In an era of continuous growth in mobility and demand for transportation, safety is an issue of major social concern and an area of extensive research and work by practitioners and academics. Emergency response services are very important in handling and minimizing the impacts of traffic accidents and for saving human lives. In this paper, we develop an efficient emergency response plan for responding to traffic accidents; the objective is to strategically deploy emergency response vehicles in a large urban transportation network. We combine a location model with a genetic algorithm and guide location decisions through accident metrics such as accident frequencies and severities at different parts of the network. We demonstrate the usefulness and applicability of this approach by planning for a real-world case study in the city of Thessaloniki, Greece.