d) Continuous Service Brake System
The provisions of the EC stipulate the use of continuous service brakes for vehicles of the classes M2, M3, and N3, if the service brake does not pass the prescribed tests (type I and II). The function of the continuous service brake system has to be guaranteed independent of the condition and efficiency of the remaining brake systems.
The German Straßenverkehrszulassungsordnung (Road Traffic Registration Authority) goes beyond this. It stipulates continuous service brakes for all commercial vehicles and trailers with a permissible total load Gmax perm >9 t and all busses with Gmax perm >5.5t.
Here, the continuous service brake when independently operated should ensure an uninterrupted speed of v = 30 km/h (19 mph) over a distance of 6 km (3.7 miles) on a 7% downward gradient.
The ECE-R 13/05 represents the existing law within the European Community. In other countries often different provisions have to be observed, such as the existing Federal Motor Vehicle Safety Standards (FMVSS) in the USA.