Beginning before World War II and accelerating after it, most major railroads installed centralized traffic control (CTC) systems to control train movements. Using CTC, a train dispatcher could align track switches anywhere on the territory so that trains could move into and out of sidings without having to stop and hand throw switches. The train dispatcher could also control the trackside signals governing the movement of trains. Two-way radios enabled train dispatchers to communicate directly with train and engine crews. These capabilities eliminated the need for most train orders, but still required the oversight of a train dispatcher.