Driving With a Partially Autonomous Forward Collision Warning System: How Do Drivers React?

Objective: The effects of a forward collision warning (FCW) and braking system (FCW+) were examined in a driving simulator study analyzing driving and gaze behavior and the engagement in a secondary task. Background: In-depth accident analyses indicate that a lack of appropriate expectations for possible critical situations and visual distraction may be the major causes of rear-end crashes. Studies with FCW systems have shown that a warning alone was not enough for a driver to be able to avoid the accident. Thus, an additional braking intervention by such systems could be necessary. Method: In a driving simulator experiment, 30 drivers took part in a car-following scenario in an urban area. It was assumed that different lead car behaviors and environmental aspects would lead to different drivers' expectations of the future traffic situation. Driving with and without FCW+ was introduced as a between-subjects factor. Results: Driving with FCW+ resulted in significantly fewer accidents in critical situations. This result was achieved by the system's earlier reaction time as compared with that of drivers. The analysis of the gaze behavior showed that driving with the system did not lead to a stronger involvement in secondary tasks. Conclusion: The study supports the hypotheses about the importance of missing expectations for the occurrence of accidents. These accidents can be prevented by an FCW+ that brakes autonomously. Application: The results indicate that an autonomous braking intervention should be implemented in FCW systems to increase the effectiveness of these assistance systems.