Belgium block?

show the property lines. Why can't you straighten it even with the edge of the garage?

You could put curbs or fixed guides but most likely, people will still run over them and possibly damage their vehicles. Even with car cameras, our neighbor's guests and teenager have taken out a couple of small trees while backing up on their curved driveway.

It's established the grass won't grow, you could add a layer of river rock at the curve and further away, add a vertical element like a tree on a mound to signal the change.

Landscape lighting along both sides would help at night. During the day I'd tell people to back into the wider curved space at the top and turn around and drive out instead of backing up.

Widen the driveway only where the cars run off. You can buy some big orange cones (or much cheaper short "soccer cones"), set them out, and see where they get knocked over. Or just look for worn grass and tracks in the dirt.

I have a 6000 sq ft horseshoe driveway and delivery drivers cannot even manage that 😒 They seem to not care since it isn't their yard

I like eld's suggestion. You could also consider lining the driveway with some sturdy, taller hedge/bushes that would provide a visual reminder to drivers. It would also spruce up your yard, and you might like the way that looks.

Add some landscaping that includes boulders. Cars don't go over boulders.