Grade separation would work in warm climates, but anywhere it may snow it is somewhat dangerous as hitting the hidden curb could send you out of control. In on

Grade separation would work in warm climates, but anywhere it may snow it is somewhat dangerous as hitting the hidden curb could send you out of control. In one street of my city the parking was replaced with two way bicycle lanes, and there are plastic bollards to separate it from the road (which is probably around 9 feet now as you suggest). Compared to a grade separation that isn’t going to do much if you go over it, if you hit a bollard it’s going to leave a nice permanent mark on your car, so you are going to drive more carefully. The only issue I’ve seen with this is if vehicles need to deliver to the shops and bars on this street, they have to park in the cycle lane (there is no rear access or parking).