Improving ambulance coverage through the use of alternative return routes during vehicles' repositioning

Emergency Medical Services organisations devote considerable effort to reducing response times and maximising the coverage provided to the population. When an ambulance completes a service, it undergoes a repositioning process which involves selecting a base to wait for the next service assignment. Although repositioning can increase system coverage by choosing a new waiting site, practical considerations – such as team working habits and existing legislation – often require ambulances to return to their home bases. This paper proposes a new repositioning strategy: ambulances return to their home base but following alternative routes rather than the fastest or most direct one. This allows them to increase overall coverage during the journey, since ambulances en route to their base can be reassigned to incoming emergencies. To the best of our knowledge, this is the first study to formally conceptualise and empirically evaluate the potential of this strategy. Experiments on 600 instances inspired by the real cityscape of Valencia, Spain, demonstrate that the proposed strategy outperforms not only the policy of returning to the usual base via the quickest route, but also the more sophisticated strategy that allows ambulances to be repositioned to other bases.