Sorry if this isn't I the right thread or whatever guys. But I've always been curious. What is the purpous of can lights. And why is there always 5. Dodge, Chevy, and ford. And all the big rigs. Jw any and all replies would help!! Thanks y'all.

 

they are cab marker lights they are there for marking the top of the cab not only do they do that but they look good

 

Five on the top rear of tall trailers, Five on the bottom of wide trailers and five on the front top of tall cabs. A.K.A. clearance lights

 

Lol. Yeah. I got all that. But why 5. And like what are the orgins. How did they start??

 

The three in the middle (on the backs of trucks) Are a specific distance apart. This is supposed to aid a motorists following the truck to judge the distance. The two outer ones to mark the corners.

 

After a certain width the Federal commerce comission (FCC) requires them. Regular pickups dont require them duallys do.You even see the 3 lites together centered on boat trailers that are over the width.

 

I've heard the three in the middle called I.D. lights, to identify vehicles that fall under commercial vehicle ordinances, one ton and up trucks, large trailers, etc. The outer ones are clearance lights to mark the edges of the vehicle. Then on a dually there'll be lights on the fender extensions to mark the widest part of the vehicle.

 

Thanks guys. Appreciate it. Realize it's probably a stupid question . But I've always been curious!!

 

cab lights used to be only turned on to identify a loaded truck there for getting the right of way on older narower highways.