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HomeMy WebLinkAboutItem 7.2 TrafCirculatnEval DHS CITY CLERK File #590-40 AGENDA STATEMENT CITY COUNCIL MEETING DATE: July 16, 2002 SUBJECT: Evaluation of Traffic Circulation and Safety in the Vicinity of Dublin High School Report Prepared by: Lee Thompson, Public Works Director ATTACHMENTS: Traffic Report RECOMMENDATION: ~: 1) Receive Report 2) Approve installation of"No Right Turn On Red" signs prohibiting the right turn movement on red from Davona Drive onto Village Parkway FINANCIAL STATEMENT: Sufficient funds are budgeted in the Street Maintenance Operating Budget to cover the cost of posting signs. DESCRIPTION: Before traffic signals were installed along Village Parkway at Davona Drive, Brighton Drive, and Tamarack Drive, Council requested that Staff perform an "After" study to assess traffic speeds and safety after these signals were installed. With the new traffic signals in place and motorists familiar with their operation, Staff conducted a review of traffic circulation and safety, primarily focusing on the Village Parkway/Brighton Drive intersection due to its immediate proximity to Dublin High School and the direct impact that school traffic has on this intersection. The .Village Parkway intersections at Davona Drive and at Tamarack Drive were also evaluated and segment speed surveys were taken. This study was conducted during the critical time period between 7:30 and 8:30 a.m., which coincides with both school traffic and the morning commute peak hour. Field observations were conducted on five weekdays to collect representative information on traffic circulation along Village Parkway between Tamarack Drive and Davona Drive. Based on this study, the new traffic signals on Village Parkway between Tamarack Drive and Davona Drive were found to provide an efficient and enhanced school traffic safety system in the vicinity of Dublin High School (see Attachment, Traffic Report). The current vehicle and pedestrian timings of these traffic signals are appropriate based on field observations. Furthermore, Brighton Drive, where school traffic is heaviest in the vicinity of Dublin High School, has adequate signing and pavement markings for COPIES TO: Deputy Bruce Rank Dublin Unified School District Superintendent ITEM NO. G:X, AGENMISC\agst vp traffic safety.doc enhanced traffic and pedestrian safety. The current 35-mph speed limit on Village Parkway adjacent to the school was found to be adequate based on traffic speed surveys conducted in this area. Additional safety measures have been taken as a result of this traffic study. The green time for the northbound left turn movement on Village Parkway at Davona Drive was increased from 35 to 45 seconds to !better accommodate the heavy U-turn movement at this location during the morning peak hour. In addition, the City installed a 25-mph speed limit sign on Brighton Drive to reinforce the existing speed limit pavement marking in the eastbound direction between Village Parkway and Callan Street. Public Works Staff has also coordinated with Police Services on providing increased police patrols on Brighton Drive during school traffic periods to ensure that students drive safely on this street. In order to improve the efficiency of the newly-signalized intersections on Village Parkway in the vicinity of Dublin High School, City Staff has made timing adjustments at these intersections to make the signals more responsive to side street traffic for vehicles approaching Village Parkway on Davona Drive, Brighton Drive and Tamarack Drive. These timing adjustments have increased the probability of the traffic signal changing to green for the side street by the time an approaching vehicle proceeds to enter the intersection. Due to the limited sight distance of southbound traffic on Village Parkway when making a right turn from Davona Drive, Staff recommends installing "No Right Turn On Red" signs at this intersection to prohibit the right turn movement on red from Davona Drive onto Village Parkway. Finally, because of the sporadic nature of traffic accidents that have occurred at Village Parkway/Brighton Drive within the last three years, Staff will closely monitor this intersection and, if necessary, implement additional safety measures to help prevent accidents at this location. Staff recommends that Council receive this Report and approve installation of "No Right Turn On Red" signs prohibiting the right turn movement on red from Davona Drive onto Village Parkway. TRAFFIC REPORT Evaluation of Traffic Circulation and Safety in the Vicinity of Dublin High School April 25, 2002 This traffic report summarizes the findings of a traffic circulation and safety study conducted on Village Parkway in the vicinity of Dublin High School after traffic signals at Davona Drive, Brighton Drive, and Tamarack Drive were installed. This study focused primarily on the Village Parkway/Brighton .Drive intersection due to its immediate proximity to Dublin High School and the direct impact that school traffic has on this intersection. The Village Parkway intersections at Davona Drive and at Tamarack Drive were also evaluated and a traffic speed review was conducted on Village Parkway in the vicinity of Dublin High School. The study analysis was performed during the critical time period between 7:30 and 8:30 a.m., which coincides with both school traffic and the morning commute peak hour. Field observations were conducted on February 6, 7, 12, 13 and 14, 2002 to collect information on traffic circulation along Village Parkway between Tamarack Drive and Davona Drive. The findings of this study ar6 Summarized below. Village Parkway/Brighton Drive Traffic and pedestrian counts were collected at the intersection of Village Parkway/Brighton Drive during the morning peak hour between 7:30 and 8:30 a.m. The traffic count indicated