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Home My WebLink About7.2 Silvergate Dr Traffic Study J CITY OF DUBLIN - g r� AGENDA STATEMENT City Council Meeting Date: September 22, 1986 SUBJECT: Silvergate Drive Traffic Study EXHIBITS ATTACHED: Preliminary report from TJKM; additional information will be presented at the meeting. RECOMMENDATION: 1) Receive Staff presentation. 2) Receive public input. 3) Determine if additional study is necessary. 4) Direct Staff to formulate recommendation for the meeting of October-_13, 1986. FINANCIAL STATEMENT: None at this time. DESCRIPTION: In response to requests from residents of Silvergate Drive, the City Council requested that TJKM, the City's Traffic Engineering Consultants, study traffic volume and speeds and crosswalk locations on Silvergate Drive once the street had been opened to through traffic. TJKM's preliminary report (attached) provides the following information: 1. Regarding installation of STOP signs on Silvergate at Peppertree Road, the minimum volume warrants are not met. There is also no sight distancerproblem at that intersection. 2. The speed survey is not complete at this time; however, additional data will be available by the time of the City Council meeting and will be presented orally. Speed surveys conducted previously indicate that the 85th percentile speed on Silvergate Drive is well above the posted 25 m.p.h. speed limit, and increased police enforcement of the speed limit has now been targeted with the City's new traffic unit. 3. The traffic volumes do not meet the warrants for an adult crossing guard at the intersection of Silvergate and Peppertree; however, the minimum volume warrant is 80 - 87% satisfied. There is an existing yellow crosswalk on Silvergate at Amarillo Road, where crossing is safer, and it is recommended that children be. instructed to cross there rather than at Peppertree. The crosswalk at Peppertree was removed for this reason. As more homes are built in this area, traffic volumes will increase and the warrant may be met for a crossing guard in the future. Additional data on numbers of school children will be presented at the meeting. This meeting will serve as a fact-finding study. The Council will hear from Staff and hopefully from the public. Notices have been sent to all residents fronting on Silvergate Drive. From the data Staff has gathered and that which the residents put forth, recommendations will be formulated for a report to the Council at the meeting of October 13, 1986. ---------------------------------------------------------------------------- ITEM NO. COPIES TO: TJKM r PLEASANTON SACRAMENTO FRESNO TRANSPORTATION CONSULTANTS CONCORD September 17, 1986 Mr. Lee Thompson - City Engineer City of Dublin 6500 Dublin Boulevard Dublin, CA 94568 Dear Lee: We have analyzed the existing traffic volumes and speeds on Silvergate Drive and Peppertree Road. We also analyzed the accident history and the sight restrictions at the intersection. We compared this data to the warrants for a four-way STOP sign installation in residential neighborhoods. Stop Sign Warrants The minimum volumes for four-way STOP sign installations are a total vehicular volume of 300 vehicles per hour (vph) entering the intersection from all four approaches; for any eight hours of an average day. In addition, one-third of the total volume must be attributable to the minor street. The total traffic volume at the intersection of Silvergate and Peppertree exceeds 300 vph for nine hours of the day. However, the side street traffic constitutes only 24 percent of the total traffic entering the intersection. Therefore, the minimum volume warrants for STOP sign installation are not met at this intersection. The accident history at this intersection for the past three years was reviewed. In 1984, there was one single vehicle accident. There were no accidents in 1985. In 1986, there has been one vehicle-bicycle collision. The 1986 accident involved a right turning southbound vehicle on Peppertree Road, and an eastbound bicyclist riding in the westbound bike lane on Silvergate Drive. This type of accident would not be correctable by four-way STOP signs. Therefore, the accident history does not justify four-way STOP sign installation. Collision diagrams of these two accidents are depicted in the attached Figure 1. The visibility at the intersection was analyzed. The sight distance is unrestricted for a southbound vehicle on Peppertree Road looking in either direction. Similarly, the sight distance is unrestricted for a northbound vehicle looking to the cast. However, to the west, a northbound vehicle on Peppertree has sight distance of approximately 250 feet while waiting at the marked limit line. If the vehicle pulls forward to the tangent to the curb, the sight distance increases to 4637 Chabot Drive, Suite 214/ Pleasanton, California 94566 • (415) 463-0611 Mr. Lee Thompson -2- September 17, 1986 approximately 300 feet. This is adequate sight distance for a vehicle to enter an intersection without requiring