OPTIMAL HIGHWAY DURABILITY

An investigation is reported which found that in order to minimize discounted lifetime costs, typical urban interstate highways should be designed with thicker pavements lasting much longer between repavings. Also, existing roads have marginal pavement-wear costs that are quite high; optimal high-volume urban interstates would not. It is noted that the need for marginal-cost taxation, and the accompanying diversion of trucking industry revenues, would be virtually eliminated on a large portion of the nation's highway network if the highways were built to optimal standards. In this study, the standard model of optimal highway pricing and investment was reformulated to include highway durability as a long-run decision variable. The resulting pricing rule includes both a congestion charge related to scarce capacity, and a heavy-vehicle charge related to scarce durability. Expressions are derived for marginal-cost user charges, optimal capacity, optimal durability, and long-run marginal pavement-wear cost. An examination was then made of those parts of the model related to durability.