I have the same problem. I've thought about building a little cat shelter near the carport. The cats are going to go where they want to, so might as well make them want to go somewhere that isn't my car.

You need those pointy nail type looking things that cities put on signs and ledges to keep pigeons off. Just glue a couple of hundred of those on the hood of the cars, and problems solved.

Call animal control every time it is loose. The city will get pissed off and come down on the owner.

Once a lady we worked with (housekeeping) got her first new car, single mom raised her kids out the door and her first real treat for herself, she came into work one day raising hell because cats were getting on her new car and the sand on their paws were scratching it all over.

The next day she came in and said she put a bowl of antifreeze outside......I was scared to ask her how that worked out!

I would contact the neighbors and request they restrain their cat. Then I would call Animal Control if neighbors refused to comply.

Then I would deal with nightly keying of my car by the neighbors in retaliation for their cat getting picked up, haha.

Scary!

I've started trapping the cats that roam around my house. I spent $45 dollars on a trap at the local feed store and a couple of bucks on sardines. Very much like the one in this picture, but smaller. So far, I've taken three cats to the local shelter. They say they spay/neuter and then relocate the cats. I'm hoping the relocation point is far away from my house.

Yeah that's much kinder than maiming crippling or killing them, or as the old folks where I grew up would say "Taking them for a ride", dropping them off far far away.