Change Road Hazard
Under road hazard / side of road. Remove missing sign. Add Tractor/Trailer. If I am new to a area I really wouldn't know what sign is missing and if I am from the area I probably wouldn't notice it missing. We see more cars on the side of the road but the big rigs are bigger and more likely to be hanging out in traffic,
Actually, it should probably be changed to 'traffic light out or malfunctioning'!
I usually USE it for that purpose.