Why the closest ambulance cannot be dispatched in an urban emergency medical services system

Response time performance is related to increased survival for a relatively small group of patients with critical emergencies. Effectively utilizing current resources is a challenge for all emergency medical services (EMS) systems for reasons of cost-effectiveness and safety.

The objective of this study was to identify opportunities for improving ambulance response-time performance in an urban EMS system using fixed deployment.

This was a qualitative and quantitative case study which consisted of structured interviews with policy makers, managers, and workers in a fire department EMS division, as well as analysis of dispatch data and observation of dispatch operations.

The current computer-aided dispatch (CAD) system does not identify the closest ambulance to the emergency, and therefore, dispatchers must guess which unit is closer when units are not within their stations or "first due" areas. There is no means to track how often dispatchers guess correctly or how often the closest ambulance actually is dispatched to the emergency. Temporal and geographic patterns were identified. Opportunities also were identified to improve response time performance through the use of dynamic deployment and peak-load staffing.

The results suggest that there were opportunities for improving ambulance response times by implementing strategies such as peak-load staffing and dynamic deployment. However, the most important improvement would be the implementation of a policy to send the closest ambulance to the emergency. More research is needed to identify how prevalent the failure to send the closest ambulance is within EMS systems that use fixed-deployment response strategies and computer-aided dispatch systems that are incapable of tracking unit locations outside of their stations.