A simulation model for evaluation of a real-time emergency medical service vehicle response system that uses real-time travel time information and that assists the emergency vehicle dispatchers in assigning response vehicles and guiding those vehicles through noncongested routes is developed. Different response strategies are evaluated with this simulation model. These include the first-called, first-served strategy, the nearest-origin assignment strategy, and the flexible assignment strategy that uses real-time travel time information to assign and dispatch response vehicles. Different assumptions and conditions are used to test the sensitivity of the flexible assignment strategy.