INVESTIGATION OF THE RELATIVE COST-EFFECTIVENESS OF PAVED SHOULDERS ON VARIOUS TYPES OF PRIMARY HIGHWAYS IN NORTH CAROLINA FOR THE PURPOSE OF ESTABLISHING PRIORITY

This investigation compares accident rates for highways having paved shoulders with accident rates for similar highways having only grass or sod shoulders. The significantly lower accident rates on paved shoulder highways are utilized to develop numerical values for the dollar amount of accident cost reduction directly attributable to the presence of a paved shoulder. Treating the dollars of accident cost reductions as benefits, an investment return analysis is performed, relating the benefits to paved shoulder construction costs. The study utilized an analysis of covariance to identify the highway classification variables sensitive to accident rate differences between highway sections with paved and unpaved shoulders. The study concludes that a range of paved shoulder construction costs can be economically justified on the basis of accident cost reductions for two-lane, two-way rural primary highways with average daily traffic volumes greater than 2,000 vehicles per day. The results of this investigation are derived from data in which the paved shoulders were predominantly 3 to 4 feet wide, and were "added on" to an existing highway with little or no change in alignment. Paved shoulder construction costs did not exceed $14,000 per highway mile. /Author/