• Lighting standards exist to make the behemoths safer for everyone.Cement trucks 3 image by beverly from Fotolia.com
  
  Tractor trailers aren't dangerous; not knowing where they are or what they're doing is dangerous. The federal government recognized the special needs of large vehicles long ago when it instituted the many lighting regulations in place today. By and large, these regulations exist to both define the outer edges of the truck and to ensure that other drivers have adequate information as to its orientation, position and the driver's intent.
  
  

General Laws

• All required lights on a truck must be present and functioning at all times. Hazards and turn signals need to flash when appropriately triggered, and brake lights need to activate whenever the pedal is depressed. It is the driver's responsibility to ensure that the lights function properly before, during and after a trip. In states where under-body neon lights are legal for cars they're generally not for trucks. The tractor-trailer's tall ride height means that the neon tubes will usually be visible from some angle, which is illegal almost everywhere. You can have still have underbody lights on the truck, you just can't use them on the street.
  
  

Headlights

• Headlights must be maintained in good working order and be of the original type installed in the vehicle. The federal government doesn't set any specific standards as to how you adjust the lights. A good rule of thumb is to park the truck 25 feet from a wall and adjust the low beams so that the bottom of the beam just touches the base of the wall.
  
  

Tail Lights

• Tail lights may be either a colored bulb inside of a red housing or be of an LED design that uses dozens of individual red lights in a common housing. You must have at least two tail-lights on the back of a tractor's rear bumper, and nine on the back of the trailer. You need to have three tail-lights on the top-center, two each on the outer bottom corners, one each on the outer top corners. You need to have at least two more on the bottom rear corner of the side of the trailer.
  
  

Trailer Marker Lights

• Amber marker lights exist to define the outline of your truck so that other drivers know how big it is. At the very least you need four marker lights per side (one each on the top and bottom front-corners and one in the top and bottom center) and two on the front in the top two corners for a total of 10. You can, however, put as many additional marker lights (a.k.a. "chicken lights") as you please around the perimeter edges of the trailer.
  
  

Tractor Marker Lights

• On the front of the tractor you must have five amber lights above the windshield; two on the truck's our edges and three in the center. You must also have two in the lower-outer extremities of the front bumper, and two amber marker lights on the side of the truck near the lower-rear of the cab. Some states mandate that trucks must also use an amber reflector mounted on the lower-center of the side of the cab, so most trucks have them just to stay legal in all 50 states.