Flying capacities, optimal fleet sizes, break-even flight charges for helicopter medical emergency service

We analyzed transportation issues involved in supplying helicopter emergency medical service (HEMS)--specifically, how many calls can be served by an HEMS program, the optimal number of helicopters in a program, and the flight charges required to "break-even". We developed a simulation model to capture the HEMS stochastic operating process and used a multiattribute expected utility (MAEU) model to evaluate HEMS program performance along the dimensions of financial, publicity and medical benefits.;Based on the results of the simulation model, we derived functions that represent the mean fraction of calls served versus demand. We parameterized these performance functions according to four "operating variables"--external effects, average service time, demand seasonal and daily peaking characteristics--and proposed an interpolation method to expand the results to general HEMS programs. Sensitivity analysis revealed that the external effects (combination of weather, helicopter unexpected maintenance, and request cancellations) has the biggest impact on the number of calls served.;MAEU analysis of the optimal number of helicopters in the fleet suggested that a desirable HEMS operation could start at a demand level of 700 requests per year and expand at 1300 requests per year. The demand levels would change if there were competing service in the area or if the medical and publicity attributes were not considered. Sensitivity analysis indicated that the flight charge, fixed costs, and utility scaling parameters are the most influential parameters in the analysis of optimal fleet size.;MEAU analysis of the "break-even" flight charge revealed that with the 1992 national average flight charge (...