Task 3 of the Enhanced Rear Lighting and Signaling project was directed toward refinement and initial field testing of two “imminent-warning” signals. These signals are intended to direct the following driver’s visual glance to the lead vehicle as it brakes rapidly to a stop. The signals can also be used to warn of an impending rear-end crash. Task 3 consisted of a preliminary experiment and a main experiment. In the preliminary experiment, modifications to an alternating pair of lamps were tested in a static situation using human factors experts. Results of the experiment indicated use of greater drive voltage and kick voltage improved the attention-getting capability of the alternating pair. Results also showed that an alternating frequency of 4.0 Hz was optimal. Previously, the TCL (traffic clearing lamp) had been selected as the most promising imminent-warning signal. Consequently, in the main experiment, the TCL and the IAP (improved alternating pair) were compared to ordinary rear lighting. The main experiment was conducted on the Virginia Smart Road in Blacksburg, Virginia, using a surrogate vehicle (drawn by a lead vehicle) containing conventional lighting and the two new, imminent-warning lighting configurations. Seventy-two ordinary drivers, split into three groups, participated. Driver subjects were purposely distracted by in-vehicle tasks as the lead (surrogate) vehicle underwent hard braking. Responses were compared for the conventional and two enhanced lighting groups. Results showed improvements in brake activation times of 0.25 to 0.35 seconds, corresponding to 15 to 30 feet (4.6 to 9.1 m) of additional stopping distance for the enhanced lighting. The TCL was just slightly better than the IAP. The results also demonstrate a learning effect between the first and second exposures, with braking performance improving with second exposure. Other measures suggested that the eyes are drawn to the forward view more quickly with the enhanced lighting. This report fully describes the experiments and results. It then recommends additional refinements and fleet testing because of the promise shown by the results thus far. (Author/publisher)
Samenvatting