I don't think that would matter. Googles driverless cars use 3D laser scanners which don't require any ambient light. Plus, computers can theoretically see a lot more of the spectrum and therefore see a lot more than we mere mortals. They could look at the road ahead an know exactly what temperature it is, and possibly even see black ice. They could see a ninja on a black horse, at night, in the rain and fog, from miles away using thermal imaging.

Daylight driving, to a machine, would probably be more difficult than night time driving simply because there's more stuff happening on the roads during the day.