A signalman is a railroad worker who operates line signals in order to monitor and adjust the movement of trains. Traditionally, signalmen used flags and bell signals to alert drivers and other railroad personnel regarding advancement on the track. Modern computer and communications technology has allowed the automation of many signaling systems; however, many train lines still rely on skilled signalmen to correctly operate these systems and provide oversight in case of system failures.
Railway signals are vital to train movement, as they guard the flow of railway traffic and can alert oncoming drivers to dangers ahead. With many trains running on coinciding tracks, a monitoring system is essential to preventing collisions and accidents. Signals are often lights or mechanical signposts that operate like traffic lights on roads; by changing a signal from green to red, a signalman can tell an oncoming train to stop and wait until the light is changed back to green.
In the early days of train travel, the signalman shared many duties with a station operator, and carefully tracked the timing and movement of each train to ensure that collisions were avoided. Some would run entire stations, selling tickets and managing freight loading of each train. Early signal workers used colored flags to grab the attention of drivers, alerting them to rail conditions. With the development of the telegraph, communication between signal points became greatly enhanced, allowing more accurate traffic control between stations and signal boxes.
Later developments, such as the telephone, computer technology, in-ground sensors in the tracks, and even cell phones, all helped to improve the communication abilities of signalers. Many moderns train systems are run on automated systems, which can use both sensor data and user-input to track each train on a computer model of the line. Yet even with the technological advances, the role of the signalman is still vital in railroad operation; much like air traffic controllers, these travel supervisors must be able to understand and maintain automated systems as well as maintain the train system manually should equipment fail.
The essential and difficult job of the signaler has not escaped the romance of fiction. In an 1866 ghost story by Charles Dickens, a signalman receives spooky bell signals from a ghostly presence that warn of tragic accidents. Even comic books prove fertile ground for the power of this vital position; several Batman comics track a gangster fascinated by the power of signs and signals who eventually becomes the terrorizing super villain, the Signalman.