About the research
During winter road maintenance operations, the Iowa Department of Transportation (DOT) is responsible for servicing 24,000 lane miles of roadways, including Interstates, US highways, and Iowa roads. This project focused on operations for District 3, located in northwest Iowa, which services about 4,000 lane miles from 20 depots.
Two optimization problems were solved to determine the optimal snowplow routes in this district. The first problem was to design winter maintenance truck routes for single depots under the district’s current responsibility maps. The second problem was to design routes for multiple depots with intermediate facilities, with the service boundaries among the depots able to be redesigned. Both optimization problems were solved as capacitated arc routing problems (CARPs) using a memetic algorithm (MA) and considering the constraints of road segment service cycle time, heterogeneous vehicle capacities, fleet size, road-vehicle dependency, and work duration.
The results from solving the single-depot optimization problem show a 13.2% reduction in deadhead distance compared to current operations. The deadhead savings could be even larger because while the optimized routes strictly satisfy all constraints, the current operations might not. For the multiple-depot optimization problem, due to the network structure and current depot locations, the difference between the optimized routes based on a multiple-depot configuration and those based on a single-depot configuration is insignificant.