As you know, I'm a fan of the clearance lights. Someone mentioned that they are used to determine if you can fit under a bridge or whatnot, by observing how the lights are illumating the obstacle. So I had to drive down to SF and without thinking of parking garages, we booked a downtown hotel. When we get there the parking garage has a bar at the entrance the says the clearance is 5'-10"
I know my truck is just under 7 feet I think. The manager said I would fit, and if it was close he would move the bar for me so I could fit in (which he had t o). I wasn't sure but proceeded with caution. As we were going under I beams that were painted white I was observing the light that my clearance lights were giving off, and I can say it actually does work. It's funny because I had just read the latest comments about this recently on here. It's not perfect, but I used it, and it worked.