The project was undertaken to determine whether variation in the lighting of freeways leads to a variation in the number of nighttime accidents and if so, to what extent. The study found significant indications that increased freeway lighting makes a difference in the frequency of a variety of distinct accident types; increased lighting was not found to reduce total accident rates. The analysis was performed using stepwise multiple regression techniques. An analysis was conducted of the Interstate System Accident Research (ISAR-2) data base for information or implications useful in achieving study objectives. Factors found to influence selected categories of accident frequencies were traffic volume, year, interchange type, location and lighting. Illumination was found significant for only two of seven accident categories. The number of lights active at an interchange was found to influence two categories. Models were developed for planning purposes to assist highway design engineers determine predicted nighttime accident frequencies at various levels of lighting based upon expected nighttime traffic volumes, location and geometry of interchanges.
Samenvatting