Incident Warning Systems and Traffic Safety: A Comparison Between the PORTICO and MELYSSA Test Site Systems

Abstract

In this study we compared the effects on traffic safety of 2 different incident warning systems (IWSs), capable of presenting warning messages with different levels of detail. It was assumed that an IWS presenting a message with a low level of detail (i.e., "Warning") would produce a higher variation in driver behavior compared to a system that presented more detailed information (i.e., "Warning, in 1 km, use left lane"). The assumption was tested in a simulator study in which the Portuguese Road Traffic Innovations on a Corridor and Mediterranean Lyon Stuttgart Site for Advanced Transportation Telematics test site systems were simulated and used to present information that varied in level of detail in 4 steps. Fifty participants drove an 80-km route on a 2-lane motorway, where 3 different incidents occurred at randomly chosen distances from the starting point. The results showed that all IWSs made the participants reduce their speed level earlier compared to the control group. Subjective assessment of the IWS showed positive effects, and there was a tendency of a reduction of mental workload caused by the IWS. The assumption that a low level of detail in a message from an IWS would cause a higher variation in the participants' behavior, compared to a message with more detailed information, was not supported. Specific information from an IWS (i.e., "Change lane") resulted in 2 different strategies: One implied that the participant should trust and obey the recommendation, and the other implied that the participant should wait until the warned-for incident was visible and then follow the advice. The implications for the design of IWSs, as a consequence of the results from this study, are discussed.