Towed vehicles can be extremely heavy. Accordingly, it is too much of a burden to the braking system of a towing vehicle to not have brakes on the towed vehicle. Controlling the brakes of the towed vehicle must be accurately applied otherwise undesirable conditions can be created. There is a need for a method for controlling braking of a towed vehicle. This method comprises receiving a first signal via a communication bus of a towing vehicle, the first signal relating to at least one operating condition of at least one the towing vehicle and a towed vehicle, sending a second signal to brakes of the towed vehicle, the second signal based on said first signal.