The benefits of side marker lights are to help a driver to see a truck that is approaching at an angle at night, and to see the truck in time to enable the driver to avoid a collision with the truck. If a collision cannot be avoided at least the damage caused by the collision will be minimized. Increased safety through the reduction of nighttime angle collisions is well documented. Side lamps have been proven effective in preventing nonfatal accidents and serious injuries. 

While the Federal Motor Carrier Safety Administration (FMCSA) currently oversees the implementation of federal regulations requiring side marker lights, the National Highway Traffic Safety Administration (NHTSA) originally established the regulations that required the installation of these lights on trucks. The NHTSA followed up with an extensive study over the period of one year about the effectiveness of side marker lights on trucks. The following important conclusions were reported by this study:

> The frequency of angle collisions occurring during the nighttime was significantly reduced.

> The number of nonfatal injuries occurring during nighttime angle collisions was reduced. 

> The decrease in the severity of nonfatal injuries was attributed to the reduction in the severity of the accidents because the side marker lights were visible.

> Sighting and stopping distances were increased for the approaching driver.

> During the study period which involved the states of North Carolina and Texas, the study report said that 106,000 accidents and 93,000 nonfatal injuries were prevented. Over $340 million in property damage was also prevented. These numbers were based on the NHTSA's statistical analyzes of the data from the two states.

Side marker lights are cost-effective. A truck without these lights that is involved in an accident can become the target of a lawsuit. If this accident happens in a state that allows contributory negligence as grounds for a lawsuit, then the truck driver and the truck owner could find themselves as the target of legal action.

Another problem arises when a truck that is involved in an accident does not have the mandated side marker lamps, because the driver and the owner can be accused of being non-compliant with the federal and state regulations even if the cause of the accident was something other than the lack of these lights. Being in violation of any mandated requirement lends credibility to being negligent in other aspects of truck maintenance and equipment. All of this can be avoided for a nominal cost.