Usually, signals and other equipment (such as track circuits and level crossing equipment), are powered from a low voltage supply (varies with country and equipment). The reason behind this is that the low voltage allows easy operation from storage batteries Continue reading “Railway Signalling power”
Some locomotives are equipped to display cab signals. These can display signal indications through patterns of lights in the locomotive cab, or in simple systems merely produce an audible sound to warn the driver of a restrictive aspect. Occasionally, cab signals are used by themselves, but more commonly they are used to supplement signals placed at lineside. Continue reading “Cab signalling for Railway”
Originally, signals displayed simple stop/proceed indications. As traffic density increased, this proved to be too limiting, and refinements were added. One such refinement was the addition of distant signals on the approach to stop signals. The distant signal gave the driver/engineer warning that he was approaching a signal which might require a stop. Continue reading “Control and operation of signals for Railway”
Lineside signals need to be mounted in proximity to the track which they control.
When a single track is involved, the signal is normally mounted on a post which displays the arm or signal head at some height above the track, in order to allow it to be seen at a distance. Continue reading “Signal mounting of Railway”
A system combining aspects of the color and position systems was developed on the Baltimore and Ohio Railroad in the 1920s and was also applied to the Chicago and Alton Railroad when the latter was under B&O control. The CPLs were first installed as a pilot on the Staten Island Railroad in New York City, a former B&O subsidiary later turned rapid transit line operated by the Metropolitan Transportation Authority. Continue reading “Railway Color-position signals”
A position light signal is one where the position of the lights, rather than their colour, determines the meaning. The aspect consists solely of a pattern of illuminated lights, which are all of the same colour (typically amber or white). In many countries, small position light signals are used as shunting signals, while the main signals are of color light form. Also, many tramway systems (such as the Metro of Wolverhampton) use position light signals. Continue reading “Railway Position light signals”
The introduction of electric light bulbs made it possible to produce color light signals which were bright enough to be seen during daylight. Many railroads thus converted to color light signals.
The signal head is the portion of a color light signal which displays the aspects. To display a larger number of indications, a single signal might have multiple signal heads. Some systems used a single head coupled with auxiliary lights to modify the basic aspect. Continue reading “Railway Color light signals”
The oldest forms of signal displayed their different indications by a part of the signal being physically moved. The earliest types comprised a board that was either turned face-on and fully visible to the driver, or rotated away so as to be practically invisible. These signals had two or at most three positions. Continue reading “Railway Mechanical signals”
Signals have aspects and indications. The aspect is the visual appearance of the signal; the indication is the meaning. In American practice the indications have conventional names, so that for instance “Medium Approach” means “Proceed at not exceeding medium speed prepared to stop at next signal”. Different railroads historically assigned different meanings to the same aspect, so it is common as a result of mergers to find that different divisions of a modern railroad may have different rules governing the interpretation of signal aspects. Continue reading “Railway Signal Aspects and Indications”
Signals are used to indicate one or more of the following:
- that the line ahead is clear (free of any obstruction) or blocked.
- that the driver has permission to proceed.
- that points (also called switch or turnout in the US) are set correctly.
- which way points are set. Continue reading “Application and positioning of railway signals”
A signal is a mechanical or electrical device erected beside a railway line to pass information relating to the state of the line ahead to train drivers/engineers. The driver interprets the signal’s indication and acts accordingly. Continue reading “What is Railway Signal?”