Even between cities. For a while I was driving between Portland and Seattle pretty often, and the traffic was always awful! I would love to be able to take a HS train.
I certainly think it's better to be stuck in a traffic jam and sit in your own car than stuck in a traffic jam inside a packed vehicle full of other (sometimes extremely unpleasant) people.
Not when it means you're stuck in a traffic jam. In a big city I'd take decent metro system over a car any day.