BOOKS OF RtfiDIfGS - PAHO/WHO

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REVet.
¡T AL
Act of 1973. The menaning of an "adequlate nul>cier of emergency
vehicles, called for in the legislatioan. is interpreted in the regulations
as a number suifficient tlhat 95 percent of relquests for assistance can be
met within 30 minutes in rural areas and 10 minutcr. in urban areas.
To the location analyst. tihe framers of the regulations lor emergency
services appear ao he among the most articiulate of decision makers.
for their specificatiolis of elfectiveness mnicsures are cear, concise
mathematical entities. Tihe analyst is seldom fortunate enough to
encounter such precise problem statemcnts.
The coincidence of viewpoints of tie frainers of t¡he rcgulations
arid the autihors of the naxinial covcring model suggests, correctly.
that this model was structured to meet real needs. In fact, the origin
of thle model lay in a 1970 report of the Carnegie Comnission on
Higher Education (42]. That report called for establishment ol 55
t
lieaith i are teiters acroís the natiol, loatced iii stlch a way that 95
percent of the populatio.! was within :an hoiir', drive of a faciliy.
IlThe numinbers aside. this concise stat,:imtciit sparked the lcvelopinicivt
of the maximal covering problem by Chur(hl and ReVelle [41] out ol
lthe location set cove'ring problem.
The maximal covering inoxlel ullers adtlitiona.sl informination beyond
that requested by the EMS regulations. As discussed previously
in connection wiíth Fig. 1 (jp. 137), tihe maximal covcring model can
indicate noi only the n numbe r and locations of vchicles requuired for
95 percent of responses to o(xcur within 3S minites. but also the nunmhkr
arul !ocatiois needed for any coverag;e level one wislies. allowing
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