Groupe d’études et de recherche en analyse des décisions

Descriptive and Prescriptive Models of Ambulance Service Operations

Armann Ingolfsson

We outline different models that have been proposed for performance evaluation of ambulance systems as well as models for optimal location of ambulances. We describe a specific optimization model that minimizes the number of ambulances needed to provide a specified service level. The model measures service level as the fraction of calls reached within a given time standard and considers response time to be composed of a random delay (prior to travel to the scene) plus a random travel time. Pre-travel delays at the dispatch and activation stages can be significant, and models that do not include such delays can severely overestimate the possible service level for a given number of ambulances and underestimate the number of ambulances needed to provide a specified service level. We illustrate the use of the model using real data from Edmonton.