When Should Brake Lights Be Activated During Regenerative Braking in Electric Vehicle?

Electric vehicles’s expansion raises concerns over brake light activation during regenerative braking. This study investigated how regenerative braking deceleration without brake light activation affects drivers’ driving behaviors and subjective workload. A within-subject driving simulator experiment was conducted with 28 licensed drivers under four regenerative braking deceleration levels (0.7, 0.9, 1.1, and 1.3 m/s2) within the current optional brake light activation range. Significant changes in minimum TTC and standard deviation of TTC first emerged between the 0.7 and 0.9 m/s2 conditions. Reaction Time and Brake Force differed significantly between the 0.7 and 1.1 m/s2 conditions, whereas Brake Count differed only between the 1.3 and the 0.7 and 0.9 m/s2 conditions. Subjective driving workload differed only between the 0.9 and 1.3 m/s2 conditions. These findings suggest that TTC-based safety measures were more sensitive than behavioral and subjective measures, identifying 0.9 m/s2 as an empirical candidate for evaluation of brake light activation criteria.