When I walk (or run) I am generally in a hurry, because I am more likely than not to be late!
Like others, what I hate the most is when I am stuck behind groups of people spread right across the pavement so there is no room to pass them, and they seem totally oblivious to the fact that they are in the way.
I also hate it when people just stop suddenly in front of me (usually in order to use their mobile phone!)
I have been known to actually say "Hey - you ought to be fitted with brake-lights!" at them, if they do it really suddenly.
But I also hate being in a stream of people coming fast at me in the opposite direction - I find it overloads me and I get really on edge.
One other thing I do (and I only ever knew one other person, a guy I used to work with, but not an aspie, who did this) is suddenly to realise I am running, without having consciously decided to do it.
It is a very childlike thing, like how children spontaneously run & skip. Other people must find it really odd when I do this. At home I spontaneously dance too, and it is really hard to remember not to do it at work. (If I have to, I go to the toilets, but people always come in & interrupt me.)