A visual indicator assembly and adaptor for a trailer includes an control circuit, an input lamp plug electrically coupled to the control circuit, an output lamp plug electrically coupled to the control circuit, and an identification lamp plug electrically coupled to the control circuit. The input lamp plug is connectable to a trailer lamp plug of a lamp wiring harness of the trailer. The output lamp plug is connectable to a stop lamp of the trailer. The identification lamp plug is connectable to a corresponding identification lamp plug of the lamp wiring harness. The control circuit is configured to supply a first voltage signal to a plurality of lamps of the trailer in response to a power signal and supply a second voltage signal to the plurality of lamps in response to a brake signal. The second voltage signal is greater than the first voltage signal.