In 1998, nearly 30% of all fatal accidents involving large trucks occurred during hours of darkness, according to the Federal Motor Carrier Safety Administration's Large Truck Crash Profile: The 1998 National Picture (27). In about 1.5% of crashes involving large trucks, police reported that drivers visibly appeared to be fatigued or very tired (27). More than 7% of single-vehicle fatal truck accidents were reported as having driver drowsiness or sleeping as a related factor (27). The National Highway Safety Administration (NHSTA) reports that 56,000 automobile accidents per year are caused by drivers falling asleep at the wheel. According to the 1990 World Almanac (23), each accident involving a fatality or very serious injury results in a cost of nearly $1.5 million, simply accounting for wage losses, medical expenses and insurance administration.

Humans are a diurnal species, programmed to be awake during the day and asleep at night (30). Therefore, it is not surprising that sleepiness plays an important role in vehicles accidents. The most common preventive action taken by sleepy drivers is to stop driving, change the environment in the vehicle by opening the windows or turning on a loud radio, or consume caffeinated products. Although the preferred preventive action is to stop driving, it is known that this course of action does not always happen due to work demand. In principle, light can be used as a non-pharmacological treatment for increasing alertness at night and thereby possibly reducing sleep-related traffic accidents. Recent research has begun to illustrate the many ways that light and lighting systems affect humans in terms of circadian photobiology, including the characteristics of light necessary to regulate the circadian system.

While further research is no doubt necessary before lighting criteria for the circadian system will have equal weight as visual criteria in the design of transportation lighting systems, it is becoming increasingly evident that lighting practice will eventually have to consider circadian photobiology. One major barrier before circadian photobiology can be considered in transportation application is how light for the circadian system can be introduced without significantly increasing disability glare and reducing night-time visual performance.

The goal of this proposal is to investigate how disability glare and visual performance of night-time driving will be affected by a lighting system that is designed to increase night-time alertness. If funding is available, we propose to also determine for how long the alerting effects of night-time light remains after light stimulus offset, which has significance if “light showers” are introduced in rest-stops facilities instead of inside truck cabins.