<p>This invention relates to an air brake system on a towing vehicle that, in extension, has an override capability in relation to a hydraulic brake system on a towed vehicle, where the towed vehicle is driverless. The extension components are removably mounted in the towed vehicle with connection of its brake pot with the brake pedal of the towed vehicle. Normal braking and emergency braking are effected through this connection but are initiated differently.</p>
