text: The development of these cars will also prevent accidents. Google's Toyota Prius, for example, uses a spinning sensor on the roof. The sensor uses laser beams to make a constantly updating 3-D model of everything around the car. This can help the driver be aware of things surrounding their automobile, such as other cars, animals, or pedestrians. With the help of this sensor, drivers will see more things surrounding them, preventing accidents. Google's cars have driven more than half a million miles without a crash.