Effect of driving context on time to collision at brake application during car following

Collision Warning (FCW) systems that have customizable warning delivery settings may improve driver acceptance, thus increasing the benefits of such systems. In order to design FCW warning thresholds that match a driver's expectations, system designers need to characterize when the brakes are normally applied. However, a driver's normal braking behavior may vary with the driving context, e.g., traffic congestion or daylight conditions. This study examined over 2.6 million brake applications from the 100-Car naturalistic driving study to determine the effect of driver demographics (age group and gender) and driving context (day of week, time of day, travel speed, and traffic congestion) on brake application time. The results showed that both demographics and driving context were statistically significant indicators of the time to collision (TTC) that drivers applied the brakes during car following.