While many who travel in airports are rushing to catch a flight, we take for granted the technology that keeps us safe -- the baggage scanner. An airport security screener’s ability to find weapons or explosives hidden in luggage can be affected by the visual complexity of the X-ray image. Visual complexity is difficult to measure, and the best metric of complexity had been a subjective, five-point “clutter” scale with little validity or reliability. The Transportation Security Administration (TSA) asked Battelle to create an objective, quantitative measure of visual complexity so that its effects on screening performance could be studied more rigorously.
Our scientific evidence suggests that the number of items in an image affects a screener’s ability to detect a target item; however, a computer cannot count the items using current image processing technology available in X-ray screening. With expert knowledge in human perception and image processing, Battelle scientists identified 40 potential visual complexity metrics. They calculated these metrics for hundreds of X-ray images containing threat objects, such as guns, knives, and improvised explosive devices (IEDs), for which TSA screener threat identification performance measures existed.
Using multivariate statistics, Battelle identified a set of metrics, which accounted for over 70% of correct and incorrect screener decisions. When the visual complexity metrics are calculated for actual baggage, they correlate highly with the number of items actually in the baggage, thus providing the TSA with information about baggage that could not be obtained previously.
Battelle's innovative research in applying human engineering to the process of baggage screening is helping the Transportation Security Administration pioneer new ways to improve the speed and accuracy of their screening processes.