The stress of commuting isn't from the physical act of driving, but from having to negotiate a crowded space. Regardless if it's a highway, bus, or a sidewalk, when you're in a crowd, you're forced to play a zero-sum game with the people around you.

I disagree. The stress from driving doesn't come just from navigating a crowded space. It comes from the potential consequences of making mistakes. If I bump into someone walking on foot, it's no problem. Once I'm on a bus/train/etc. you have your own space. Granted, it might not be a lot of space, and sometimes it might be uncomfortable, but it's hardly stressful.

Bumping into another car when driving is a completely different beast. Now I need to deal with insurance companies, and it might cost me a lot of money. Or I hit something inanimate and I'm still doing a lot of damage to my car. That's where the stress comes from.