Research was conducted to assess the effects of warning time on driver behaviour and safety at railroad-highway grade crossings with active traffic control, i.e., Flashing light signals with and without automatic gates. The research included (a) an evaluation of driver response data gathered at three grade crossings in the Knoxville, Tennessee, area; and (b) a human factors laboratory study of drivers' warning time expectations and tolerance levels. In the field studies, the actions of over 3, 500 motorists were evaluated during 445 train events. Based on the study results, warning times in excess of 30-40 sec caused any more drivers to engage in risky crossing behaviour. The studies also revealed that the large majority of drivers who cross the tracks during the warning period do so within 5 sec from the time they arrive at the crossing. The human factors studies expanded the findings of the field evaluation. Specifically, the studies revealed that most drivers expect a train to arrive within 20 sec from the moment when the traffic control devices are activated. Drivers begin to lose confidence in the traffic control system if the warning time exceeds approximately 40 sec at crossings with flashing light signals and 60 sec at gated crossings. Based on the research, guidelines for minimum, maximum, and desirable warning times are presented. These guidelines are designed to minimise vehicles crossing during the warning period and promote driver credibility for the active control devices.
Abstract