Safety and Design Improvements at Rural Expressway Median Crossovers (Phase II)

摘要

Expressway medians separate opposing lanes of traffic. Crossovers in medians provide protection and control for cross and turning traffic. This study provides a means for the Missouri Department of Transportation to determine whether particular highspeed rural expressway crossovers are performing satisfactorily and, if not, to assess alternatives for crossover design. Design practices of other states were examined and alternative design options were identified. The Highway Capacity Manual (HCM) approach and the CORSIM simulation technique were compared to determine how best to identify appropriate alternatives. A procedure was then developed to assist district traffic and design engineers in selecting improvements for existing crossovers as they become congested. The procedure includes a diagram showing the combinations of highway volumes compatible with specific design alternatives.