An Empirical Analysis of Time Headways on Two-Lane Roads with Mixed Traffic
This paper demonstrates a method of describing headways of two-lane roads under mixed traffic situation using statistical distributions. Characteristically such distributions may have two forms: single and mixture of two or more distributions. A single distribution, however, cannot describe headways in the event of significant proportion of shorter headways in traffic. Use of mixed models is appropriate in such situation since they describe headways by decomposing them into free and following component. Based on experiences with mixed traffic and field studies on two-lane highways of India, this paper has shown that Cowan’s M3 can be reasonably applied for modeling headways up to a flow level that corresponds to ‘moderate to heavy flow’. However, since shifted negative exponential distribution part of the Cowan’s M3 distribution cannot model short headways, Cowan’s M3 distribution cannot model headway data at congested state of flow when almost all the vehicles in the traffic stream start moving in following.
KeywordsMixed traffic Headway distributions Mixed model
The part of the analysis presented in the paper has used the data collected in the CSIR-CRRI, New Delhi sponsored project “Development of Indian Highway Capacity Manual (INDO-HCM)”. The authors sincerely acknowledge CSIR-CRRI. The authors are grateful to the anonymous referees for their suggestions to improve the paper.
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