For a number of years, Idaho's pavement policy has included f11ll-wi< lth p:: ivP. mP. nt with shoulders paved the same thickness as the roadway. Overall widths have conformed generally to AASHTO standards. These standards were accepted in the absence of a formal analysis of local conditions suitable for establishing width criteria.

This study was undertaken to analyze local data and to obtain relationships among pavement width, construction and maintenance costs, and accident costs for rural two-iane highways. The invesLigaLiu11 included two major phases: first, a statistical analysis of accident records to investigate the effects of width and other factors and, second, using accident trends determined from the first part of the study, economic analyses to evaluate the overall economic effects of different pavement widths in various average daily traffic ranges.