Lucky (fool).

[viperman]

the signal arm was wedged behind the back of the cab

From this sentence, it sounds like either a semi or a pickup truck, hard to tell exactly. My first impression was that its a pickup truck, and that he couldn't move from where he was because the arm had come down and wedged in place between the cab and bed of the truck, so proceeded to exit the truck. I may be 100% wrong, but thats the way I read it at first