| Shipping hazardous material (hazmat) places the public at risk. People who live or work near roads commonly traveled by hazmat trucks endure the greatest risk. Careful selection of roads used for a hazmat shipment can reduce the population at risk. On the other hand, a least time route will often consist of urban interstate, thus placing many people in harms way. Route selection is therefore the process of resolving the conflict between population at risk and efficiency considerations. To assist in resolving this conflict an easy to use decision support system (DSS) is developed.; The problem configuration chosen for generating a route is a constrained shortest path. The origin to destination travel time is minimized while limiting the sums of other link attributes. These attributes include distance, accident probability, expected consequence and total population at risk. Except for distance, the link attributes can be time dependent; therefore, any solution method must be capable of route selection utilizing temporal attributes.; Two heuristics are developed to produce an origin to destination path. One method utilizes the Euclidean distance from a candidate node to the destination. The second method uses Lagrangian relaxation. When road costs are time dependent, a subpath of an optimal path may not be optimal. A truck may stop and wait for temporal costs to fall off before proceeding. Extensive computational testing is performed on data sets with either non-temporal or temporal road attributes.; The DSS permits a user to input limits on the attribute sums and generate a path. This allows an operator to quickly define the efficient frontier. The DSS uses a realistic road network with about 57,000 intersections. A user is able to remove intersections from path consideration to direct the generated path and reduce computer runtime. Custom software is used to construct the DSS. This allows greater control over the DSS's components and, it can function on a desktop personal computer without purchasing GIS software. |
