Why do Japanese people turn away and look elsewhere when you (foreigner) sit next to them on a train or bus?

Question:

Rudeness?
Racism?
or
Politeness?
Way they do things in Japan for all not just foreigners?

Answer:

I actually asked this question to some of my friends a few years ago and the general consensus was:

1) Japanese actually avoid sitting next to each other if at all possible just because of personal space issues. Though they would rather sit next to each other than next to us because:

2) They are scared we will try to speak English to them.

The latter seems to be pretty accurate. I have noticed a lot of Japanese will avoid you, even like shop staff girls, until you speak Japanese to them. I think it is probably prompted by an overall uncertainty about foreigners.