I come in early just for that reason, so I can leave before darkness falls.

It was only after I read the thread about commuting in the dark that I made the decision only to ride to work when I know I can leave before the sun sets.

In the morning (at 5:30 am) there are very few cars and I am on a bike path for the majority of my commute. But in the evening there are tons of cars, so I decided not to jeopardize my life by riding home in the dark.