Here is why trucks have 5 little lights on their roofs


Posted by: Hassana Obi

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Have you wondered why big trucks often have 5 little lights installed on their roof but not 4 or 6? What is the purpose of these lights? Dive in and see Naijauto’s explanations!

1. Types of vehicles that need lights on top

According to the Electronic Code of Federal Regulations (e-CFR) of the US government, any vehicle 80 inches wide and onward must have 3 little lamps mounted at a place “as high as practicable” to inform other travelers of an oncoming wide vehicle. These lights are called Front Identification Lamps.

Depending on the width of the vehicle, different number of lamps are required to fit its actual size. Usually, big trucks with large width are required to install at least 2 more Front Clearance Lamps, adding up to a total number of 5 lamps on their roofs.


Some trucks even add extra lights on rear roof bar

So, how is the actual width of these vehicles calculated?

Extract from Federal Regulations defines it as below:

“nominal design dimension of the widest part of the vehicle, exclusive of signal lamps, marker lamps, outside rearview mirrors, flexible fender extensions, mud flaps, and outside door handles determined with doors and windows closed, and the wheels in the straight-ahead position. Running boards may also be excluded from the determination of overall width if they do not extend beyond the width as determined by the other items excluded by this definition.”

Thanks to this definition, which excludes mirrors and fender flares, such seemingly big boys, such as Rolls-Royce Cullinan, do not need to wear those awkward lamps. 

2. Purposes of “wide-load” lamps on truck roofs

There are 2 main reasons for these identification lamps on big vehicles.

  • First, it informs other cars of the presence of a large vehicle on the road, thus alerting them in time to take cautionary maneuvers. That’s why the lights must be installed as high as possible so that oncoming vehicles from afar can see them. It’s also important that travelers can see these lights in their rearview mirrors in case the truck is traveling behind in the same lane. They should be aware that they are about to be passed by a big vehicle.


With these lamps, people can spot a big truck from far away

  • Second, the lamp chain serves as a measurement in dock-like areas to spotters. When a truck is maneuvering around, observers can estimate whether it can fit through an opening or overhead clearance, thereby providing support accordingly.

>>> Can you guess? Why is the word "Ambulance" written backward on emergency vehicles?

3. An interesting case of Identification lamps

To cement your understanding of these wide-load lamps on big vehicles, we cite here an interesting example – the Ford Raptor.

Though the Raptor has none of its business around dock-like areas, this vehicle must install 3 little lamps for identification given its 86.3-inch width.  However, instead of having those lights mounted on its roof, the truck sets them right above its grille. And the government is totally okay with that, how?

If you refer back to the regulations, the law just states “as high as practicable” but does not specify exact locations. Ford is quick-witted, so they place the lamps at a height they consider most practicable right from the very first generation of Raptor.


Three identification lamps are added in harmony with the overall frontal design

Now, the design has become a unique trademark for the line-up while still conforming to traffic rules.

With all the information mentioned above, Naijauto hopes you have fully understood why trucks have little lights on their roofs. Generally, vehicles of 80 inches width and wider need these lights to indicate their large presence on road. The row of lights placed in front is to highlight how wide the vehicle is, all for the sake of travelers’ safety.

>>> Do come back for more Mind-blowing car facts and safe driving tips!

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Hassana Obi

Hassana Obi

Car prices

Hassana Obi is an automobile writer and editor at She prides herself on hundreds of informative and entertaining articles on Nigerian traffic regulations, car prices and celebrity car collections. When Hassana is not writing, she is a teacher and philanthropist.

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