Many accidents involve a loss of control on the part of the driver. This can be due to misjudgement - going too quickly into a corner for example - or because the driver is forced to make a sudden manoeuvre to avoid a hazard,
The driver may not be aware that the Stability Control system has intervened.
How does it work?
Stability Control systems evolved from other technologies such as ABS brakes and traction control. For those to work, braking systems had to be developed which could sense when a road-wheel was about to lock up and could adjust the braking individually at that wheel. This technology, along with additional sensors and a computerised control unit, is utilised by Stability Control.
What should I ask for when buying a car?
The first Stability Control systems started to appear around ten years ago and, by now, almost every manufacturer has a system available. Some manufacturers fit Stability Control as standard on all models; others make the system available only as an option and only on certain models. You should check with your dealer that the car you are buying is fitted with Stability Control.
Check Link
http://www.euroncap.com/content/safety_ratings/recommendation.php