Information sign
Lane control ahead sign
What does the Lane control ahead sign mean?
Warns that lane control signals are in use on the road ahead. Watch the signals above each lane.
Also known as: Tidal flow ahead
What it means
Lane control signals are in use on the road ahead.
On some busy roads, lane control signals vary the number of lanes in each direction. This sign warns you before you reach them.
Special signs explain what the signals mean.
Where you'll see it
On the approach to roads with tidal flow lane control.
Rules to know
Lane control signals are used to vary the number of lanes available to give priority to the main traffic flow. Signs show lane control on the road ahead.
Know Your Traffic Signs, p. 142
Common mistakes
Mistake: Not looking up at the signals.
Instead: Each lane has its own signal. Follow the one above your lane.
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© Crown copyright. Free to reuse under the Open Government Licence v3.0, as long as the sign is reproduced accurately and not in a misleading context.
Related signs
Ends
End of lane control
Information sign
Shows where lane control ends.
See also
Lane open (green arrow)
Regulatory sign
One of the signals.
More information signs
All information signs
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- Know Your Traffic Signs (Department for Transport, Sixth edition, 2023), Tidal flow lane control signs and signals, p. 142
Sign image: Department for Transport, Traffic sign images (diagram 5012). © Crown copyright, reused under the Open Government Licence v3.0.
Last reviewed 11 October 2026. This page explains the sign in our own words; for the full rules, see The Highway Code. How we source and check content