If I had contact or Lasik, I would be able to see in a split second glance...however glasses screw that up nicely.
However I have been known to look for about 2 seconds, then scan teh front, then another 2 seconds, rinse wash repeat...for a while.
I also turn my head to the side to cut back the wind turbulence around my ears so i can hear behind me from time to time...if I thought I heard something, I do this to make sure.