Design and analysis of a two-stage security screening and inspection system

Security inspections are becoming a commonplace activity in locations ranging from airports to museums and shopping malls. Theses inspections can result in significant operational costs to a facility and to entry delays for the individuals being inspected. In this paper we focus specifically on passenger inspections at US airports. We consider a two-stage inspection system in which we are able to control the service rate of the first inspector. The relationship between the inspection service rate and accuracy is assumed described by a known speed and accuracy operating characteristic curve. Using a queuing model we derive the optimal design for the passenger security inspection operation at a given arrival rate, and also evaluate the utility of any investments in inspection rate improvement. The primary performance metric for the security inspection system is the average waiting time of the arriving entities or passengers. The optimal result specifies the number of inspectors at each stage, the service rate of the first inspector, and the total system cost. Numerical results with an example system are presented.