All commercial vehicle violations need to be corrected, but not all violations are as bad as others. This is why the Commercial Vehicle Safety Alliance (CVSA) has a standardised list of violations which are so severe that they result in an out-of-service notice (meaning the vehicle cannot be driven until the repair is made).
There are times when a violation can become an out-of-service defect quickly: when you hook or unhook from a trailer. If your tractor’s brake lights do not work but you are pulling a trailer with working brake lights, your combination is not out of service. Your missing tractor brake lights are still a violation, but since the trailer’s brake lights are working you would not be placed out-of-service.
As soon as you drop your trailer, though, the tractor is now out-of-service.
