Access management strategies are devised to facilitate travel mobility and improve safety. Direct access especially left-turns in and out of developments can create significant problems for the traffic flow and safety on the adjacent roadway and at the driveways. This study evaluates the safety and operational impacts under various access configurations, and provides basic guidelines as to when left-turns at driveways should be prohibited. The safety considerations were found to be less significant compared to the operational concerns since the crash reductions that might be expected from access restrictions appeared to be relatively modest. The importance of review of crash history by site is emphasized. Traffic simulation models were developed using VISSIM to analyze the operational impacts of driveway turning restrictions at corner and mid-block sites. The results indicate that lesser the corner clearance, more negative is the impact on driveway related delays. Also, the negative impact due to mainline volume increment was more severe as compared to the increment in driveway volume. The impact on the driveway operations was worse when the number of lanes on the adjacent roadway was less than 5 or 4. The right-turn (in or out) driveway traffic was not critical from either the operations or safety perspectives due to fewer conflict points. General guidelines are proposed for prohibition of left-turns in and out for various combinations of mainline and driveway traffic volumes and corner clearances. (Author/publisher)
Samenvatting