that certain movements at this intersection are considerably heavy during this time period, including the northbound/southbound through movements on Village Parkway and the left/right turn movements from Village Parkway onto Brighton Drive. The average cycle length measured in the field for the traffic signal at this intersection is 80 seconds. This traffic signal is currently running in a fully actuated free mode and is not coordinated with other traffic signals on Village Parkway. A maximum queue length of 10 vehicles per lane was observed during the red interval for the southbound through movement on Village Parkway. On the northbound approach of the intersection, most traffic backups occur in the rightmost lane (which is shared by through and right turn traffic), as parents driving to school tend to utilize this lane to travel through the intersection and drop off children along Village Parkway north of the intersection. In addition, students driving to school also utilize this lane to tum right onto Brighton Drive to access the school's parking lot. Queuing conditions in this lane are still acceptable (e.g., the maximum queue is kept to 15 vehicles or less) during the red interval, as this lane is wide enough to allow the right turning vehicles to form a separate lane adjacent to the through vehicles. The green time for through traffic on Village Parkway is long enough to clear all of the above queues. Pedestrian counts were also collected at the intersection of Village Parkway/Brighton Drive during the morning peak hour between 7:30 and 8:30 a.m. For the most part, students use the northerly crosswalk of the intersection to cross Village Parkway and generally cross in groups of two to four students. As students arrive at the intersection to cross Village Parkway, the pedestrian push button is pushed and the wait is approximately 20 seconds, on average, until the Walk indication comes on, allowing the students to cross. The programmed pedestrian crossing time is 29 seconds (including the Walk and Flashing Don't Walk intervals), which is sufficient for students to cross Village Parkway safelY, as confirmed by field observations. The above' pedestrian delay of 20 seconds is considered reasonable and Pedestrian- friendly for a congested signalized intersection such as the Village parkway/Brighton DriVe intersection during the morning peak hour. It is always important to maintain a relatively short pedestrian delay at signalized intersections around school areas due to safety considerations. For this reason, the City will continue to operate the traffic signal at this intersection in a free mode (i.e., no coordination with adjacent traffic signals) to minimize pedestrian delay. Staff also conducted an operational level of service (LOS) analysis at the Village Parkway/Brighton Drive intersection during the morning peak hour using the newly- acquired HiCAP 2000 software. This type of analysis requires entering traffic signal timings into the model, as well as traffic and pedestrian volumes, to simulate the actual operation of a signalized intersection. The overall LOS for the intersection is then calculated based on the average delay in seconds per vehicle. According to this analysis, the aVerage delay at this intersection is approximately 30 seconds per vehicle during the morning peak hour, which is equivalent to an acceptable LOS of "C." Staff further validated the output of this operational analysis by confirming that the calculated intersection delay was consistent with the actual delay observed on a random basis in the field. In general, the new traffic signal at the intersection of Village Parkway/Brighton Drive is providing an efficient and safe traffic circulation system for both vehicles and pedestrians in the vicinity of Dublin High School. Village Parkway/Davona Drive Field observations were conducted at the intersection of Village Parkway/Davona Drive during the morning.peak hour between 7:30 and 8:30 a.m. The northbound U-turn movement is the heaviest traffic movement at this intersection during this time period. After parents drop off children on Village Parkway north of Brighton Drive, the majority of the parents Proceed to make a U-turn to southbound Village Parkway at Davona Drive. Queues in excess of 15 vehicles were observed forming during the red interval and. blocking the leftmost northbound through lane on Village Parkway to make this U-turn. As a result, the green time for the northbound left turn movement (which also services the U-turn) was increased from 35 to 45 seconds to ensure that the back of the queue for the U-turn clears regularly during the green interval. The southbound through movement also backs up at this intersection during the morning peak hour. A maximum queue length of 10 vehicles was observed in the single southbound through lane on Village Parkway during the red interval. This queue clears regularly during the green interval and is expected to decrease in size by half once the current CIP project to widen the southbound approach (to include two through lanes and one U-turn lane) is completed this spring. Dublin High School students who reside in the Davona Drive area and walk to school use the Village Parkway/Davona Drive intersection on a regular basis to cross Village Parkway. The programmed pedestrian crossing time is 27 seconds, which is sufficient for students to cross Village Parkway safely, as confirmed by field observations. In general, the new traffic signal at this intersection has enhanced traffic and pedestrian safety in the vic!nity of Dublin High School. Other intersections observed as part of this traffic study included Village parkway/Tamarack Drive and Village Parkway/Amador Valley Boulevard. Traffic conditions are moderate at the intersection of Village Parkway/Tamarack during the morning peak hour due to the low turning