Odd.
I shipped Radioactive Waste from 1986 to 2021 and every shipment had a RADIOACTIVE placard of some kind on tractor and trailer.
The only thing I can think of that might go down the road 'Incognito' that might be radioactive would be nuclear warheads. You definitely have to have a spotless record (of all kinds) to haul those loads.
And most radwaste that goes down the road from power plant is unmistakable because it is in a cask. A spent fuel cask is really unmistakable. See the video in post 15.
By the way we did have a truck driver for one of our shipments that did drive warheads on occasion. He had a submachine gun in his cab when he arrived. The security guards found it and all h@ll broke lose. Anyone found on a Nuclear Power Plant site with a firearm is normally going to jail. This driver had a Special Federal carry permit. So, security safely secured his fire arm and he got it back when he left. Why the driver didn't declare it when he arrived I have no idea.
I must be wrong about the placard then.
I am going by memory from 35 years ago of what dad told me.
He never hauled nuclear waste. He hauled other hazardous chemicals.
Every once in awhile though he would haul some household item. Like Palmolive dish detergent. He brought the trailer home before taking it back to the terminal to get cleaned out. We had multiple buckets of dish detergent.
Another time he hauled raw sugar. There was still a little left in the bottom of the tanker in the tubes. We filled up a couple of brand new Rubbermaid trash cans with sugar. Gave it to all our friends.
He mostly stayed east of the Mississippi. Although I remember once hauling a tanker of jet fuel out to White Sands Air Force base in NM. Probably the tanker coming on the railcar was late shipping.
Dad was an owner operator. He was leased to drive for Chemical Leaman out of PA. We lived south of Buffalo.
One of the more frequent and better paying loads was hauling rocket propellant to Anniston, AL. Where they made the ballistic missiles.