Railway traffic control is a means of regulating railway movements through remote operation of signals and switches.
The first systematic attempt to control traffic on a large scale occurred on the railway lines after the use of trains became widespread. In order to maintain safe intervals between trains heading in the same direction, some form of regulation was needed. The block system was developed as a way to let train operators learn about track conditions prior to entry into different “blocks.” A portion of the track (blocks was controlled by a signalman who communicated to other block signalmen by telegraph. This would allow the train operators to access information on track conditions as the moved from block to block.
Colour light signals were a way to reduce human error and allow traffic to run more smoothly. Electric relays in the track would automatically activate the colour light signals.
Today’s modern invention of the moving-block system allows electric equipment to automatically adjust the speed of the train when it enters the zone of another train.