Yes.
All required lamps must be operational on the rearmost vehicle in any combination (e.g., brake lights, taillights, turn signals, four-way flashers, clearance, identification, side marker, license plate lights). (49 CFR §393.9(a) and 393.11)
All required lamps must be operational on the rearmost vehicle in any combination (e.g., brake lights, taillights, turn signals, four-way flashers, clearance, identification, side marker, license plate lights). (49 CFR §393.9(a) and 393.11)