Deer are just not wired to understand that a man-made object moving at speed is a threat to them. If they want to cross the road - well, they're darn well going to do it. Whether it's the male leading them across the road or the does and bambis that follow, trusting their leader. :yesnod:
I just had the opposite happen to me in the car the other morning.
As I came around a sweeping turn to find two deer on the shoulder, the first deer crossed, the second deer started to cross, turned its head in my direction (apparently saw my car approach) and then turned around back into the woods.
I'm assuming the second animal saw my car approach, perceived it as a threat and took evasive action. Next time, in the interest of science, I'll track it down for a debriefing.
(Of course, the local deer population benefit from our superior North Carolina educational system and general distrust of Cervidae community authorty figures.)