You can modify tracks so that sessions occur at night. However, the headlights in the race series cast no light whatsoever so you cannot see where you are going.
you do not have to modify tracks. open your profile save file (.plr) and find section "race time" or something similar. then just change time to 2:00 for example. do it if you like to be a batman as Ross wrote there is no light from the headlights in this series. its very strange cos game engine supports nigh racing - see GTL or GTR2