridor. -Three school zones are between Channing Avenue and Oregon Expressway, the fourth school zone is between Mayview Road and Charleston Road, and the fifth is between Charleston and San Antonio. The State of California’s statute for school zone speed limits is 25 mph. Although, the recommended radar-enforceable speed limits are higher than 25 mph throughout the corridor, the 25 mph school zone speed limit could be enforced using radar within the school zone when children are present. Accident History The CaITrans Traffic Manud recommends that the most recent two-year accident history be used ¯ to calculate accident rates for determining radar-enforceable speed limits. For this engineeringand traffic survey, the most recent two-year rates (1995 and 1996) were used as the primary basis of determining the safety level of the street and setting the speed limits. Accident data from 1995 through 1996 was collected from the City of Palo Alto Police Department and summarized tO determine the two-year accident rates of each subsection. The accident rate is based on one million-vehicle-miles of travel and is an indicator of high accident locations. High accident locations are areas where the accident rate is higher than the average for other similar locations or conditions. Accidents not reported to the Palo Alto Police Department were not included. The accident rate for segments of roadway can be calculated by the equation: Accident Rate = (# of accidents x 1 million) / (total vehicle miles of travel) Typical four i~e, urban roads in the Bay Area (CalTrans District 4) have an average accident rate of 3.97 per million-vehicle-miles traveled. The average accident rate for typical two lane urban Fehr & Peers Associates I0 Engineering and Traffic Survgy Report for Middlefield Road between Menlo Park City Limit and San Antonio Road ~ December 1997 roads in the Bay Area (CalTrans District 4) is 1.93 per million-vehicle-miles traveled. The CalTrans District 4 accident rates for four and two lane, urban roadways were determined from CalTrans 1995 Accident Data on California State Highways. The calculated two-year average accident rates for each segment of the corridor are presented in Table 4. Table 4 - Two-Year Average Accident Rates Middlefield Road (1995 through 1996) Middlefield Road Segment Menlo Park City Limit to Channing Avenue Channing Avenue to Oregon Expressway Oregon Expressway to Towle Way Towle Way to Loma Verde Avenue Loma Verde Avenue to Charleston Road Charleston Road to San Antonio Road Number of Accidents 66 45 38 9 33 32 Average Daily Traffic 19,800 17,400 , 17,800 15,500 15,000 15,600 2-Year Average Accident Rate 6.09 ~2.73 5.73 3.62 3.17 6.24 Three of the four-lane subsections exceed the Bay Area (CalTrans_District 4) average 3.97 accident rate. In addition, the two lane subsection between Channing Avenue to Oregon Expressway exceeds the 1.93 Bay Area average rate. This indicates that the speed limit in these four subsections could be reduced by an additional 5 mph. However, CalTrans guidelines emphasize that establishing a speed limit by more than 5 mph below the 85th percentile speed should be done with great care to prevent setting the speed limit which is below that traveled by the majority of drivers and making violators of a disproportionate number. Furthermore, research from the Transportation Research Board indicates that setting the speed limit too far below the 85th percentile speedgenerally results in an increase in the number of accidents, and the Institute of Transportation Engineers advises against setting the speed limit below the median speed of the 10- mph pace.