Port-of-entry inspection: Sensor deployment policy optimization

This paper considers the problem of container inspection at a port-of-entry. Containers are inspected through a specific sequence to detect the presence of nuclear materials, biological and chemical agents, and other illegal shipments. The threshold levels of sensors at inspection stations of the port-of-entry affect the probabilities of incorrectly accepting or rejecting a container. In this paper, we present several optimization approaches for determining the optimum sensor threshold levels, while considering misclassification errors, total cost of inspection, and budget constraints. In contrast to previous work which determines threshold levels and sequence separately, we consider an integrated system and determine them simultaneously. Examples applying the approaches in different sensor arrangements are demonstrated. Note to Practitioners-Increased emphasis on container inspection at ports-of-entry prompted researchers to investigate methodologies that help practitioners in operating such inspection systems in order to reduce both the risk of accepting "undesired containers" as well as the cost of inspection. The threshold levels of the sensors can be adjusted by changing, for example, the power level of the X-ray machine or the count level of the sensors in order to make appropriate decisions. This paper provides methodologies for determining the optimum threshold levels of sensors and order of inspection that minimize the overall cost of the system. An approach for obtaining these values under budget and risk constraints is also included in this paper.