Driver’s timing of the Forward Collision Warning: are they different under same relative speed?

Forward Collision Warning System (FCWS) is a system that allows a vehicle to detect its distance from the vehicle in front of it. It can help drivers avoid rear-end collisions. A more precise warning timing can make FCWS more effective but the timing seems to vary when judged by drivers under different subject vehicle speeds. This paper aims to assess the proper collision warning timing (CWT) under different subject vehicle speeds. A driving simulator was conducted to study drivers’ selections of the CWT at different speeds. In total, 20 drivers were tested in a within-subject design. They were arranged to perform experiment in two scenarios. In Scenario I, drivers were asked to decelerate subjectively according to traffic condition under different subject vehicle speeds. While in Scenario II, the optimum CWT was derived by drivers’ selection of these timings. After analyzing the data of both scenarios, it can be concluded that drivers preferred early CWT under high subject vehicle speed even when the relative speed was kept constant. This finding supplement the method to calculate the proper CWT. Further studies are needed to examine whether drivers characteristic or gender affect the CWT.