why do some 18 wheelers have green lights on the side?

Question

i was driving from arkansas to texas and noticed that about 1 out of every 4 eighteen wheelers had a green light on the side behind the drivers side door and i was wonderin what this is for.

Answer 1

I am a mechanic for Werner Transportation. The light you are refering to is called a utility light and like the first answer it is for working behind the cab usually hooking/unhooking the lines from the tractor to the trailer. It comes from the factory as white and by DOT standard we are required to replace them with white ones whenever we see them a different color. It is against most state laws to ride on the road with a white light on facing toward the rear of the vehicle. They replace it with a different color so they can leave it on while on the road. Truckers seem to think the more light the better for some reason

Answer 2

I drive/own an 18 wheeler. I don't think I have ever seen many of the green lights that you mentioned. But the light is known as a Cab Light, and from the factory is a White light (used for working
behind cab of truck or front of trailer) but often times gets replaced by different color lenses. Red or Blue are the most popular colors. Then once they replace the lens they leave it on full time. I guess it has something to do with MORE lights! Not sure.

Answer 3

I agree with the first answer.... There is a work light behind the cab of the tractor that comes with a clear lens from the factory.... Some drivers prefer to replace the lens with a different color. I've seen red, blue, green, purple. There really isn't any point to having this light on while driving, its driver preference. Hope this helps also.

I'm a professional driver also.

Answer 4

I drive an 18-wheeler and the light you're referring to is actually on the trailer. It is a reefer operation indicator light. Green means not problem. If it turns yellow there is then a problem that needs IMMEDIATE attention .