Management systems for unpaved roads are often viewed as unwarranted because of the low levels of traffic normally found on these roads. However, unpaved roads in many developed and developing countries represent the larger portion of mileage in the network. Even at the low cost of maintenance per mile of unpaved roads, the total costresulting from multiplying this value by the overall road mileage corresponds to a large financial outlay. Therefore, the efficient management of these roads is justified. Recognizing the need to optimize the blading and regraveling frequencies of unpaved roads, some agencies tried to develop methodologies for determining the appropriatemaintenance strategies. The procedures vary from road classification-based maintenance to economic analyses of alternative maintenance frequencies. However, the general approaches used in solving the maintenance problem are unsatisfactory as they either require restrictive assumptions or do not give closed-form solutions. This paper presents a dynamic optimization approach for determining the optimum blading frequency for an unpaved road using the principles of optimal control. The model is based on a procedure developed for setting overlay frequency and thickness for paved roads. The optimization equations are formulated for unpaved roads and applied to hypothetical cases. A sensitivity analysis is performed to evaluate the parameters in the model. The study indicates this approach is appropriate for determining optimal blading strategies for unpaved roads. However, further research is required to develop suitable deterioration and usercost functions and to include the frequency of regraveling. This paper appears in transportation research record no. 1252, Design, management, and operation of pavements.
Abstract