I have several 90 degree wide bends in the road between town and my house (this is not my cycling route, 99% of the time). The road has about a 2 foot shoulder. Almost every car cuts the corner so tight that they're OVER the shoulder and on the gravel. People on the outside lane are sometimes 2+ feet into the inner lane.

When I'm in my car I make it a point to stay inside the lines. If there's a car coming the other way, I try to hold my line and make them get the hell back into their lane. Sometimes I wind up giving a little to avoid a collision, but they get an earful of horn for my trouble.

I think I've seen a SMALL amount of change in the number of people that stay in their lanes around those corners since I've started doing that.

I DO ride that way sometimes, and I'd prefer it if people weren't coming up behind me (usually 20+ over the posted limit) driving straddling the shoulder...