Operational control of the transportation of hazardous materials: an assessment of alternative decision models

Commercially available tracking systems based on advanced communications and computing technology allow a dispatcher of hazardous material transports to monitor the movement of vehicles on a transportation network in real time. When unexpected events occur, a dispatcher working with this new technology can identify the regions surrounding the transportation network that are affected by these events and determine safe and cost-effective routes for the vehicles that plan to drive through those regions. Four decision models for rerouting hazardous material vehicles in real-time have been assessed in an experimental setting. The first model supports a dispatcher in finding alternative routes (visually), while the second model adds to the display, for each vehicle, an alternative route based on a conservative heuristic. The other two models are based on an ordinal preference and a numerical utility structure to support the dispatcher in determining the impact of the events on transportation safety and costs. The models were embedded into four decision support systems that use multimedia technology to simulate the dispatchers workstations. These systems were then used in an experiment at the dispatching school in Wil, Switzerland, with 32 experienced dispatchers and truck drivers to assess efficiency and accuracy of the four models. The results show that assessing risks and costs with the ordinal preference structure, prior to making routing decisions, is significantly more efficient and accurate than searching directly for new routes. Using a numerical scale for safety and cost assessment was disliked by the subjects and led to inferior results.