Semitrailer Lighting Regulations


Every vehicle that you can drive on a public road has specific equipment regulations. Proper lighting is one of these regulations, as lighting makes your vehicle visible and can help avoid accidents. Lighting requirements vary by vehicle type. For example, if you drive a semitrailer, you should know the United States Department of Transportation (DOT) regulations for semitrailer lighting.


  • Semitrailers must have turn signal lights on the back. There must be at least two red or yellow turn signal lights located 15 to 83 inches off the ground.

    Taillights are necessary on the back of semitrailers. Each semitrailer needs a minimum of two red taillights located 15 to 72 inches from the ground.

    Semitrailers must also have no fewer than two brake lights. Brake lights must also be red and located 15 to 72 inches off the ground.

    At least one white-colored license plate light is also necessary. This light has no specific location requirement. It must only be in a position that allows it to illuminate the plate, so that the number is visible after dark.

    A semitrailer that is 80 inches or more wide also needs at least two red rear clearance lights. These must be on each side of the top rear of the trailer. A set of three red rear identification lights must be present at the center top of the trailer.


  • Semitrailers must have no less than one red rear side marker light on each side. These should be as close to the back of the trailer as possible and 15 to 60 inches from the ground. There is no maximum height for these lights on a trailer fewer than 80 inches wide.

    Semitrailers also require a minimum of one yellow front side marker light on each side. These lights go as close to the front of the trailer as possible and a minimum of 15 inches off the ground.

    Trailers that are 30 feet or more in length also need at least one yellow intermediate side marker light on each side. These should be as close to the center of the trailer's length as possible and at least 15 inches from the ground.


  • Semitrailers that are 80 inches or more in width must have at least two yellow front clearance lights. These lights should be on the trailer's widest points and as far from the ground as possible. Semi tankers may have these lights below the tank.

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