Today as I was travelling down the road, shortly I got off the interstate, I came to an area where the road was being repaved. Along with all the other vehicles that were around there was one work truck parked on the shoulder of the road. On the back of this work truck was an open yellow box that looked to be made of plastic. On the front of this box was a big caution sticker with “Radioactive” and the radiation symbol on it. Does anyone have any idea what this box might be for or why they might need something radioactive for paving the road? The box was about the size of your average cooler you may take camping or to the beach.
Probably from asphalt testing. There is a machine that allows you to test asphalt without pulling a core (the usual way).
It more than likely was a cooler and the sticker just an attempt at humour
I asked my brother who is an expert in all things cars including roads. First words out of his mouth was “To keep flies away.” So there you go. From someone I consider an expert.
robby, I think you and bernse are right. I do recall two guys in front of the truck (in the lane that traffic wasn’t using) with some yellow, square device that was laying on the asphalt. They were standing over it like they were taking some kind of measurement.
Thanks for all the replies, everyone. 
Another possibility is that it was a nuclear density gauge. Getting good compaction of the asphalt is critical to paving operations. (The steel drum and rubber tired rollers work on this.)
In Minnesota we use nuclear density meters but I’ve never seen a nuclear asphalt content gauge used. (Thanks robby for the link.)