I love my car and I'm not ashamed of it. It's true, I don't want to be on a train or in a bus with you (or any other stranger) but I don't think fear is the right word for that. Sometimes there are people on mass transit who do seem like they might be dangerous, but usually everyone is clearly harmless and it's still unpleasant for me to be around them.

I used to think this dislike of being physically close to other people was a human universal but apparently it isn't. The best analogy I can come up with for someone who doesn't share it is that people are like an annoying noise. The more people there are and the closer they are to me, the louder that noise is. Being in a crowded train or bus is like standing near an ambulance with its siren on. It's not scary, and it's not unbearable. I could stand next to that ambulance if I needed to, and sometimes I do. It upsets me, I can deal with being upset, but I'm willing to spend a lot of money (and to pollute the environment) in order to avoid it.

(Even if I always had the entire train or bus to myself, I would still prefer to drive because taking mass transit is usually much slower than driving. But that's a separate issue...)