Hazard warning line: what it means
Longer white dashes with shorter gaps warn of a hazard ahead. Cross only if the road is clear and you intend to overtake or turn off.
What does the hazard warning line mean?
When the white dashes in a centre line become longer and the gaps shorter, they warn of a hazard ahead. Rule 127 says not to cross unless you can see the road is clear and want to overtake or turn off.
Know your traffic signs says a hazard warning line can replace a centre line or lane line. It is also used on approaches to junctions.
Quick quiz
What does the picture at the top of this page show?
- The line nearer to you decides if you may cross.
- Diagonal stripes that separate traffic.
- Long white dashes warn of a hazard ahead.
Show answer
C. Long white dashes warn of a hazard ahead. Longer white dashes and shorter gaps in the centre line mean there is a hazard ahead (The Highway Code, rule 127). Source: Know your traffic signs: road markings, GOV.UK; The Highway Code, rule 127, GOV.UK
Where will you see it?
In place of a centre line or lane line, including on the approach to a junction. An upright sign may identify the hazard, such as a bend.
What should you do?
Do not cross the centre line unless you can see the road is clear and want to overtake or turn off.
What do people get wrong?
A broken line does not mean you can cross without checking. The longer dashes warn of a hazard, and rule 127 sets conditions for crossing.
Common questions
What do long white dashes in the middle of the road mean?
When the dashes lengthen and the gaps shorten, there is a hazard ahead. This is explained in rule 127.
Can I cross a hazard warning line?
Rule 127 says not to cross the centre line unless you can see the road is clear and wish to overtake or turn off.
Compare with
Double white linesThe line nearer to you decides if you may cross.
Hatched markingsDiagonal stripes that separate traffic.
Want to test someone else? Play a road-sign quiz with friends and family.
Sources
Checked on 5 November 2026 against Know your traffic signs (road markings) and The Highway Code rule 127.
Contains public sector information licensed under the Open Government Licence v3.0. The diagram is our own simplified drawing, not to scale. Sources and image credits.