Dual carriageway ahead sign: what it means
This blue sign tells you that a section of dual carriageway begins ahead. The two directions of traffic will be split by a central reservation.
What does the dual carriageway ahead sign mean?
Know your traffic signs describes it as a section of dual carriageway road beginning directly ahead. Other versions show the distance to the start.
Rule 137 says on a two-lane dual carriageway, stay in the left-hand lane and use the right-hand lane for overtaking or turning right.
Quick quiz
What does the sign at the top of this page mean?
- A dual carriageway starts ahead.
- The dual carriageway ends ahead.
- One lane ends ahead; the lanes reduce.
Show answer
A. A dual carriageway starts ahead. It tells you a dual carriageway begins ahead (Know your traffic signs). Source: Know your traffic signs: information signs, GOV.UK; The Highway Code, rule 137, GOV.UK; Traffic sign images, Department for Transport, GOV.UK
Where will you see it?
Before the start of a dual carriageway on a main road.
What should you do?
Keep left, and use the right-hand lane only to overtake or turn right.
What do people get wrong?
Staying in the right-hand lane after overtaking. Move back left when it is safe.
Common questions
Which lane should I use on a dual carriageway?
The left-hand lane. Use the right-hand lane for overtaking or turning right (rule 137).
What is the opposite sign?
The dual carriageway ends warning triangle tells you two-way traffic is ahead.
Compare with
Dual carriageway ends signThe dual carriageway ends ahead.
Lane ends ahead signOne lane ends ahead; the lanes reduce.
Want to test someone else? Play a road-sign quiz with friends and family.
Sources
Checked on 4 November 2026 against Know your traffic signs (information signs) and The Highway Code rule 137.
- Know your traffic signs: information signs, GOV.UK
- The Highway Code, rule 137, GOV.UK
- Traffic sign images, Department for Transport, GOV.UK
Contains public sector information licensed under the Open Government Licence v3.0. Traffic sign images are Crown copyright, from the Department for Transport. Sources and image credits.