- Fehr & Peers Associates 11 Engineering and Traffic Survey Report for Middlefield Road between Menlo Park City Limit and San Antonio Road December 1997 To determine whether any subsections should be reduced by an additional 5 mph due to the accident history, a review was made to see if the reduced speed limit would be below the median speed of the 10-mph pace. In the subsection from the Menlo Park City Limit to Channing Avenue, the accident rate (6.09) exceeds the Bay Area CalTrans average by more than 50%. A speed limit reduction by an additional 5 mph was considered to lower the speed limit to 25 mph. However, the median speed of the 10-mph pace in this subsection was 28 mph, and reducing the speed limit below this speed would make violators of a disproportionate number of drivers (over 90%). Therefore, the speed limit could not be reduced to 25 mph. This also applied to the subsections from Oregon Expressway to Towle Way and from Charleston Road to San Antonio Road, which .also exceeded the Bay Area average accident rates for four lane roadways. The median speed of the 10 mph pace was 29 mph from Oregon Expressway to Towle Way and 33 mph from Charleston Road to San Antonio Road. Reducing the speed limit to 25 mph between Oregon and Towle or to 30 mph between Charleston and San Antonio would result in a disproportionate number of drivers exceeding the speed limit. Finally, the two lane subsection from Channing Avene to Oregon Expressway also exceeded the average accident rate of 1.97. In this subsection, the median of the 10-mph pace was 30 mph. By reducing the speed limit to 25 mph in this subsec.tion, the radar data indicates a disproportionate share of drivers would exceed the speed limit. Recommendation Based on review and analysis of speed survey data, roadway conditions and accident history on Middlefield Road, a speed limit of 30 mph from the Menlo Park City Limit to Loma Verde Avenue and a speed limit of 35 mph from-Loma Verde Avenue to San Antonio Road are justified and so recommended as the radar enforceable speed limits. Fehr & Peers Associates 12 APPENDIX A MIDDLEFIELD ROAD RADAR SPEED DATA BA YMETRICS TRAFFIC RESOURCES RADAR SPEED SURVEY PROJECT NAME: CITYWIDE SPEED LIMIT STUDY DATE:1-0/15/97 LOCATION: MIDDLEFIELD ROAD NORTH OF EVERETT SITE ID: M1 TIME:IlAM- 12NN/IPM- 2P DIRECTION: NORTFIBOUND CITY: PALO ALTO FILE:3M1PM 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 SPEED 26 29 34 32 25 33 34 32 29 30 36 28 24 25 27 30 30 32 26 28 32 31 28 35 PERCENTILE: SPEEDS: I # 26 27 28 29 30 31 32 33 34 35 36 37 38 39 4O 41 42 43 44 45 46 47 48 49 50 10% 24.9 SPEED 34 3O 32 26 22 24 28, 22 29 25 3O 32 34 26 25 20 24 27 31 32 35 15% 2~0 # 51 52 53 54-- 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 25% 26.0 SPEED 33 29 30 35 30 28 28 26 29 34 32 33 29 34 32 27 26 30 25 24 28 31 22 25 27 50% 28.0 # 