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.