SCREENING METHODOLOGY FOR NEEDS OF ROADWAY LIGHTING

Screening methods of the American Association of State Highway and Transportation Officials (AASHTO) and the National Cooperative Highway Research Program (NCHRP) that assess the local potential for fixed roadway lighting to decrease nighttime crashes have not been updated since the 1970s. The methods dilute the influence of important factors, are inadequate for locations where crash histories are unavailable, and lack a traceable theoretical foundation. This report evolves and complements existing screening methods in order to develop an updated method to aid engineers and planners in the screening of needs for fixed roadway lighting. Development of the method adopts principles of risk assessment and management that have been previously applied in diverse disciplines. The existing screening methods, which provide a basis for the developed screening method, are strengthened by the development of a theoretical foundation in benefit-cost analysis. The developed method has two phases. In the first phase, an exposure assessment is developed to describe individual and population exposures to crashes. Needs are compared by night-to-day crash rates, measured directly or estimated indirectly, and traffic volumes. Outcomes of exposure assessment are identified based on potential crash reduction and costs of available lighting technologies. The second phase builds on selected concepts of the NCHRP method. In testing of the two-phase method, night crash histories for over eighty unlighted sections in three regions of Virginia are collected and studied. Example applications of the method to individual locations are demonstrated. The recommendations are as follows: (i) highway agencies should consider designating funds for lighting and visibility enhancement using the developed screening method in resource allocation; (ii) agencies should provide training and continuing education in the developed screening method, and emphasize the unity of principles of risk assessment and management across highway safety issues; (iii) through a testing phase, agencies should consider replacing the AASHTO and NCHRP methods with the developed method; (iv) agencies should perform regional data analysis and screening of unlighted locations on an annual basis; and (v) agencies should incorporate the method in holistic lighting master plans.