I pute cones down behind a paint striper for 5 seasons at 7mph. Other than putting cones down all there was to do was watch for trinkets in the ditches. Have a maverick 88 12 gauge couple pocket knives,leathermans, 1 chainsaw, 1 leaf blower, shovels,rakes,tool boxes,trailer tires, hitches, hitch pins, ect. Found a brand new mattress and box spring i had to pack out of road over bank never went back for it, a 1 inch 4x6 road plate that came out of a rollover in a really deep ditch that sat there for a week before i decided dude wasnt coming back for it.
In the winter we replaced road signs. Found lots of shit doing that to. Same small stuff as above lots of small bills and change, lots of drugs and sex toys. I guess When people wreck and cops and tow truck are on the way first think they think is better stash the meth pipe and dildo so i dont look horny and suspicious.
As for stealing signs just cost the tax payers a bunch of money to replace them but keeps people working i guess. Around here state signs are stamped with property of and county signs have a sticker. Its impressive what it cost the county to replace a sign. Seen it twice where supervisor had to go with cops and identity our signs hanging in someone's garage that had pissed the cops off and had a bunch of our signs.
Just to keep rambling ones that where constantly stolen we would pour them in giant concrete balls. Then they'd unbolt sign so we would theft nut the hell out of them. Then they would just cut the post off so we would grease the shit out of them. Usually solved the problem especially at school bus stops where kids like fuckin with them.