76 77 78 ¯-79 8O 81 82 83 84 85 86 87 88 89 9O 91 92 93 94 95 96 97 98 ¯99 100 85% 32.0 SPEED 28 29 32 25 30 32 26 24 27 28 30 26 25 28 27 25 30 26 28 31 25 24 27 29 90% 33.1 BA YMETRICS TRAFFIC RESOURCES RADAR SPEED SURVEY PROJECT NAME: CITYWIDE SPEED LIMIT STUDY LOCATION: MIDDLEFIELD ROAD NORTH OF EVERETT SITE ID: M1 CITY: PALO ALTO DATE:10/15197 ![ TIME:11 AM - 12NN / 1PM - 2P DIRECTION: SOUTHBOUND FILE:3MIPM # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 SPEED # 28 33 27 30 32 33 26 30 34 25 32 31 29 26 30 31 28 30 26 33 27 32 29 26 27 PERCENTILE: SPEEDS: #! SPEED 26 27 28 29 30 31 32 33 34 35 36 37 38 SPEED SPEED 28 33 26 - 34 76 77 78 79 80 81 82 83 84 39 40 41 42 43 44 45 46 47 48 49 50 10% 26.0 30 32 35 33 27 30 32 24 28 29 33 31 32 28 32 35 28 27 25 32 29 28 27 33 34 15% 27.0 51 52 53~ 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 25% 28.0 29 35 33 29 30 27 28 31 32 29 34 26 33 28 27 25 29 30 30 32 29 24 35 31 29 50% 30.0 85 87 88 89 90 91 92 93 94 95 96 97 98 99 100 85% 33.0 32 30 28 29 32 27 26 35 33 31 27 28 32 25 30 28 27 34 33 29 36 90% 34.0 BA YMETRICS TRAFFIC RESOURCES RADAR SPEED SURVEY PROJECT NAME: CiTYWIDE SPEED LEv[IT STUDY LOCATION: MIDDLEFIELD ROAD NORTH OF SEALE SITE ID: M2 CITY: PALO ALTO DATE:10/15/97 TIM~:9AM- 11 AM DIRECTION: NORTHBOUND FILE:3M2AM # 1 2 3 4 5 6 7 8 9 10 11 12 13, 14 15 16 17 ,18 19 20 21 22 23 24 25 SPEED 28 32 33 27 26 30 35 28 27 25 29 24 28 27 30 32 26 32 32 29 28 33 34 PERCENTILE: SPEEDS: # 26 27 28 29 30 31 32 33 34- 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 26.0 SPEED 27 35 34 32 30 35 31 33 34 33 30 15% 27.0 - ! # 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 25% 1 28.0 SPEED 2-7-~ 32 28 33 29 32 26 28 27 30 30 32 33 34 29, 35 33 36 31 28 3O 27 32 32 ,33 50% 3~0 # 76 77 78 79 80 81 83 84 85 SPEED 27 26 30 32 28 29- 32 28 27 26 30 32 33 28 27 26 32 33 31 32 28 ~-- 29 90% 33.1 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 8.5% 33.0 i BA YMETRICS TRAFFIC RESOURCES RADAR, SPEED SURVEY PROJECT NAME: CITYWIDE SPEED LIM/T STUDY DATE:10/15/97 ...... LOCATION: MIDDLEFIELD ROAD NORTH OF SEALE TIME:9 AM - l l AM SITE 1:!3:M2 DIRECTION: SOUTHBOUND CITY: PALO ALTO FILE:3M2AM # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 SPEED 28 30 29 32 33 32 34 34 33 31 30 28 35 # 26 27 28 29 30 31 32 33 34 35 36 37 38 SPEED 34 27 28 27 30 32 28 29 34 32 27 26 33 # 51 52 53 54 55 56 57 58 59 60 61 62 63 SPEED 36 3O 32 3O 26 28 33 28 28 27 34 33 35 29 30 26 28 33 39 40 41 42 43 44 45 46 47 48 49 50 # 76 77 78 79 80 81 82 83 84 85 86 87 88 SPEED 34 33 29 38 27 32 28 32 33 35 33 35 28 25 29 32 - 31 30 27 29 29 32 33 24 64 65 66 67 68 69, 70 71 72 73 74 75 29 35 35 34 33 -30- 32 ---30 28 PERCENTILE:50%25% 28.0 15% 28.0 10% 27.0 91 92 93 94 95 96 97 98 99 100 85% 34.0SPEEDS:30.5 27 38 36 32 29 90% 34.1 II i BA YME TRICS TRA FFIC RADAR SPEED S RESOURCES URVE-Y PROJECT NAME: CITYW’IDE SPEED LIMIT STUDY DATE:10/15/97 LOCATION: MIDDLEFIELD ROAD NORTH OF SUTTER,TIME:9 AM - 11 AM SITE ID: M3 ~-DIRECTION: NORTHBOUND CITY: PALO ALTO FILE:3M3AM # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 I7 18 19 20 21 22 23 24 25 SPEED 30 29 28 31 32 26 27 28 33 34 28 29 28 26 29 33 ....32 30 30 28 27 26 34 32 31 # 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 ’44 45 46 47 48 49 5O 10% 26.0 PERCENTILE: SPEEDS: SPEED 33 28 32 35 30 28 26 29 29 30 28 27 32 33 32 28 27 30 31 32 26 28 3O 25 27 15% 2&O # 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 2.