A near-optimal solution to the rural road-bridge rehabilitation problem

Abstract

In this research a model is developed to aid decision making in the allocation of limited funds in the improvement of a large-scale, rural road-bridge transportation system. After applying a geographic decomposition scheme on the original network to divide the system into fairly independent local units (subnetworks), the optimization procedure identifies simultaneously the bridges which need to be replaced and the road sections which need rehabilitation without violating the budget conditions for a given period of the planning horizon. The road-bridge rehabilitation model is formulated as a mixed, non-linear programming problem with linear constraints. For a given set of replaced bridges, the original problem is reduced to a continuous non-linear programming problem which can be further decomposed into a traffic assignment problem and a road rehabilitation budget allocation problem. The solution methodology includes a tree search for integer variables and an iterative procedure between the traffic assignment problem and the road rehabilitation budget allocation problem. The proposed solution methodology is applied to the transportation network of Hansford County, Texas.