Well, herds of deer tend not to wear wristwatches, os they may not have known it was rush hour. Herds are herds – and deer are not particularly smart animals. They have a leader, and the others just follow. My guess is that the leader of the herd thought that there was food (or water, or shelter) on the other side of the highway and he was going to lead his crowd there. And the followers blindly followed. Deer don’t have high level analytical and thinking skills. (what’s a car? Maybe this isn’t such a great idea!). They go by instinct for food and water. Remember that in a deer’s world, a large object is a tree or rock – neither of them move. Cars don’t fit their world view.