An aspect of Google’s project often lost on the casual observer is that its cars are not completely autonomous, even when no human is helping drive them. In order for the vehicles to function the route needs to be driven by a human ahead of time in one of the test cars and mapped using its array of sensors. This rich set of mapping data is then stored on a Google data center and a portion of it is loaded into the car’s hard drive. The location of stoplights, school zones and anything else that is reasonably static is marked so the car will acknowledge them without having to interpret them in real-time.