Concepts and Applications of Backup Coverage

Backup coverage, the second coverage of a demand node, is suggested as a decision criterion in modelling the location of emergency services on a network. The efficient handling of stochastic demand by vehicles which can respond to only one call at a time may require backup coverage in areas of high demand as a means to maintain a more uniform level of service. This new criterion is applied in the context of the classic covering models, the Location Set Covering Problem and the Maximal Covering Location Problem. First coverage as defined in these models is traded off against backup coverage in the present work. Other efforts which incorporate additional levels of coverage are reviewed. We also show how to extend these models to third as well as subsequent coverage. Based on an example problem we show that significant levels of backup coverage may possibly be provided within a system without substantial loss of first coverage.