E - Companion — “ Approximating Vehicle Dispatch Probabilities for Emergency

Two main streams of literature are relevant to the problem of considering server unavailability in emergency response systems. The first is that on the development of analytical models that allow for the calculation of measures related to server availability. The second is that related to location models for emergency service systems that incorporate such measures. Table A-1 summarizes the methods that will be discussed here in terms of the assumptions made about the four areas of the system outlined in the paper. Note that for the first three characteristics, the column heading is the characteristic and for each model we state the assumption made about that characteristic, but for the last characteristic (server cooperation) we focus on a specific aspect of the characteristic (server dependence) and only provide information about that aspect within the table. The reason for this is that all of the models incorporate some information about server cooperation, typically in the form of a “closest available ambulance” dispatch rule, and the main differences between the models in terms of this characteristic are in the way that they model the server dependence aspect. Additionally, we have attempted to list the models in order of increasing realism, although given the variety of assumptions, in some cases the order is admittedly subjective.