Choice of time-headway in car-following and the role of time-to-collision information in braking

Abstract

Time-headway (THW) during car-following and braking response were studied in a driving simulator from the perspective that behaviour on the manoeuvring level (e.g. choice of THW) may be linked to operational competence of vehicle control (e.g. braking) via a process of adaptation. Time-headway was consistent within drivers and constant over a range of speeds. Since time-headway represents the time available to the driver to reach the same level of deceleration as the lead vehicle in case it brakes, it was studied whether choice of time-headway was related to skills underlying braking performance. The initiation and control of braking were both affected by time-to-collision (TTC) at the moment the lead vehicle started to brake. This strongly supported the idea that time-to-collision information is used for judging the moment to start braking and in the control of braking. No evidence was found that short followers differ from long followers in the ability to accurately perceive TTC. There was, however, evidence that short followers are better able to programme the intensity of braking to required levels. Also, short followers tuned the control of braking better to the development of criticality in time during the braking process. It was concluded that short followers may differ from long followers in programming and execution of the braking response.

Driving performance and driver discomfort in an elevated and standard driving position during a driving simulation

“…These findings support those of Van Winsum (1996) who concluded that when drivers were able to judge the intensity of braking levels, they drove with consistently shorter headways. They also observed that both driving behavior and physical limitations contribute to selfselecting an appropriate headway.…”

“…good visibility, dry road conditions. However, in reality the headway allowed by a driver can be influenced by the traffic density, the characteristics of the driver (Jonah, 1996), the perceived ability to judge physical situations better than other drivers (van Winsum, 1996), as well as the physical capabilities of the vehicle and circumstantial factors surrounding the journey e.g. routine vs. urgent journey.…”

Determinants of following headway in congested traffic

“…Further studies will clearly be required to attempt to explain some of the features encountered, for example in terms of driver braking skill and experience (van Winsum and Heino, 1996) and indeed why drivers choose headways that are clearly less than their brake reaction times (an issue perhaps related to the lack of experience that most drivers have with anything more than low levels of braking, Touran et. al., 1999).…”

Estimating Suitable Probability Distribution Function of Risk for Different Traffic States

“…In these researches, TTC has often been used as a safety indicator for traffic risk by finding the minimum TTC [12].…”