Is it normal to pretend you don't see people around you that you know?

I have really bad eye vision so by the time I know who it is, which is when there like 2 feet away from me, its too late to duck them. :\

I mostly do this because I just don't want to stop whatever Im doing to talk. If I cant avoid them seeing me, I just give a big smile and a "HI!" and keep walking.

I do it all the time. Ducking behind cars usually works best when walking down the street. Run the other direction in any store. Try putting in headphones, so people are less likely to walk up to you. XD

It's called social anxiety I think?

I sometimes do it but not because I don't know how to talk but because I just dislike them..
I think it's a matter of self confidence..