What is the purpose of lights on the roof of big trucks? (vehicle, 2012)

[PokerMunkee]

I'm not sure what they are called (clearance lights?), but most 3/4 and 1 ton trucks have them on the top of the cab. What's the purpose of the lights?

[Coldjensens]

They help the drive see better when it is dark.

[PokerMunkee]

Originally Posted by Coldjensens

They help the drive see better when it is dark.

[mathjak107]

they look cool!

seriously though ,for off road use the higher up you get the lights the further out they can throw. many states force you to have covers over the lenses when not off road.

[Momotaro]

Common use in my hometown is to illegally hunt at night. They use the lights to make the deer panic and not move. It is an easy kill.


edit: I did not see the picture the op was referring to. The lights I am referring to are spot lights I see in my hometown.

[bmrisko]

Marker lights required by DOT for vehicles/trailers over a certain width...

[Grandpa Pipes]

These roof mounted lights are "clearance" lights since the trucks they are used on a work trucks that sit higher than a normal 1/2 ton truck.

Why clearance lights?

To mark the top most outline of the truck per DOT for a wide variety of overhead clearance needs.

[reed303]

I believe the OP is asking about "clearance" lights, not roof-top off-road lights. They seem to be required in the US on vehicles over 80" wide. This probably started in the 1920's or 30s when the headlights on trucks were much closer together. See Automotive lighting - Wikipedia, the free encyclopedia

A 2012 GMC Sierra 1500 is listed as 80" wide.

[PokerMunkee]

Thanks, clearance lights is the name. Found a 100 post thread on a Ford forum going over it. This is the best explanation I found:

The way it was explained to me at CDL school, is the clearance lights are there so other drivers will know when a larger vehicle is on the road. When traveling down a two lane highway (1 lane each direction), then it helps to know when an on coming vehicle is taking up the majority of it's lane. Most of us will inch over to the right when approaching a big rig but may not do the same when the vehicle appears to be smaller (such as Civic or Prius etc). Headlights alone do not communicate how wide the approaching vehicle may be so the clearance lights help. It becomes more critical when you are hauling a wide load yourself because you may not have much room to move over so both drivers need to know they each are approaching a wider than normal vehicle.

Amber lights means the vehicle is heading towards you. Red lights means that the vehicle is heading the same direction as you are. This is super important because a vehicle can be in your lane and if you see amber lights then you know it may be trying to pass another vehicle and a potential danger is present. If red lights are ahead, then you automatically know that a wider vehicle is ahead and it may be traveling slower than you so beware.

So, it's all about safety as far as I can tell.

So, why have cab lights on SRW trucks if they aren't over 80" wide? the answer is that sometimes a SRW truck needs clearance lights if it's been fitted with a specialty bed (such as glass racks) or if the truck is towing a trailer that is wider than 80". Most all box trailer or RVs have the necessary lights so the tow vehicle doesn't need them but what about flat bed or boat trailers? My boat was 102" wide so the tow vehicle needs clearance lights to be legal. My SRW truck came with cab lights from the factory but my wife's truck did not. I was actually pulled over when I was using my wife's truck to tow the boat and the officer let me off the hook with a warning. I added cab lights a couple of weeks later. The officer wasn't being picky, he was 100% correct. The road to the lake is a dirt road through some canyon passes and it's only a single lane in some places. So on coming traffic needs to know when a wide vehicle is approaching.

[frankgn87]

on pickup's its only used for a styling feature. I have a huge 2500HD Chevy for work and I ordered it with the lights. My bud has the exact same truck as mine in a GMC and his was not ordered with them.