PLANNING AND DESIGN OF PASSING LANES USING SIMULATION-MODEL

The present paper describes the planning and preliminary design of pas sing lanes in difficult terrain in Southern California and is based on an investigation of approximately 560 km (350 mi) of two-lane highway s in Imperial, San Diego, and Riverside counties. The need for passing opportunities has arisen for several reasons, the most important bein g the fact that long sections of highways are marked as no passing zon es, which leads to extensive delays, driver frustration, and increased accidents. The planning techniques described herein include the use o f video-logs to create a computer file documenting existing highway co nditions and a two-lane highway simulation model. The TRARR (traffic o n rural roads) simulation model was used to determine the impact of pr oposed passing lanes and turnouts on level of service. The use of the simulation model allowed the evaluation of a range of passing lane alt ernatives (including length and location) for a wide range of traffic, vehicle, and driver characteristics. In total, 117 new passing lanes and four turnouts were recommended for the 560 km (350 mi) of State ro utes that were evaluated.