• While LED lights are used by many carriers due to reliability, no official rules have been issued on when an LED light with failed diodes must be replaced.
• Some officers will write a citation on an LED light if there is a “dark area” on the lens due to diode(s) not functioning.
• Many states require officers to look at the light and, if it is still clearly visible from 500 feet away, then no citation is written.

Many carriers have decided to go with light emitting diode (LED) lights for several reasons, the main one being reliability. However, an ongoing issue with LED lights is defective diodes within the bulb. The problem arises due to the fact that there have been no official interpretations published by the Federal Motor Carrier Safety Act (FMCSA) or the National Highway Traffic Safety Act (NHTSA) on when an LED light with failed diodes must be replaced. Therefore, officers decide, based on various factors, whether to write a citation for an LED light with diodes out.

The manufacturers state that if enough diodes are out that the candlepower requirements cannot be met across the entire face of the bulb, it must be replaced (the candlepower requirements are in 571.108). Using this information, officers take one of two approaches:

• Some officers will write up the light if there is a “dark area” on the lens due to diode(s) not functioning. In some models, this means that one diode being out (in a five or six diode bulb) could result in the light being written up.
• Other officers will look at the light and judge whether it is still clearly visible as the type of light it is supposed to be from 500 feet away. While not directly used in the federal regulations, the 500-foot standard is how many states’ traffic codes determine if the candlepower requirements are being met.

Canadian standard: Canada, on the other hand, does have a requirement. Canada’s national safety standards state that once 25 percent of the diodes are not functioning, the light is to be “rejected” as a working light.