Originally Posted by bmwforme
a few reasons could be
1. flash to pass
2. they could think your highbeams are on because your lights are naturally bright..
3. admire your car, i sometimes give a thumbsup like this
4. giving you the right of way or saying go
5. your lights are off
6. warn you of a danger ahead, car wreck, animals, stopped traffic, speed traps..
Its number 2 cause its at night where you can't even see my car cause its black lol. But everytime I drive at night im always getting people flashing me I get a kick out of it though.