The timecourse of driver visual attention in naturalistic driving with Adaptive Cruise Control and Forward Collision Warning

Adaptive Cruise Control (ACC) and Forward Collision Warning (FCW) have been shown to have a positive effect on safety-related measures despite a general increase in secondary task involvement. To understand this effect, this study examined the relationship between drivers glance locations and ACC hard braking or FCW events when ACC is active. The study analyzed naturalistic driving on motorways where the car remained in the same lane. Four subsets of driving segments were included: ACC braking (peak deceleration ≥ 3 m/s2), FCW+ACC (driving with ACC when a forward collision warning was issued) ACC maintaining speed, and Driver braking without ACC or FCW. The results indicate that although drivers do take their eyes off path more when using ACC, this conclusion seems to be valid only in non-critical (baseline-similar) situations. Drivers showed a steady increase in %EyesOnPath well before critical situations, resulting in 95% EyesOnPath both at the onset of ACC braking and at the onset of driver braking, and 98% when FCW were issued. At braking onset, headway was significantly longer when ACC braked compared to when the driver braked