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.
Group for Research in Decision Analysis