How do i turn on a motion blur effect in GTA 4 for pc?

I saw my friends gta,which is on xbox 360,and it has that motion blur effect,post processing.SO why this isnt enabled on PC?How do i turn on a motion blur effect in GTA 4 for pc?Press P in game. It'll also smoothen the edges, however may give you a overall blurish look to your game. I personally do not use it and am ok with no motion blur.