Comment by JoeAltmaier

Nobody suggests driverless cars are working open-loop from GPS coordinates; no current driverless cars work that way. Its generally a combination of gps, local sensors including sonar, radar and cameras, and car-to-car networks. The UofIowa Driving Simulator has done studies of trains of cars linked by short-range networks, where they coordinate braking and acceleration to achieve inter-car distances of a few feet.