Citation

Khasnabis S, Heimbach CL. Transp. Res. Rec. 1980; 772: 44-51.

Copyright

(Copyright © 1980, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

The distribution of vehicle headways on two-lane, two-way roadways has been the subject of continuing research for a number of years. The growing interest in headway-generation models is related to the increased application of simulation techniques to describe traffic-flow patterns through the use of digital computers. A headway-distribution model developed for varying traffic-volume conditions (80-630 vehicles/h/lane) is described. The model was developed as part of a research project on the feasibility of using simulation techniques for depicting traffic flow on two-lane highways. A total of 18 sets of headway data (2 sets for each site) were collected from nine sites in North Carolina. The process of model development consisted of testing the field data by using a number of existing simple models and progressing with increasing degrees of complexity until an acceptable match between the field data and the model output was obtained. The study showed that none of the existing models (the Negative Exponential, Pearson Type III, and Schuhl models) provided satisfactory results for the wide range of traffic volumes tested. A modified form of the Schuhl model, incorporating parameters developed from the North Carolina data, provided the most reasonable approximation of the arrival patterns noted in the field. Parameters developed in the study are presented, along with a nomograph that can be used by traffic researchers to describe the time spacing between successive arrivals of vehicles on two-lane highways.