Lane Closures at Freeway Work Zones: Simulation Study

A study of freeway lane closures at work zones is described. It involved the development of a microscopic computer-simulation model. Vehicles in platoons are controlled by a car-following rule. The merging behavior is controlled by the information provided by the traffic-control devices, by personal preference for early or delayed merge, and by the availability of gaps in the open lane. The prescription of personal preference was based on a driver survey. The model also checks for the possible obscuring of signs by large vehicles. Field tests produced varied results, but average speeds and throughput (vehicle miles per hour squared) generated by the model fit between the classical Greenshield’s model and those calculated by the 1980 revision of the Highway Capacity Manual. A factorial simulation study was conducted to investigate traffic behavior under a variety of conditions, represented by different volume levels, traffic compositions, merging preferences, speed control and compliance, and advance-warning distances. Delay and standard deviation of speed at the taper were generated for each factor-level combination. The results generally confirmed what was expected. Noteworthy is the indication that full compliance with a reduced speed limit of 45 mph would increase delayed merges within the taper area in the volume range simulated.