Trends in Driver Response to Forward Collision Warning and the Making of an Effective Alerting Strategy

This paper compares the results from three human factors studies conducted in a motion-based simulator in 2008, 2014 and 2023, to highlight the trends in driver's response to Forward Collision Warning (FCW). The studies were motivated by the goal to develop an effective HMI (Human-Machine Interface) strategy that enables the required driver's response to FCW while minimizing the level of annoyance of the feature. All three studies evaluated driver response to a baseline-FCW and no-FCW conditions. Additionally, the 2023 study included two modified FCW chime variants: a softer FCW chime and a fading FCW chime. Sixteen (16) participants, balanced for gender and age, were tested for each group in all iterations of the studies. The participants drove in a high-fidelity simulator with a visual distraction task (number reading). After driving 15 minutes in a nighttime rural highway environment, a surprise forward collision threat arose during the distraction task. The response times from the FCW event were recorded and analyzed. The results indicated no statistically significant difference in driver response times between the baseline-FCW condition and the two new variants of the 2023 study. However, a trend of longer driver response times was seen when comparing the results from 2023 study to previous studies. First, the median response times for the baseline-FCW group increased from 2008 to 2023 by about 0.25s. Furthermore, in the 2008 study, a few cautious drivers in the control group had reacted even before the distraction task had finished. However, in the 2023 study, all participants only reacted after the distraction task had finished. Finally, there was a statistically significant difference between the 2023 fading-FCW chime variant and the 2008 baseline-FCW. All of this indicates that drivers are likely becoming more complacent to warnings and are less situationally aware due to distraction from non-driving activities.