What is RSP or RSS?
Roll Stability Programme (RSP) or Roll Stability System (RSS) is an R13 mandatory feature built into new electronic braking systems. The specific mechanics and logic depend on the manufacturer but it typically uses a number of sensors, including (but not limited to) lateral acceleration, vehicle speed and axle/bogie load.
The system intervenes when a lateral acceleration threshold has been exceeded which happens when a vehicle travels round a bend too quickly and is at risk of rolling over.
Typically, if the system detects a risk of rollover, it sends a test pulse (low brake pressure) to the wheels on the inside of the curve to determine their state. If the wheel speed reduces, it is likely to be either in the air or very lightly loaded so the system applies high braking pressure to the wheels on the outside of the curve to reduce vehicle speed as quickly as possible.
If the change in lateral acceleration happens quickly, irrespective of wheel state, the system will apply high braking pressure to immediately reduce vehicle speed. This may happen if the driver has carried out an evasive manoeuvre and there would be insufficient time to complete a test pulse. In addition, evasive manoeuvres can swing from right to left so immediate intervention is more desirable.
Oscillation Control (Knorr-Bremse)
In addition to progressive lateral acceleration triggers, RSS/RSP system can also detect swing which it determines by sensing lateral acceleration to the left and right.
If the system detects an excessive number of oscillations, the system will apply individual left or right braking to counter the trailer yaw. Typically, trailer swing is stabilised within 2 or 3 brake actuations without a significant reduction in speed.
Oscillation control is not needed for semi-trailers and not recommended for full trailer applications.
Published: Fri 17 Nov 2023
Updated: Tue 09 Jan 2024