[en] This report compares several types of special nuclear material monitors used to search motor vehicles at area exit gates. These monitors use either portable, hand-held instruments or stationary radiation detection instruments. Stationary monitors have a detector portal or a detector array located in the roadbed at a vehicle exit. Static measurements and operational evaluation provide a performance comparison of three types of monitors: hand-held instruments, vehicle portals, and a high-sensitivity roadbed monitor. Still higher sensitivity is possible by placing detectors overhead as well as in the roadbed; such a combined monitor does not yet exist, but the report estimates its performance. The cost for a combined monitor increases significantly when both a canopy and a roadbed detector pit are constructed; however, the performance of the combined monitor exceeds that obtained with other monitor configurations. 27 figures, 6 tables