~% 27.0- SPEED 29 33 34 27 26 28 30 32 34 37 26 33 22 2fi 29 30 32 35 34 26 28 29 29 50% 29.0 # 76 77 78 79 8O 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 33.0 SPEED 31 -- 32 28 3O 28 22 25 27 34 33 35 3O 29 26 28 27 33 26 29 34 3O 90% 34.0 BA YMETRICS TRAFFIC RESOURCES. RADAR SPEED SU-RVEY PROJECT NAME: ClTYWIDE SPEED LIMIT STUDY LOCATION: MIDDLEFIELD ROAD NORTH OF SUTTER SITE ID: M3 CITY: PALO ALTO DATE:10/15/97 TIME:9AM- 11 AM DIRECTION: SOUTHBOUND FILE:3M3AM #SPEED 1 32 2 33 3 28 4 27 5 26 6 34 7 26 8 29 9 31 10 30 11 28 12 27 13 29 14 22 15 28 16 34 17 ....32 18 35 19 29 20 31 .21 28 22 27 23 29 24 1 30 25 I 28 PERCENTILE: SPEEDS: # 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 lO% 27.0 SPEED 28 ~29 34 32 29 33 26 32 35 33 28 30 31 33 32 34 29 28 30 35 33 27 29 29 33 15% 27.0 # 51 52 53 54 55 56 57 58 59 6O 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 2..$% 28.0- SPEED 31 28 33 27 29 34 28 32 30 2s 26 39 34 28_ 29 34 32 28 27 35 39 32 28 27 35 50% 30.0 # 76 77 78 79 8O 81 82 83 84 85 86 87 88 89 9O 91 92 93 94 95 96 97 98 99 100 85% 34.0 SPEED 33 28 27 33 34 34 31 26 28 30 28 27 29 30 32 33 35 31 28 27 26 34 33 29 28 90% 34.0 BAY METRICS RADA-R TRAFFIC RESO-URCES SPEED SURVEY PROJECT NAME: CITYWIDE SPEED LIMIT STUDY LOCATION: MIDDLEFIELD ROAD NORTH OF LAYNE SITE ID: M4 CITY: PALO ALTO # 1 2 3 4 5 6 7 8 9 10- 1! 12 13 14 15 16 17 18 19 2O 21 22 23 24 25 DATE:10/15/97 TIME:9 AM - 11 AM D[R.ECTION: NORTHBOUND FILE:3M4AM SPEED 29 26 30 35 28 28 29 27 30 35 25 29 28 27 33 28 36 30 35 33 29 28, 27 34 35 # 26 27 28 2-9 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 5O SPEED 30 30 29 28 33 28 30 30 31 -28 28 27 34 33 29 28 27 34 35 26 38 30 34 34 # 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 SPEED 32. 28 27 29. 27 32 28 25, 29 30 29 26 35 28 33 30 28 29 35 27 28 27 26 28 29 # 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ,,PERCENTILE:10%15%25%50%85% ....SPEEDS:26.0 27.0 27.8 29.0 ~ 34.2 BA YMETRICS TRAFFIC RESOURCES RADAR SPEED SUR-VEY PROJECT NAME: CITYWIDE SPEED LIMIT STUDY LOCATION: MII)DLEFIELD ROAD NORTH OF LAYNE SITE 13): M4 CITY: PALO ALTO DATE:10/15/97 TIME:9AM- 11 AM DIRECTION: SOUTHBOUND FILE:,3M4AM # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 ’ SPEED i 3o 29 32 31 34 3g 30 31 34 34 PER CEN TIL E: SPEEDS: # 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 5O 10% 27.0 SPEEb 33 36 28 29 29 3O 33 28 27 26 32 35 28 29 27 26, 28 26 37 26 15% 28.0 [ # 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68- 69 70 71 72 73 74 75 25% 28.0 SPEED 29 34 32 35 33 29 30 30 32 32 28 31 32 27 29 30 34 33 28 28 27 29 29 30.5 # 76 77 78 79 80 81 82 83 84 85 86- 87 88 89 90 91 92 93 94 95 96 97 98 99 100 85% 34.0 SPEED 31 31 30 32 35 36 33 32 28 27 26 28 3O 26 28 29 33__ 34 26 28 3O 30 32 33 28 90% 35.0 BA YME TRICS TRA FFIC RADAR SPEED S RESOURCES URVEY PROJECT NAME: CITYWIDE SPEED LIMIT STUDY LOCATION: MIDDLEFIELD ROAD NORTHOF ASHTON SITE ID: M5 CITY: PALO ALTO ,, DATE:10/15197 TIME:9AM- 11 AM DIKECTION: NORTHBOUND FILE:3M5AM # 1 2 3 4 5 6- 7 8 9 10 11 12 13 14 15 16 17 18 19 2O 21 22 23 24 25 SPEED 29 28 34 33 35 30 31 35 35 29 28 30 33 33 34 35 33 37 28 29 26 28 34 31 PERCENTILE: # 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 5O SPEEDS: 10% 28.0 SPEED 33 35 33 34 33 29 28 32 35 37 33 39 34 34 33 29 28 30 32 35 33 32 31 33 38 15% 29.0 .