The 1904 Sturtevant "horseless carriage gearbox" is often considered to be the first automatic transmission for motor vehicles. Developed in Boston in the United States, this transmission had two forward gear ratios and engine-driven flyweights which controlled the gear selection. At higher engine speeds, high gear was engaged. As the vehicle slowed down and engine RPM decreased, the gearbox would shift back to low. However, the transmission was prone to sudden failure, due to the transmission being unable to withstand forces from the abrupt gear changes.