British four-aspect colour light signal

A colour light showing one of four aspects.

Also known as: Double yellow signal head, Multiple aspect signalling

Engineering & technicalRoad & transportStandard profile

Meanings

A British colour light signal capable of showing red, single yellow, double yellow or green, giving two warnings before a stop.

Officially standardisedVerified fact
Shows one of four aspects, red, single yellow, double yellow or green, on the British network.
Contexts: Public information
Officially standardisedVerified fact
Gives two warnings rather than one before a stop, which is what allows trains to run at intervals shorter than a single braking distance.
Contexts: Public information

A vertical head of four lamps, of which one shows at a time except in the double warning aspect where two show together.

IdentityHigh confidence: High confidence because the identity is defined by a current official standard.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is defined by a current official standard.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references.

GERT8000 Rule Book, Signals, handsignals, indicators and signs
Rail Safety and Standards Board (RSSB), Great Britain · retrieved 2026-08-24
The British national rule book module covering signals, indicators and lineside signs. Cited for a signal's identity and its defined meaning on the Great Britain network. Records are descriptive; the Rule Book itself is the operating authority and is not reproduced here.
Railway signalling
Wikipedia · retrieved 2026-08-23
Tertiary reference, cited for the conventional form of a marking or signal and where it is used. Where a national authority or standards body defines it, that source is cited alongside and governs.

Last reviewed 2026-08-25

Meanings

A British colour light signal capable of showing red, single yellow, double yellow or green, giving two warnings before a stop.

Officially standardisedVerified fact

Shows one of four aspects, red, single yellow, double yellow or green, on the British network.

Officially standardisedVerified fact

Gives two warnings rather than one before a stop, which is what allows trains to run at intervals shorter than a single braking distance.

Confidence

IdentityHigh confidence: High confidence because the identity is defined by a current official standard.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is defined by a current official standard.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references.

Sources

GERT8000 Rule Book, Signals, handsignals, indicators and signs
Rail Safety and Standards Board (RSSB), Great Britain · retrieved 2026-08-24
The British national rule book module covering signals, indicators and lineside signs. Cited for a signal's identity and its defined meaning on the Great Britain network. Records are descriptive; the Rule Book itself is the operating authority and is not reproduced here.
Railway signalling
Wikipedia · retrieved 2026-08-23
Tertiary reference, cited for the conventional form of a marking or signal and where it is used. Where a national authority or standards body defines it, that source is cited alongside and governs.

Last reviewed 2026-08-25