# 51 52 53 54 55 56 57 58 -59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 25% 30.0 SPEED 42 29 33- 35 28 34 32 37 35 33 39 38 34 35 37 36 33 40 29 31 32 35 35 37 37 50% 33.0 #i SPEED 76 i 30 77 1 33 78 29 79 i 28 80 32 81 33 82 I 29 83 30 84 31 85 ~31 86 36 87 " 34 88 ~ ~ 32 89 I 28 90 ;27 91 ~29 92 [ 33 93 l 29 94 [34 I 95 I 35 96 37 97 36 98 34I 99 40 100 42 85%90% 36.2 37.0 BA YME TRICS RADA,R TRA FFIC RESO UR.CES SPEED-SURVEY PROJECT NAME! CITYWIDE SPEED LIMIT STUDY LOCATION: MIDDLEFIELD ROAD NORTH OF ASHTON SITE if): M5 CITY: PALO ALTO DATE:10/15/97 TIME:9 AM - 11 Alvl DIRECTION: SOUTHBOIJ’ND FILE:3M5AM # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 SPEED [34 33 32 I 2S 29 34 32 4O 32 33 35 33 38 33 i 35 PERCENTILE: # 26 27 29 3O 31 32 33 34 35 36 37 38 39 4O 41 43 44 45 46 47 48 49 5O 10% 28.0 SPEED 30 -32 33 33 34 33 35 32 36 3O 35 32 33 34 34 32 35 37 33 28 29 35 35 26 28 15% 28.0 # 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 25% 29.8 SPEED 32 38 33 39 41 35 40 35 37 42 46 38 33 37 35 29 28 29 31 32 33 28 27 29 50% 33.0 I # 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 85%. 36.0 SPEED 29 30 30 33 32 31 32 34 32 35 29 28 30 ¯30 33 31 29 28 22 28 27 26 25 28 34 90% 37.1SPEEDS: BA YME TRICS RADAR TRAFFIC RESOURCES SPEED SURVEY PROJECT NAME: CITYWIDE SPEED LIMIT STUDY DATE: 10/15/97 ,i LOCATION: MIDDLEFIELD RD. NORTH OF MONTROSE TIME:9 AM - 11 AM SITE ID: M6 DIRECTION: NORTHBOtYND CITY: PALO ALTO FILE:3M6AM # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 SPEED 35 29 30 33 34 28 35 35 36 37 40 42 33 35 37 35 36 33 31 32 28 28 35 38 38 PERCENTILE: SPEEDS: I # 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 ~47 48 49 5O 10% 28.0 SPEED 33 29 28 27 35 36 33 35 34 28 29 35 35 36 34 41 42 30 35 38 42 42 46 43 38 15% 28.0 # 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 25% 29.0 SPEED 37 33 ¯35 34 40 29 40 28 34 ~9 34 30 ~0% 4.o # 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 85% 37.2 SPEED 35 35 !34 t 36 32 29 28 34 33 35 29 ~28 ~27 32 ~28 ~27 !29 34 ~ 32 9O% 40.0 BA YMETRICS TRAFFIC RESOURCES RADAR SPEED SURVEY PROJECT NAME: CITYWIDE SPEED LIMIT STUDY LOCATION: MIDDLEFIELD RD. NORTH OF MONTROSE SITE ID: M6 CITY: PALO ALTO DATE:, 10/15/97 TI2VIE:9AM- 11 AM DIRECTION: SOUTHBOUND FILE:3M6AM # 1 2 3 4 5 6 7 8 9 lO 11 12 13 14 15 16 17 18 19 2o 21 22 23 24 25 SPEED 33 29 28 34 33 35 35 36 30 28 34 33 I 35 36 37 33 28 34 33 36 35 33. 34 28 27 PERCENTILE: SPEEDS: # 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 lO% 28.0 SPEED 23 30 35 42 38 36 33 35 34 24 28 33 39 29 33 36 32 28 27 32 33 35 37 40 40 15% 2&O # 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 25% 29.0 SPEED 35 36 35 38 42 33 36 38 42 35 33 29 29 30 32 28 34 28 38 35 37 33 36 35 34 50% 33. 0 # 76 " 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 85% 36.0 SPEED 33 J 30 35 29 28 30 28 27 29 31 32 32 29 32 28 27 29 33 34 28 27 29 ’ 30 32 ’33 9O% 37.1