There are a lot of reasons why starting a roadtrip in the late evening or at night.
Most of the times it is, because you may not have to much traffic. I like driving at night, when you´re on a long roadtrip. Your driving down the freeway and enjoy, that you have cruise control. That is relaxed and fuel efficient. So you´re making the best from sitting hours in the car.
But sometimes there is still a traffic jam. And if you´re a lucky guy, you will have a car in front of you, that is nice to watch at 🙂