Double white lines painted along the centre of the road are used to separate opposing traffic flows on single carriageways.
The rules governing double white lines depend on whether the line nearest to your vehicle is solid or broken.
What this sign means
When the line nearest to you is solid, you must not cross or straddle it unless specific legal exceptions apply.
If the line nearest to you is broken, you may cross it to overtake if it is safe and the road ahead is clear.
- Solid line nearest you: Do not cross or straddle except for narrow exceptions.
- Broken line nearest you: Overtaking allowed if clear and safe.
- Double solid lines: Strictly no crossing or straddling for both lanes.
What to do when you see it
Keep to your side of the road when the solid line is on your side. Do not cross to overtake slower traffic unless an exception applies.
You may cross a solid line to pass a stationary vehicle, pedal cycle, horse rider, or road maintenance vehicle travelling at 10 mph or less.
How this sign is tested
Theory tests frequently ask about the exact conditions allowing a driver to cross a solid double white line.
On practical tests, straddling or crossing a solid line unnecessarily will result in a serious fault.
Common mistakes
Crossing a solid double white line to overtake a vehicle travelling at 15–20 mph is illegal but widely misunderstood.
Drivers also fail to return to their lane early enough when a broken line changes into a continuous solid line.
Test yourself on this one
Road and traffic signs is the biggest category in the question bank with 102 questions, and signs turn up inside other categories too. Work through them free, no sign-up needed.
Practise road sign questionsFrequently asked questions
Can I overtake a cyclist on double solid white lines?
Yes, but only if the cyclist is travelling at 10 mph or less and it is completely safe to do so.
Can I turn right across a solid double white line?
Yes, you may cross a solid line to enter a side road, driveway, or premises.
Can I stop or park on a road marked with double white lines?
No, you must not park or pick up/drop off passengers along roads with double white lines, except to set down disabled passengers.