According to Arthur de Wolf's blog, two autonomous Connexxion shuttle busses collided in Rotterdam last week. The robot busses hit each other on a narrow bridge where they were supposed to wait for each other to pass. Fortunately there were no passengers at the time. The Busses are known as Frog People Movers (i.e, People Movers made by a company named Frog, not vehicles to move Frog People). Frog is one of the companies working on the CyberCars initiative to develop autonomous vehicles for use throughout the Europe. More details on how the shuttle bus system works can be found in a 2002 summary of the system that includes photos of an older prototype of the busses.