We just moved and so far, our actual neighbors are great. But...general people? Not so much

We have a whole parking lot as our driveway. It is our property. Inside our property line. This was apparently a general store in the 50s when it was built. We love the house. Enjoy all the parking even though we only have 2 vehicles.

The other day I stepped outside and someone is parked here. This is private property. I will be putting a note on thier car next time. This is the second time they have parked here. Im not sure how to word it, but I was thinking, 'this is private property do not park here again or your vehicle will be towed' any suggestions or is that okay?

Then today a construction truck stopped and at first I thought he was waiting for the road to clear so he could back up but then he turned it off and got out and got on his phone. And was walking away!!!!! I said excuse me, this is private property you cant park here. He said oh well we are replacing your water main.

First of all, he doesn't work for my city, they all drive "city of..." vehicles that are all white. Second his truck had the name of some construction company from Rolla. Second, while I believe they were working in the street that still doesn't give him the right to just park here. He did leave without much fuss.

Is there some kind of sign that we can get besides the no trespassing signs we already have? Like no parking signs saying they'll be towed at thier expense for parking here? Are those allowed on personal driveways? This is the first home we have owned.