Eyes don't have uniform resolution. The centers of our eyes (or what we're focusing on) have very, very high resolution, while the outer parts have much lower. Cameras normally have something like a middling resolution in comparison.
[0] http://www.rit.edu/kgcoe/iros15workshop/papers/IROS2015-WASR...
I mean, we could be focusing 100% on the road ahead, and can still respond to peripheral events lightning fast..
I think this is why a lack of sleep can quite adversely affect driving. It seems that if you haven't slept well. the "behind the scene" processing takes a hit, which greatly impacts driving capability..