Parking brakes

Every motor vehicle shall be equipped with a braking system (which may be one of the braking systems hereinafter prescribed) so designed and constructed that it can at all times be set so effectually as to prevent two at least, or in the case of a vehicle with only three wheels, one, of the wheels from revolving when the vehicle is not being driven or is left unattended: Provided that this regulation shall not apply to– (a) motor cycles with or without sidecars attached; (b) invalid carriages.