Time Headway Analysis for Four-Lane and Two-Lane Roads

Study of vehicle time headways has been a subject to many aspects of traffic flow studies because time headway between any two successive vehicles is considered as an important parameter affecting capacity, safety, delay, driver behavior and level of service of a transportation system. Although a large number of studies exist in the field of time headway modelling, there is still a paucity of research related to time headway distribution study in two-lane bidirectional roads and four-lane divided roads with respect to varying flow rate levels. The present paper intends to study the variations in time headway distributions for four flow levels (0–600, 600–1200, 1200–1800 and 1800–2400 PCU/h) for different two-lane and four-lane roads in Assam, with traffic data collected from video-recorders. It is further aimed to investigate the differences in headway maintaining behavior of vehicles in morning hours and in evening hours (in presence of headlights) when the flow rates for the analyzed periods are comparable. Also vehicle-type specific headway analysis is conducted for two-lane bidirectional roads. The result of this paper not only identifies the difference in time headway distributions of mixed vehicular flow for different flow levels but also captures the differences in vehicle-type specific headways and headway maintaining behavior of vehicles when the headlights of vehicles are turned on. Results of the study can be used as an input in practical applications, especially for developing micro-simulation models and also can be used in capacity estimation, safety analysis, etc.