text: To make the cars smarter, they need to have newer systems put into the car. The text states, "they needed a whole lot of senors." Google modified a Toyota Prius with position-estimating senors on the rear wheel. They also put a senor on the roof. Google had placed cameras and the rearview mirror. They placed four automotive radar sensors in the car along with a GPS reciever, and an inertial motion senor.