Determinants of time headway in staggered car-following conditions

Precise understanding of the factors affecting the choice of following time headway in staggered car-following conditions is essential on the part of traffic modelers to provide a detailed representation of traffic flow, which has a predominant role in microsimulation model development, safety evaluation, capacity estimation and evaluation of traffic management strategies. Using trajectory data from video recordings, an evaluation of the impact of a number of factors (i.e. road width, centerline separation, lead vehicle type) on the following headway of a driver is undertaken in this study. A seemingly unrelated regression (SUR) model for time headways is also developed to examine the correlation of headways with different determinants and speeds of following vehicles. Results of the study suggest that though there is a direct relationship between speed and headway, the extent of off-centeredness between the interacting pair and vehicle type-specific interactions need to be considered to develop mixed-traffic microsimulation models.