Impact on driving performance of intelligent speed adaptation, following distance warning and seatbelt reminder systems: key findings from the TAC SafeCar project

Abstract

This study aimed to evaluate the impact of three ITS technologies, alone and in combination, on performance and safety. The three technologies were: intelligent speed adaptation (ISA); following distance warning (FDW) and seatbelt reminder (SBR). Each SafeCar was also equipped with daytime running lights (DRL) and reverse collision warning (RCW). Twenty-three fleet car drivers (15 treatments and 8 controls) each drove a SafeCar for 16 500 km. Treatment drivers were exposed to all ITS technologies, while control drivers were exposed to SBR, RCW and DRL only. Overall, ISA, FDW and SBR had a positive effect on driving performance. ISA reduced mean, maximum and 85th percentile speeds, and reduced speed variability in most speed zones. ISA also reduced the percentage of time drivers spent travelling above the speed limit, but did not increase commuter trip times. FDW significantly increased mean time headway and reduced time headway variability. Interaction with the SBR system led to large decreases in the percentage of trips where occupants were unrestrained, the percentage of total driving time spent unrestrained and the time taken to fasten a seatbelt in response to seatbelt warnings. However, the positive effects of these systems persisted only while they were active. Recommendations are made for the wider-scale deployment of the systems.