Your eyes need to adapt to these changing conditions, which is all part of endurance racing at night. It is much harder to judge the braking points and your field of vision narrows so much faster around you at night.
As a driver, you must be able to take a cat nap with all this commotion around (there is typically only 1 trailer per 4 drivers!), then be ready to drive at your best shortly after you wake up.
These great shots from last night's testing at Daytona really help get the event's atmosphere across!