The objective of this research is to present a method for evaluating t
he performance of access control security systems, such as airport sec
urity operations. This requires the examination of security system arc
hitectures, which involve security technology devices and the algorith
ms that coordinate their operations. Dependence between device respons
es in multiple-device systems is a critical practical issue in assessi
ng the performance of such architectures, though no results on this pr
oblem have appeared in the literature. This paper presents a method fo
r evaluating when multiple-device security systems with overlapping ca
pabilities are cost-effective. This is achieved using a dependency str
ucture for security system devices to quantify how various technologie
s interact and to measure the impact of device dependence on system er
ror probabilities. A measure of device response dependence for a two-d
evice system is defined and its properties are explored, including bou
nds on the dependency measure. The effect of dependence on the system
Type I and Type II error probabilities is examined for the two-device
system. System performance is compared for independent vs. dependent d
evice responses and desirable dependence relationships are identified.
Results are also presented for a cascading sequence of devices. An ex
ample is presented to illustrate the results for the two-device system
. Implications of these results are discussed, such as how they can be
used to identify the optimal use of security devices and to determine
whether new technologies warrant investment.