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  2. North American railroad signals - Wikipedia

    en.wikipedia.org/.../North_American_railroad_signals

    A Pennsylvania Railroad high signal displaying Approach Medium Amtrak colorized position lights at Trenton, New Jersey. Position light signals use rows of 5 + 3 ⁄ 8-inch-diameter (140 mm) lamps to simulate the positions of an upper quadrant semaphore blade.

  3. Railway signalling - Wikipedia

    en.wikipedia.org/wiki/Railway_signalling

    In the very early days of railway signalling, the first coloured lights (associated with the turned signals above) presented a white light for 'clear' and a red light for 'danger'. Green was originally used to indicate 'caution' but fell out of use when the time interval system was discontinued.

  4. Railway signal - Wikipedia

    en.wikipedia.org/wiki/Railway_signal

    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. In many countries, small position light signals are used as shunting signals, while the main signals are of colour light form.

  5. North American railroad signaling - Wikipedia

    en.wikipedia.org/wiki/North_American_railroad...

    Signal aspect and indication illustrations instead appear in each railroad's system special instructions or operating timetable for the region or division where the aspects and indications apply. This practice is necessary due to the lack of uniformity in aspects between the multitude of railroads participating in GCOR, which includes a number ...

  6. Railway semaphore signal - Wikipedia

    en.wikipedia.org/wiki/Railway_semaphore_signal

    Later signals using electric lamps used green lenses. Some signals converted to electric lamps from oil, used a yellow-tinted bulb with the original blue lens to maintain the correct colour or from 1996 on the Western Region of British Railways, a 12-volt 5-watt bulb was fitted but fed at 10.7 volts to produce a brilliance approximating to the ...

  7. UK railway signalling - Wikipedia

    en.wikipedia.org/wiki/UK_railway_signalling

    Clearing sequence from red to green of a 4 aspect colour light signal. In total, colour-light signals in the UK display seven aspects. These are: Green – Clear. The train may proceed subject to any speed restrictions applying to the section of line or to the train itself. (See also Flashing Green below.) Double yellow – Preliminary caution ...

  8. Traffic light - Wikipedia

    en.wikipedia.org/wiki/Traffic_light

    Railroad signals, for stopping trains in their own right of way, generally use the opposite positioning of the colours; that is, for signals above the driver's eyeline, green on top and red below is the standard placement of the signal colours on railroad tracks. There are three reasons for this variation: there is no risk that railway signals ...

  9. Signaling of the New York City Subway - Wikipedia

    en.wikipedia.org/wiki/Signaling_of_the_New_York...

    Common automatic and approach signals consist of one signal head showing one of the following signal aspects: stop (one red light); with special rules for call-on and timer signals [1]: 110–111 [7]: 68 clear, next signal at clear or caution (one green light) [1]: 110–111 [7]: 68