Cooperative Adaptive Cruise Control: Driver Acceptance of Following Gap Settings Less than One Second

Currently, Adaptive Cruise Control (ACC) systems can automate vehicle speed control to maintain following time-gaps in the range of one to two seconds. In this study, a field test was conducted to determine whether or not drivers would be comfortable with the sub-second following time-gaps that could be provided by a Cooperative ACC (CACC) system. A CACC system uses vehicle-vehicle communication to enable faster system responses and shorter following time-gaps. Sixteen drivers from the general public drove both systems on their daily commuting trips, and their driving behavior and subjective opinions of the systems were recorded. The results show that the drivers were generally comfortable with and typically selected the sub-second following time-gaps offered by the CACC system, but there were significant differences between the preferences of male and female drivers. The male drivers typically preferred the shortest gap settings, while the female drivers typically preferred slightly longer gap settings. The drivers' willingness to accept the shorter following gaps adds credibility to the assertion that future CACC systems may have the potential to produce significant increases in the achievable highway lane capacity.