Abstract
Previous research studies provide contradictory results in investigating driving speeds under foggy conditions. Therefore, a series of three simulator studies were conducted to examine the impact of fog on driving speed. In all of the studies, 12 participants drove along continuously-curvy roads with a 55-mph speed limit under 6 fog conditions (visibility distances of 496, 179, 70, 31, 18 & 6m.) In Study 1, drivers were encouraged to maintain a speed between 50 and 60 mph and were able to use the speedometer. The participants drove a mean speed of 55 mph for all conditions except the foggiest (6m) where speed dropped to 51 mph. In the remaining two studies, participants were encouraged to drive at a self-chosen “comfortable” speed. The participants could use the speedometer in Study 2, but not in Study 3. In Study 2, the drivers' speed was at or near the speed limit until the foggiest two conditions (18 & 6m), when mean speeds decreased to 48 and 38 mph, respectively. In Study 3, the mean speed was 60 mph or above for all but the foggiest two conditions, when speeds decreased to 56 and 44 mph, respectively.
This work was supported by the National Science Foundation and the Department of Defense ASSURE Program under Grant No. SES-0353698.