Safety Implications of Managed Lane Cross Sectional Elements

2016Jones, GregPDFTech ReportFHWA-HOP-16-076Contract No. DTFH61-12-D-00046Task Order No. T-5012Managed lanesTraffic safetyRoad shouldersUnited StatesUnited States. Federal Highway Administration. Office of OperationsFitzpatrick, KayAvelar, RaulUnited States. Federal Highway Administration. Office of OperationsBattelleTexas A&M Transportation InstituteJones, Gregory M.Federal Highway AdministrationThe objective of this project was to investigate the relationship between crashes and buffer-separated manage lane dimensions. The results from several previous research studies have demonstrated that reductions in freeway lane width or shoulder width are associated with more crashes. A wider managed lane envelope widths (i.e., left shoulder, managed lane, and buffer width combined) are also associated with fewer freeway crashes for both all severity levels and fatal and injury severity levels. Wider envelopes are associated a reduction of 2.8 percent (in Texas) or 2.0 percent (in California) in total freeway crashes (all severities) for each additional foot of envelope width. In California, wider envelopes are associated with a reduction of 4.4 percent in managed lane-related crashes (fatal and injury severity levels) for each additional foot of envelope width. The analysis was conducted on non-weaving managed lane segments that included a single managed lane separated from the general purpose lanes with a flush buffer area. The dataset included crashes on 128.0 miles in California (all 128.0 miles with flush buffers) and 60.4 miles in Texas (41.7 miles with pylon buffers and 18.7 miles with flush buffers). The California sites included freeways with three or four general-purpose lanes while the Texas freeways had three to five general-purpose lanes.83