the cross traffic traveling at 25 mph to reduce speed. A summary of these warrants for four-way STOP sign installation are presented in the attached Figure 2. Speed Surveys According to-a speed survey conducted by JHK and Associates on December 11, 1984, the 85th percentile speed on Silvergate Drive is 37 mph between Silvertree Lane and San Sabana Road. TJKM also recently conducted a speed survey on Silvergate Drive north of Hansen Lane on September 3, -1986. The 85th percentile speed was 40 mph for northbound traffic and 44 mph for southbound traffic. It is apparent that the posted speed limit of 25 mph is not being observed. Therefore, increased enforcement is recommended to reduce excessive speeds. TJKM will conduct a speed survey on Silvergate near Peppertree Road on September 18 or 19, 1986. The results will be available at the City Council meeting on Monday September 22, 1986. Adult Crossing Guard Warrants The traffic volumes on Silvergate Drive were compared with the minimum volumes for adult crossing guard warrants. These warrants state that the vehicular traffic volume must exceed 350 vph in each of any two hours during which forty or more pedestrians are going to or from school. The highest traffic volume during the times in which school children are going to school (8:00 - 9:30 a.m. and 1:45 - 3:15 p.m.) are 306 vph and 280 vph, respectively. :Therefore; adult crossing.guard warrants are not met at this intersection. However, this minimum volume warrant is 80 - 87 percent satisfied. There is an existing yellow school crosswalk on Silvergate Drive at Amarillo Road. The white crosswalk on Silvergate at Peppertree Road was removed in order to encourage children to cross Silvergate Drive at Amarillo Road where there are fewer turning movements into the side street rather than at Peppertree Road. However, field observations revealed that many student pedestrians and bicyclists are still crossing at Peppertree Road. Seven pedestrians and one bicyclist were observed crossing Silvergate Drive on September 15, 1986 and eight pedestrians and eleven bicyclists were observed crossing Silvergate Drive on September 16, 1986 between approximately 1:45 and 2:30 p.m. It is recommended that all children on foot be instructed to cross Silvergate Drive at Amarillo Road. More children crossing at a single location will increase their visibility and will help to meet the minimum school pedestrian volumes of the adult crossing guard warrants. Also, motorists are currently warned of the presence of school children by the existing signing and pavement markings (SCHOOL XING) at Amarillo Road. However, the pavement markings reading "SLOW SCHOOL XING" are faded and are not visible. These should be repainted. TJKM intends to count the number of school age pedestrians crossing Silvergate Drive at both Amarillo Road and Peppertree Road to determine if the minimum volume of 40 pedestrians per hour would be met if all pedestrians crossed Silvergate Drive at a single location. ACC DATE IE LEGEND: r 7-19-8 16:20 A) RIGHT ANGLE ---�- LEFT TURN `-Q�- REAR-END - -�-- HEAD-ON SIDE SWIPE, REAR-ENE SIDE SWIPE, HEAD-ON PED eiKE PEDESTRIAN, BICYCLE --- �- BACKING (L) DAYLIGHT (D) DARKNESS O PROPERTY DAMAGE ❑ FIXED OBJECT ® INJURY • FATAL - 0> PARKED CAR OUT OF CONTROL -51L VERGATE DR. BIKE _ r . CITY OF LUBL IN W W - LOCATION W PEPPERTREE RD. A _ SILVERGATE DR PERIOD COVERED: l- 1-1984 to 8 -31-198G DATE COMPILED• 9-/�-/986 COLLISION DIAGRAM FOZI CD-2 J' FIGURE 2 - WARRANTS FOR FOUR-WAY STOP SIGN I14STALLATION - Four-way stop sign installation may be considered if any of the following conditions exist: 1. VOLUME (a) Total vehicular volume entering the intersection from all approaches must average 300 per hour for any 8 hours of an average day. (24-hour equivalent approximately 4,000 vehicles.) (b) In addition, the vehicular volume entering the intersection from the minor street or streets for the same 8 hours must average at least 1/3 of the total volume entering the inter- section (100 per hour min.) . 2. ACCIDENTS - Five ore more of types susceptible of correction by stop signs within a 12-month period, with satisfactory observance and en- forcement of less restrictive control. 3. VISIBILITY The straight line sight distance on one or more approaches of the major street for vehicles or pedestrians crossing the inter- section is less than 160 feet. 4. RESIDEN'T'IAL AREA Volume warrants to be reduced to 600 of the values above if ALL of the following conditions are met: (a) Both streets have residential frontage with existing 25 mph speed limits. . (b) Neither street is an adopted through street. (c) Neither street exceeds 40 feet of roadway width. (d) No existing stop sign or signal is located on the more heavily traveled street within a distance of 800 feet. (e) Intersection has four. legs, with streets extending 800 feet or more away from the intersection on at least three sides. (f) Installation of a four-way stop is compatable with overall traffic circulation needs for the residential area. 9