movement volumes and moderate pedestrian activity at this intersection. At Village parkway/Amador Valley Boulevard, the southbound left turn movement onto eastbound Amador Valley Boulevard is somewhat heavy, as many parents driving away from Dublin High School make this left turn. However, the green time for this movement is long enough to clear the traffic queues on this approach. Traffic Circulation Review Based on field observations, parents driving to Dublin High School drop off children in an orderly manner using the marked shoulder area on the eastside of Village Parkway north of Brighton Drive. These school-related trips seem to make up the majority of traffic traveling northbound on Village Parkway during the morning peak hour and do not appear to create traffic flow problems on Village Parkway. Most students driving to school use Brighton Drive in the eastbound direction to access the school's parking lot entrance located east of Callan Street. A large number of walking students use the Brighton Drive/Callan Street intersection to cross Brighton · Drive to the school. This T-intersection has yellow crosswalks to alert motorists to the. presence of a school crossing and is controlled by three-way Stop signs. "Stop Ahead" warning signs and pavement markings also exist in both directions of Brighton Drive in advance of the Callan Street intersection for added safety. The speed limit on Brighton Drive is 25 mph and is indicated on the pavement with a white "25" marking in the eastbound direction between Village Parkway and Callan Street. In addition, the City has recently installed a speed limit sign at this location to supplement the "25" pavement marking. Traffic congestion tends to develop and dissipate quickly on Brighton Drive due to the sporadic surges of vehicle and pedestrian traffic into a short segment of Brighton Drive between Village Parkway and Callan Street. Public Works Staff has coordinated with Police Services on providing increased police patrols on Brighton Drive during school traffic periods to ensure that students drive safely and patiently on this street. In general, school-bound vehicle and pedestrian traffic seems to circulate efficiently and safely both on Village Parkway and on Brighton Drive during the morning peak hour, based on field observations. Traffic Speed Review A traffic speed review was conducted on Village Parkway in the vicinity of Dublin High School to assess the impact of thc new traffic signals at Tamarack Drive, Brighton Drive, and Davona Drive on traffic speeds on Village Parkway. Traffic speed data were collected in August and October 2001 to analYZe this impact with and without Dublin High School traffic. The posted speed limit on Village Parkway is 35 mph between Tamarack Drive and the northern City limit. This speed limit was based on a speed survey conducted on December 15, 1999, which showed the critical speeds on this segment of Village Parkway ranging between approximately 37 and .39.5 mph. The Critical speed, also known as the 85th percentile speed, describes the speed below which 85% of the drivers operate. This speed is generally used as a benchmark for establishing a speed limit. Police Services placed a speed trailer on Village Parkway (between Tamarack Drive and Davona Drive) on August 13, 14 and 15, 2001, before the beginning of the 2001/02 scholastic year, and collected speed data between 7:00 AM and 7:00 PM in both directions of travel. Based on this 3-day survey, it was found that the average speeds on Village Parkway ranged between 30 and 32 mph, and the critical speeds ranged between 36 and 37 mph. Since these speeds are similar to those from the 1999 speed survey, it was determined that the new traffic signals on Village Parkway, between Tamarack Drive . and Davona Drive, have not caused traffic speeds to increase on Village Parkway. In grder to assess the impact of school traffic on speeds on Village Parkway, Police Services placed a speed trailer on Village Parkway (between Tamarack Drive and Davona Drive) on October 3 and 4, 2001 between 7:00 AM and 1:00 PM. Based on this survey, it was found that the average speeds ranged between 29 and 32 mph, and the critical speed measured 37 mph. The survey' also showed that Dublin High School traffic was causing the average speed on Village Parkway to drop slightly in the morning (e.g., from 31.5 to 29.5 mph) due to increased traffic congestion as students arrive at the school. In summary, the speed surveys taken before and after the start of the 2001/02 scholastic year suggest that school traffic is not causing traffic speeds to increase on Village Parkway, and that the current 35-mph speed limit is adequate and should remain , unchanged. Accident History Review A review of reported traffic accidents that occurred on Village Parkway between Tamarack Drive and Davona Drive in 1999, 2000 and 2001 was conducted as part of this study. The new traffic signals at Tamarack DriVe and at Brighton Drive were activated on March 14, 2001, and at Davona Drive on March 21, 2001. Prior to those dates, these intersections were controlled by all-way Stop signs. For the Village Parkway/Tamarack Drive intersection, one accident per year was reported during this three-year span. At Village Parkway/Davona Drive, one accident per year was reported in 1999 and 2000, and two accidents were reported in 2001. This information indicates that these two intersections have been low-accident locations under Stop sign or traffic signal control. At Village Parkway/Brighton Drive, the reported traffic accidents include six accidents in 1999 (including four fight-angle accidents), one accident in 2000 (right-angle), and six accidents in 2001 (including five right-angle accidents). Based on this information, this intersection was a high-accident location in 1999 and 2001. However, it is difficult to establish