Statistical Models for Preferred Time Headway and Time Headway of Drivers in Steady State Car-Following


This paper proposes two shifted continuous distribution models for preferred time headway (Tp) and time headway of drivers in steady state car-following (Tws), i.e. the lognormal and gamma models. Lognormal distribution with a shift of 0.21 seconds provides a good fit to Tp, whereas a shift of 0.26 is proposed for Tws. Similarly, shifted Gamma distribution is proposed for Tp and Tws with shifts of 0.21 seconds and 0.26 seconds, respectively. Detailed data sets (FHWA Data) observed at one-second intervals collected from aerial photography for four sites have been used in this paper. The data sites are a basic freeway section, a ramp merge, a lane drop and a ramp weave section. Tp and Tws were found to be the shortest (mean, median and st. dev.) on the ramp weave section compared to all other sites. It was also found that the shifted Lognormal distribution provided a better fit to all the observed sites compared to the shifted Gamma distribution.

Meeting Name

9th International Conference on Applications of Advanced Technology in Transportation


Civil, Architectural and Environmental Engineering

Keywords and Phrases

Driver Behavior

Library of Congress Subject Headings

Automobile drivers
Traffic flow

Document Type

Article - Conference proceedings

Document Version


File Type





© 2006 American Society of Civil Engineers (ASCE), All rights reserved.