Any light that you put on a commercial vehicle must work even if it is not a requirement if it is there it must be functional or it is subject to an equipment failure ticket. That is how it is here in Washington State anyway. I once got an equipment failure ticket for a clearance light on the outside of the mud flap on a log trailer, this was on a truck equipped with a self loader so the trailer was a hop on, witch means it could be stacked on the back of the truck like other log trucks but without disconnecting it from it tow point first as the reach will fold and the electrical cord stays attached. Anyway my argument was that the trailer was on the truck, not on the highway and if it were a standard long logger with the trailer up the trailer would be unplugged and none of the lights on the trailer would be on. Well I still had to pay the ticket and I was told all lights must work. BTW I still feel I was right but the state still got their money!!!
