The road narrows on the left warning sign shows an inward-sloping line on the left side with a straight line on the right inside a red triangle.
It warns that space on the left side of the road narrows ahead, which impacts drivers in the left lane or kerbside space.
What this sign means
The sign warns motorists that the left boundary of the road tapers inward, reducing width.
- Red warning triangle
- Inward slanting left line with straight right line
- Alerts to narrowing kerbs, hard shoulders, or left lanes
What to do when you see it
Check your mirrors and move towards the centre of the road safely if necessary, giving space to obstructions on the left.
- Adjust speed before reaching the taper
- Watch out for cyclists and pedestrians near the narrowed kerb
- Allow merging room for traffic on your left
How this sign is tested
DVSA theory questions assess your knowledge of road positioning, mirror routines, and courteous lane merging.
Common mistakes
Drifting into adjacent lanes without checking mirrors and blind spots first.
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
Does this sign mean the road becomes one-way?
No, it simply indicates that the carriageway becomes narrower on the left side.
Should I indicate before moving right to clear a left-hand restriction?
Yes, use signals if changing lanes or if your manoeuvre will benefit other road users.
Are these signs common in roadwork zones?
Yes, temporary yellow or standard red warning signs frequently highlight left-lane narrowings.