Optimal Allocation of Emergency Response Service Units to Cover Critical Infrastructures with Time-Dependent Service Demand and Travel Time

Abstract

Optimal deployment of limited emergency response service (ERS) units in a metropolitan area is of interest to public agencies. The limited emergency units not only have to respond to the demand for service by citizens and businesses but also have to cover critical infrastructures (CIs). The paper formulates an optimization model to allocate different types of ERS units among their candidate base stations. The allocation of units must ensure maximum coverage to CIs, subject to the capacities of the base stations, service standard in terms of time to reach the CIs, and the availability of the ERS units (when there are other competing demands for services). Unlike past models, the modeling approach here accounts for the fluctuation of travel time and demand frequency at different time periods of a typical day. The applicability of the model has been demonstrated in a case study in the city of El Paso, Texas, which allocates 45 firefighting units and 23 ambulances among 34 active fire stations to cover 138 critical transportation infrastructures, hospitals, and schools.