This study is the second in a series of four experiments exploring human factors issues associated with the introduction of cooperative adaptive cruise control (CACC). Specifically, this study explored drivers’ abilities to merge into a stream of continuously moving vehicles in a dedicated lane. Participants were asked to complete one of three different types of merges in the Federal Highway Administration Highway Driving Simulator: • Merge with non-CACC vehicle into a left dedicated lane without CACC platooning and varying vehicle gaps. • Merge with CACC vehicle into the middle of a CACC platoon or continuous stream of vehicles without speed assistance. • Merge with CACC vehicle into a CACC platoon with longitudinal speed assistance. As measured by the National Aeronautics and Space Administration Task Load Index, drivers’ perceived workload was significantly less for both groups that drove with the CACC system engaged than for the group that was required to manually maintain speed the entire drive. Perhaps surprisingly, participant condition did not significantly affect physiological arousal as assessed by galvanic skin response (GSR). However, across all groups, GSR was significantly greater during the merges than during cruising/straight highway driving time periods. The participants who drove with the CACC system during the merges (as defined by the operation of the system) did not experience any collisions. Both groups that were required to manually adjust speed to merge into the platoon of vehicles experienced collisions in 24 (18 percent) of the merges, suggesting that some gaps may be too small for drivers to merge into at high speeds. An alternative explanation, supported by participant feedback, is that drivers expect others to act in a courteous manner and to create larger gaps for entrance onto a freeway– something that may not be possible in real-world CACC deployment. (Author/publisher)
Abstract