I suspect it's more clearly visible since I have anti-aliasing turned off, but it's quite annoying in dark tunnels and at high speeds. Wouldn't be so bad if the pixels were black, rather than white. While driving I really have white pixels dancing all across the screen. View screenshot in original size please.
Those pixels are caused by tiny gaps between the tubular segments those tunnels are built from. As you go by at high speed, they look like you described. Here's a screenshot of one of those gaps.