An analytical approach to determining if roadway lighting is warranted was developed through the National Cooperative Highway Research Program (NCHRP Report 152) using four comprehensive evaluation forms. The four forms relate to non-controlled — access roadways, intersections, freeways, and interchanges, and are presented in Figs. 7.61, 7.62, 7.63, and 7.64, respectively [10]. The forms are used by multiplying the rating of a characteristic by the difference in its unlighted and lighted weight to obtain a quantitative measure of the effect of that characteristic on driver visual information needs. After all the characteristics are rated, the scores are summed to obtain an overall measure of driver information needs.
There is an established “minimum warranting condition” of a given number of points for each of the four forms. The exact number of points is determined by assuming a rating of 3 for each of the characteristics. It should be emphasized that the minimum warranting condition is not firm, but merely a starting point. This method is flexible and permits modifications to fit local needs. This procedure also provides a method for administrators or planners to prioritize lighting projects by using objective standards to determine where lighting would be most beneficial.
