I like the idea of something like banger bars/chains hanging over the roadway. I suggested a chicane to my local road works but there’s no room for the here. You could probably do it easily for the notch though. A chicane on each side to get them stuck in a place that they can be removed from easily as opposed to all the way up the road.

Edit: I was thinking about the chains/bars for my own local issue, not for the notch. I still think a really tight, extreme chicane on both sides could work nicely to prevent this. It wouldn’t take up much space and wouldn’t do anything to normal traffic flow other than cause a brief slow down, which is how I’ve seen them used elsewhere - as traffic calming devices.