The handbrake is usefull to stop your car rolling off, but on tight corners it is also most usefull. If you need to negotiate a hairpin corner then if you can get the car turning, then depress the clutch and pull the handbrake this will lock the rear wheels causing them to skid around. If you time all of this properly it is much faster than turning the steering wheel. One disadvantage of a standard handbrake is that when you pull it on it stays unless you push the release button. To avoid this rally cars reverse the button, so that you push the button to make it stay on, a so called fly-off handbrake. If your not used to one then most people get very confused and cannot get the handbrake off. Of course to take the handbrake off simply let go. The other disadvantage of standard handbrakes is the amount of force required to lock the wheels. To alleviate this rally cars generally use a hydraulic handbrake, either connected in parallel with the standard cables or on a seperate lever. These have the rear brake line coming in, and then go out to the rear brakes. The cylinder is chosen to get maximum pressure for minimum effort.