You never know
There are a small number of OTR units devoted to really sensitive cargo. It's been done this way for years, it's effective, relatively cheap and safe.
Ship the mundane hardware one way, the dangerous stuff in separate components to minimize hazards, and the classified components by secure mode.
What's in that truck you just passed? Most of the time just routine goods, but, one out of a couple of thousand or so............it isn't the big black one with all the guards and escort, it's the un, or mismmarked unit on I-20