Citation

Hao H, Ma W. Transportmetrica B: Transp. Dyn. 2017; 5(1): 1-14.

Copyright

(Copyright © 2017, Hong Kong Society for Transportation Studies, Publisher Informa - Taylor and Francis Group)

DOI

10.1080/21680566.2015.1072484

PMID

unavailable

Abstract

The departure headway is one of the critical parameters to optimise and evaluate the design and timing of signalised intersections. In order to provide a suitable method to accurately estimate saturation headway at signalised intersections, the distribution of departure headways and its characteristics were investigated based on field observation in Shanghai, China. Statistical analysis results reveal that (1) Shifted Log-Normal distribution can be used to capture the features of departure headways distribution at each position in a queue, including headways at the first position which are usually excluded in existing models; (2)Shifted Log-Normal is more suitable to capture the distribution of steady-flow headways which are approximately the headways at positions between the fifth vehicle and the last stopping vehicle in the queue; (3) the mode of steady-flow headway distribution, which reflects the real manipulative ability of drivers in a certain region, can be considered as theoretical saturation headway and the mean can be considered as practical saturation headway which is used for actual capacity analysis in practice; and (4) saturation headway distribution obeys four-sigma rule. These findings about departure headway distribution at signalised intersections will be helpful for driving behaviour understanding, capacity calculation, design, timing, as well as microscopic traffic simulation of signalised intersections.

Language: en

Keywords

departure headway; practical saturation headway; Shifted Log-Normal distribution; signalised intersection; theoretical saturation headway