Division 2.1.1.4 F1
United Kingdom
It is not permitted to fit any adjustable valves that would allow the performance of the braking system to be changed by the user of the vehicle such that, in service, it is not subject to the requirements of this Regulation. An adjustable valve that can only be operated by the manufacturer through the use of special tools or the provision of a tamper proof seal shall be permitted provided that the user of the vehicle is not able to adjust this valve or that any user adjustment is readily identifiable by enforcement authorities.