Safety feature for a vehicle trailer

A trailer 130 is provided for being towed by a tractor unit 120 which provides command signals to trailer 130 through one or more couplings 200 on the trailer to operate trailer safety functions. Trailer 130 has a control unit configured to operate safety functions of the trailer independent of couplings 200 and to operate safety feature lights which are present in parallel to safety feature lights operable by signals from the tractor unit via couplings 200. The safety feature lights are provided power in parallel to existing lighting units. The safety features can be both brake lights and indicator lights. A diode arrangement, for example two forward-biased diodes in parallel, may be provided to prevent power applied from the control unit being fed to tractor unit 120.