Ambulance economics

Background Ambulance services produce a large quantity of data, which can y ield valuable summary statistics. For strategic planning purposes, an econo mic framework is proposed, and the following four resource allocation quest ions are answered, using data from the Surrey Ambulance Service: (1) To sat isfy government response time targets, how many additional ambulances will be required, ceteris paribus? (2) To minimize average response time (r*) wi th given resources, how should ambulances be rostered temporally? (3) Which innovations are worth undertaking? (4) How would an increase in demand aff ect r*? Methods The 'Ambulance Response Curve' - the relation between response time and the number of available but not-in-use ambulances - is used to estimat e how much r* will be reduced by deploying an additional ambulance. Estimat ing the marginal cost of an ambulance allows us to estimate the opportunity cost of each second of response time, and to compare the cost of three 'in novations' with that of increasing resources. The time savings of adding an extra ambulance at each of the 168 h of the week are examined. Results in 1997-1998, r* was 8 min 52 s. An additional ambulance reduces r* by 8.9 s. Each reduction of 1 s in r* costs pound 28 000 per year. Fourtee n additional ambulances are required to meet response time targets if the 8 .9 s reduction per ambulance is maintained. r* reduces by 4.6 s when ambula nces are shifted from early mornings to Saturday evenings. Activation time reduces by 38 s when crews sit in their ambulances. A 1 min decrease in ove rall call time decreases r* by 1.1 s. Answering only 10 per cent of all cal ls reduces r* by 63 s. An increase of demand of 10 per cent increases r* by 7.8 s. Conclusions Ambulance services will be better able to determine which innov ations are worth undertaking. Policy makers will be better placed to determ ine funding levels to achieve response rime targets.