Citation

Wu SS, Heimbach CL. Transp. Res. Rec. 1981; 806: 21-28.

Copyright

(Copyright © 1981, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

A summary is presented of research undertaken to develop a rural two-lane, two-way computer simulation model that could be used by the highway design practitioner to measure and evaluate traffic-flow consequences for various alternatives considered during the roadway design process. To this end, a microscopic computer simulation model written in FORTRAN was developed. For the simulation roadway, the model can incorporate vertical grades, intersecting side roads, climbing lanes, and no-passing zones. Traffic and speed data used by the model include driver desired speeds, overall posted speed for the highway, localized speed restrictions, individual main-road traffic lane volumes, side-road traffic volumes, vehicle composition in five categories, and vehicle acceleration and deceleration characteristics. Throughput statistics for use in design evaluation include distributions of space mean speed and speed change and a traffic-flow quality index. Effects on traffic flow of spot improvements in roadway geometry or traffic control can be obtained by placing windows in the program at specified locations. Output data are summarized and reported at user-specified time intervals. By using a FORTRAN level H compiler, the simulation model has been run on an IBM 370/165 computer. For an 8000-m (4.9-mile) long roadway and a real-time simulation of 3600s, as two-way traffic volume varied from 400 to 800 vehicles/h, the actual computer time varied from 28.3 to 62.3s. Model validation tests were performed and the results were found to be consistent with actual traffic-flow patterns. In addition, the model was applied to an actual field site, where the base condition and three redesign alternatives were simulated.