Yep, that's it. The following is from a reviewer's test drive.kemosabe said:...They must have a gyroscope in the vehicle somewhere to detect the change in roll (as in roll/pitch/yaw)...
In order to help reduce the risk of a rollover, the Volvo XC90 is equipped with an active stability-enhancing system known as Roll Stability Control (RSC). The system uses gyroscopic sensors to register the vehicle's roll speed and roll angle.
What does this mean to the driver? Control, safety and security knowing the XC will stay upright.
Volvo had us drive through a coned shaped S course at increasingly faster speeds to simulate a sudden avoidance situation. Volvo called it the "moose" test in honor of Sweden's real world moose population. The idea was to avoid the obstacle and experience the XC90's rollover protection circuitry. When the calculated angle is so great that there is an obvious risk of rolling over the DSTC (Dynamic Stability and Traction Control) anti-skid system is activated. DSTC responds by reducing the engine's power and also by braking one or more wheels as necessary until the vehicle under-steers and stability is regained. This helps reduce the risk of a rollover initiated by extreme maneuvers.
The cumulative result is Volvo's RSC system keeps all four wheels connected to the pavement. I was not able to get the XC90 on two wheels.