In a previous experiment it was shown that fog considerably increased the estimated distance of vehicle when only the rear lights of these vehicles were visible. Distance perception was even more impaired when there was only one and not two fog-lights (both configurations comply to European regulations). The aim of the present study was to test nine rear fog-light configurations so as to examine the influence of width between fog-lights (135, 105 and 75cm) and height (90, 65 and 50cm above the ground) on the perception of vehicle distance. The experiment was conducted in a fog chamber in night-time conditions. Light configurations were presented at 5 different distances varying from 8 to 28 m. The subjects (N=20) were asked to give verbal reports on the distance of the simulated vehicle. The results revealed that in maximal fog-light width conditions, distance overestimation was reduced. The height of the lights did not influence the mean estimated distance, but an average ("standard") height resulted in more consistent estimates. None of the nine configurations was able to completely eliminate distance overestimation in fog. Based on these results we recommend improved regulations and, more particularly, standardisation for the design of rear fog-lights. (A)
Abstract