very conspicuous vehicle,
What is so conspicuous about another 18 wheeler going down the road? Most folks have NO idea what the placards mean. THAT would be the easiest part to do...hijacking the truck and possibly doing away with the driver would be the Murphy Law part.
I was driving in Wyoming one time following a semi that had a certain placard. this was before cell phones and when Cb radios were a must. Got the driver on the radio and asked about her placard....turns out she was carrying spent nuclear fuel rods to a dump somewhere..........just a plain truck going down the road. Ammo trucks today would be as non-descript