Springwoods Drive Improvements
When Prince William County recognized a need for a separate turning lane on Springwoods Drive at the Old Bridge Road intersection in Occoquan Virginia, the county chose AMT to perform subsurface utility designation, surveying, traffic studies and transportation engineering for the project.
AMT performed traffic studies to identify right turn traffic volumes and optimal storage length. Field Data Collection consisted of extensive field visits and survey data collection to support both the traffic and design portions of the project. Roadway geometrics, signal timings/phasing, existing storage lane lengths, amongst other key elements were collected. Traffic Counts included the collection of 13-hour weekday turning movement counts at this key intersection. The traffic counts were tabulated to provide the AM and PM peak hours for the traffic analyses. Signal Phasing and/or Timing Recommendations were anticipated based on the widening of the roadway and the modified lane use, and included allowing for right-turn-on-red versus prohibiting those, modeling the right turns as an overlap to the mainline left turns.
Intersection/Corridor Analysis included detailed analyses of the actuated coordinated signal that controls the intersection today using Synchro/SimTraffic, as well as HCS+. The capacity analyses at the intersection were based on a number of different design concepts to determine the existing LOS, delays, and anticipated southbound queues to correctly determine the required storage length for the southbound right turn movement. Based on the results of the traffic analyses, Springwoods Drive was widened from two southbound lanes to three southbound lanes to provide a separate southbound right turn lane, a shared through-left turn lane, and a separate left turn lane. The capacity analyses indicated that the intersection would operate at an acceptable LOS overall (LOS “C”).
The project included adding a signal head as well as two audible countdown pedestrian signals, roadway striping, modifications to an existing closed drainage system and culvert, a mechanically stabilized earth aesthetic retaining wall, adding a sidewalk and other pedestrian facilities including detectible warning surface on the CG-12 ramps.
Coordination with VDOT was provided throughout.