An X-ray cargo inspection system and method. A lead-in conveyor on a first trailer receives a cargo container for inspection. An inspection module disposed on a second trailer then scans the cargo container with penetrating radiation, detects penetrating radiation that has interacted with the cargo container, and produces an inspection signal. An exit conveyor disposed on a third trailer projects the cargo container following scanning. The inspection module may contain transmission or scatter detectors, or both. Multiple lead-in conveyors may serve to load additional cargo containers for subsequent scanning by the inspection module.