Cooperative Adaptive Cruise Control Human Factors Study

Chapter 6. Conclusions

The results of experiment 1 (see chapter 2) and experiment 3 (see chapter 4) suggest that CACC could provide a substantial safety benefit as long as a salient alarm is triggered when the driver needs to intervene. Such an alarm is advisable even if CACC is implemented with full braking authority because the driver might want to steer rather than brake in some crash imminent circumstances.

Experiment 2 results (see chapter 3) strongly suggest that CACC should be accompanied with merge or steering assist to allow drivers to comfortably and safely merge into the smaller gaps between vehicles. Although most drivers in experiment 3 eventually learned how to adjust their speed to merge into smaller gaps, the learning curve included more collisions than would be desirable.

Experiment 4 results (see chapter 5) suggest that drivers’ preferences for following distance (gap) do not affect driver performance relative to an automated gap. Drivers adjust their performance appropriately for the actual gap, and designers do not need to be concerned about individual gap preferences, at least as it relates to driving performance.

Experiments 1, 3, and 4 assessed driver workload with and without CACC. In all three experiments, CACC was perceived to reduce driver workload.

The research summarized in this report suggests that CACC can reduce driver workload while enhancing safety. However, CACC is only one of many vehicle automation technologies in development or early deployment. The role of the driver will be in flux for years to come as putative safety and convenience automation technologies proliferate. Human factors research will need to focus on the ever-changing role of the driver and the resulting effects on the performance of these driver-vehicle systems.