interlocking

Interlocking in railroads is a safety system that prevents trains from conflicting routes. It ensures that a clear signal is not displayed for one path if another train is already on a conflicting route. Early interlocking systems were developed in France and Britain in the mid-1850s. Modern systems use electrical relays and, increasingly, computer-based technology for route-setting and interlocking. These systems allow a single operator to set up a complete route through complex track areas by using control panels. Safeguards against malfunctions are achieved through duplication or triplication of computer systems to ensure accuracy before setting a route.1