British semaphore distant signal

A fishtailed arm warning of the signal ahead.

Also known as: Fishtail signal arm, Notched semaphore arm, Warning arm

Engineering & technicalRoad & transportStandard profile

Meanings

A British semaphore whose notched, fishtail-ended arm warns that the next stop signal may be at danger, but does not itself require a stop.

Officially standardisedVerified fact
Warns that the stop signal ahead may be at danger, allowing a driver to begin braking before it comes into sight.
Contexts: Public information
Officially standardisedVerified fact
Never itself requires a stop, which is why the notch exists: a driver passing a fishtail at caution has not passed a signal at danger.
Contexts: Public information

An arm with a V-shaped notch cut into its outer end, giving the fishtail outline that names it.

Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references.
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.

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 semaphore whose notched, fishtail-ended arm warns that the next stop signal may be at danger, but does not itself require a stop.

Officially standardisedVerified fact

Warns that the stop signal ahead may be at danger, allowing a driver to begin braking before it comes into sight.

Officially standardisedVerified fact

Never itself requires a stop, which is why the notch exists: a driver passing a fishtail at caution has not passed a signal at danger.

Confidence

Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references.
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.

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