a trend for accident occurrences at this intersection, simply because the number of accidents varies considerably from year to year and does not show COnsistency. For example, only two accidents were reported at this intersection in 1998 and one accident was reported in 2000. No accidents have been reported thus far in 2002. In summary, it cannot be determined at this point what positive impact the new traffic signal might have had at this intersection in terms of lowering the accident rate. Based on the above findings, City Staff will closely monitor the intersection of Village parkway/Brighton Drive to ensure that accident occurrences are kept to a minimum at this location. Traffic Signal Equipment Placement City Staff was recently contacted by a Dublin resident with a concern that newly-installed 'traffic signal cabinets are blocking the sight distance of southbound traffic on Village Parkway when making a right turn from Davona Drive, Brighton Drive or Tamarack Drive. Staff explained to this citizen that existing utilities present at these ,intersections played a significant role in the placement decision of the signal cabinets. For example, at the Village parkway/Tamarack Drive intersection, the southwest cOmer contains PacBell utilities that would have made it difficult to install the signal cabinet and accompanying conduits and pull-boxes on this comer without interfering with these utilities. On the east side of the intersection, there is not enough space to accommodate the cabinet. Similarly at the Village Parkway/Brighton Drive intersection, there are PacBell utilities at the southwest comer of the intersection that would have made it difficult to accommodate the signal cabinet installations on this comer. On the southeast cOmer of the intersection, there is not enough space to accommodate the cabinet. The cabinet could have been placed on the northeast comer; however, the fact that this is a school comer made this location undesirable as it was necessary to avoid contact with schOol students. At Davona Drive, it would have been possible to locate the cabinet on the southwest comer of the intersection. However, the consultant who designed the traffic signal opted to locate the cabinet at the northwest comer because the PG&E power service point is also located on this comer. It would have been also possible to locate the cabinet on the east side south of the intersection to avoid sight distance problems. However, the sight distance of southbound traffic on Village Parkway when making a right turn from Davona Drive is limited primarily due to the horizontal curvature of Village Parkway in the vicinity of Davona Drive. Looking north, the street curves to the west, which does shorten the sight distance to approaching southbound traffic. Due to these sight distance considerations and based on field observations, City staff recommends installing "No Right Turn On Red" signs at this intersection to prohibit the right turn movement on red from Davona Drive onto Village Parkway. City Staff has also made timing adjustments at those three intersections to make the signals more responsive to side street traffic as vehicles approach Village Parkway on Davona Drive, Brighton Drive or Tamarack Drive. These timing adjustments will increase the probability of the traffic signal changing to green for the side street by the time an approaching vehicle proceeds to enter the intersection: Summary Based on this traffic study and field observations conducted during the morning peak hour between 7:30 and 8:30 a.m., the new traffic signals on Village Parkway between Tamarack Drive and Davona Drive are providing an efficient and enhanced school traffic safety system in the vicinity of Dublin High School. The current vehicle and pedestrian timings of these traffic signals are appropriate based on field observations. Furthermore, Brighton Drive where school traffic is heaviest in the vicinity of Dublin High School has adequate signing and pavement markings for enhanced traffic and pedestrian safety. However, additional safety measures have been taken as a result of this traffic study. For example, the green time for the northbound left turn movement on Village Parkway at Davona Drive was increased from 35 to 45 seconds to better accommodate the heavy U- turn movement at this location during the morning peak hour. In addition, the City installed a 25-mph speed limit sign on Brighton Drive to reinforce the existing speed limit pavement marking in the eastbound direction between Village Parkway and Callan Street. Public Works Staff has also coordinated with Police Services on providing increased police patrols on Brighton Drive during school traffic periods to ensure that students drive safely and patiently on this street. In order to improve the efficiency of the newly-signalized intersections on Village Parkway in the vicinity of Dublin High School, City Staff has made timing adjustments at these intersections to make the signals more responsive to side street traffic as Vehicles approach Village Parkway on Davona Drive, Brighton Drive or Tamarack Drive. These timing adjustments will increase the probability of the traffic signal changing to green for the side street by the time an approaching vehicle proceeds to enter the intersection. Due to the limited sight distance of southbound traffic on Village Parkway when making a right turn from Davona Drive, City Staff recommends installing "No Right Turn On Red" signs at this intersection to prohibit the right turn movement on red from Davona Drive onto Village Parkway. Finally, because of the sporadic nature of traffic accidents that have occurred at Village Parkway/Brighton Drive within the last three years, City Staff will closely monitor this intersection and, if necessary, implement additional Safety measures to help prevent accidents at this location.