Road to the driverless car

All that data being pumped out by all those sensors gets channeled to computers that calculate what the car should be doing at all times, given what the driver is doing with the steering wheel, gas and brake pedals. (In most modern cars, this data is also fed to a recorder that "remembers" several seconds worth of data and holds on to what it remembers in the event of a collision. That stored data can be used by accident investigators.)

If the computer senses that the car is doing something that doesn't match - say one or two wheels are spinning too fast or the car isn't following the curve it should - the computer sends commands to actuators (basically tiny motors) that handle brakes, the throttle and possibly even steering mechanisms.

For now, all these computers do is make sure the car is doing what the driver is telling it to do. Ultimately, preventing a crash is still the driver's responsibility.