SR 05:293 - Laserfiche WebLink

indicated that the combination of morning commuter and school traffic would create very bad LOS F conditions at this intersection with a traffic back-up that would extend beyond the fire station. In the Specific Plan, Vineyard Avenue was to be built as a 2-lane rural roadway. There was a drainage culvert just east of this intersection that limited how long the left turn pocket could be for traffic waiting to turn onto the east school side street. Double left turn lanes are usually needed as traffic volumes approach 300 vehicles per hour. At this intersection, left turn volumes are expected to exceed 500 vehicles per hour, and these vehicles will all want to make their left turns in about a 15-minute period. At the same time, after dropping their students off, about this same amount of traffic will try to exit the school site. A single left turn lane 75 feet long was not adequate to handle this traffic, so all left turn and through traffic congested the one eastbound lane with left turns blocking through traffic and through traffic blocking left turners. During this same time period, staff was designing the roundabouts for Valley A venue south of Bernal A venue as part of the Bernal Properties specific plan. The federal design guidelines indicated that a roundabout designed like the ones on Valley Avenue would handle traffic volumes on Vineyard A venue near Neal School better than a traffic signal could. The roundabouts would work well on a 2-lane road and would not be affected by the proximity of the drainage culvert. Computer simulations of the roundabouts indicated that the continuous traffic flow around the roundabout would minimize any traffic back-ups east of the school. In addition, roundabouts would slow traffic adjacent to an elementary school being built along a 50 MPH roadway. Staff prepared computer simulations of both the double roundabout design and the traffic signal and presented them to the Ruby Hill Homeowners Association, the Fire Chief, the School District and some Vineyard Avenue residents. The consensus was that between the two options, the roundabouts were preferred, especially as they improved emergency access along Vineyard Avenue from the Fire Station. City Staff has again analyzed traffic circulation adjacent to Neal School with updated versions of the traffic simulation software with similar results to the original analysis. A traffic signal at this location would result in traffic back-ups beyond the Fire Station during the morning Peak Hour. The roundabouts result in less queuing and smoother traffic flow at the school, and 25 to 30 MPH speeds adjacent to the school. Staff then looked at the effect various changes to traffic volume projections or intersection lane configurations would have on traffic congestion at this intersection. This included assuming reductions in westbound left turn volumes, through volumes and roadway widenings to provide long double left turn lanes. In all cases, the roundabouts outperformed a traffic signal in terms of reduced stopped delay, significantly shorter traffic backups to the east of the intersection, and reduced speeds adjacent to the school. SR:05:293 Page 4 of 8