Keep left and no through road signs explained
Updated •4 min read
The keep left sign is a blue circle sign that tells you to keep to the left of it; "No through road for vehicles" warns that the road ahead is a dead end. Both names are from the Highway Code's traffic signs page on gov.uk, read on 28 October 2026: "Keep left (right if symbol reversed)" and "No through road for vehicles".
Keep left (and turn left ahead)
The Highway Code lists "Keep left (right if symbol reversed)" under signs with blue circles but no red border, which it says "mostly give positive instruction". Beside it are "Ahead only", "Turn left ahead (right if symbol reversed)", "Turn left (right if symbol reversed)" and "Vehicles may pass either side to reach same destination".
| Sign | Highway Code name | What to do |
|---|---|---|
| Keep left | "Keep left (right if symbol reversed)" | Pass on the left of the sign |
| Turn left ahead | "Turn left ahead (right if symbol reversed)" | Turn left at the junction ahead |
| Turn left | "Turn left (right if symbol reversed)" | Turn left here |
| Pass either side | "Vehicles may pass either side to reach same destination" | Either side is allowed |
Worked example. A question shows a blue circle with an arrow and asks what it means. A blue circle with no red border gives an instruction, so it is not a warning. Match the arrow to the caption: keep left, turn left ahead or turn left. "Turn left ahead" means the turn comes at the junction ahead. Our pass either side guide covers the two-arrow sign.
No through road
The Highway Code lists "No through road for vehicles" under information signs. It means the road does not lead through to anywhere else for vehicles.
On a theory test the answer is the plain one: the road is a dead end for vehicles. Do not confuse it with a "no entry" sign: the caption says the road has no way through, not that you may not enter.
How to tell them apart
- Colour and border. Blue circle, no red border: an instruction. Red circle: mostly prohibitive. Triangle: mostly a warning (Highway Code, traffic signs).
- Arrows. One arrow gives an instruction such as keep left or turn left. Two arrows apart mean either side is allowed.
- Wording. If the sign carries words, such as "No through road", read them first.
- Plates. The Highway Code says plates below signs qualify their message, so read any plate under a sign before you answer. It lists the signs in groups: orders, warnings, directions, information and road works.
Our road signs guide and dual carriageway ends sign guide explain more shapes. On a roadworks vehicle, keep left and right signs mean you must pass on the side shown, as in our roadworks guide.
Practise signs
See every official picture in the sign list, then try the free practice questions. theorytest.ai is independent and is not affiliated with the DVSA.
Frequently asked questions
What does the keep left sign mean?
It is a blue circle sign and means keep to the left of the sign. The Highway Code calls it "Keep left (right if symbol reversed)".
What does the turn left ahead sign mean?
It is "Turn left ahead (right if symbol reversed)": the turn is at the junction ahead, not where you are.
What does the no through road sign mean?
"No through road for vehicles": the road ahead is a dead end for vehicles.
Is no through road the same as no entry?
No. No through road warns the road ends. It does not stop you entering.