Vehicle with a pneumatic control line for operating the brakes of a trailer.

A vehicle is disclosed having a braking circuit operated by at least one brake pedal (16,18), a parking brake and a pneumatic control line (50) for connection to a trailer to operate the brakes of the trailer when the vehicle is braked. The vehicle comprises a first, pressure operated, valve (60) for regulating the pressure in the pneumatic control line (50) upon application of the vehicle brake pedal (16,18) and a second, electrically operated, valve (82) acting in parallel with the first valve (60) to apply a pneumatic pressure to the control line (50) in response to operation of the vehicle parking brake.