A maximum expected covering location model with two types of servers

Designing emergency medical service systems that improve patient outcomes is a problem of national concern. This paper introduces the Maximum Expected Coverage Location Problem with Two Types of Servers (MEXCLP2) for determining how to optimally locate and use medical units (such as ambulances) in order to improve patient survivability and to provide insight into how to optimally coordinate multiple types of medical units. In MEXCLP2, there are two types of servers (medical units), and there are dependencies between the types of servers and between servers of the same type. A Hypercube queuing model is developed to quantify these dependencies when servicing multiple types of customers (patients). MEXCLP2 is formulated as an integer programming model, and the results of the Hypercube model provide its input parameters. MEXCLP2 is applied to emergency medical service systems with two types of medical units (ambulances and non-transport vehicles). Results are illustrated using real-world data collected from Hanover County, Virginia.