Abstract
Low luminance contrast occurring with fog or snow under photopic conditions creates extremely dangerous situations when driving, especially when following other vehicles. In these situations, detecting motion of the lead vehicle is greatly reduced due to low contrast sensitivity. In particular, the expansion information necessary for detecting potential collisions may be poorly integrated. We created a driving simulation framework to test alternative lighting configurations on snowplows to improve detection of approach in low luminance contrast situations, reducing the time to respond in a realistic, driving simulation study. We compared errors and reaction times in a simulated driving task over virtual 3D roadways in which participants judged whether the lead snowplow vehicle was approaching or withdrawing. We compared lighting that was similar to that used in current snowplows to ones in which vertical non-flashing bars were added to the outer edges of a snowplow and to a condition in which bright corners were added. We found a significant drop in response time to information for impending collision when non-flashing vertical bars positioned at the left and right sides of the vehicle were added to a baseline display that had only normal flashing lights. The average response time for the flashing condition was 1.96 seconds, while the reaction time for the vertical bar condition was 1.84 seconds. We also found that when the lights on the corners were added to the vertical bars average performance again improved to 1.79 seconds. Ability to detect information for approach under dense fog or snowing conditions can be substantially improved if lighting on the lead vehicle is altered to optimize the light positioning and orientation. These transformations raise the optical expansion information over threshold for subjects in a driving simulation study. Other lighting designs may be even more effective in improving the safety of drivers.