Maximum Height vs Maximum Width: What’s the Difference?
When you’re revising road signs for the UK driving theory test, it’s easy to confuse Maximum Height and Maximum Width restrictions. Both signs are circular, both use black symbols on a white background with a red border, and both show measurements. But they control very different things.
Here’s how to tell them apart.
Maximum Height Restriction
- What it looks like: A red circle with two vertical arrows (one pointing up, one pointing down) and a measurement (e.g. 4.4m or 14’6”).
- What it means: Vehicles taller than the stated height are not allowed beyond this point.
- Why: Often used before bridges, tunnels, or underpasses where taller vehicles risk collision.
Tip for pupils: The up and down arrows tell you it’s about height – TOP to BOTTOM
Maximum Width Restriction
- What it looks like: A red circle with two horizontal arrows (pointing left and right) and a measurement (e.g. 2.0m).
- What it means: Vehicles wider than the stated width cannot pass.
- Why: Used at narrow bridges, lanes, or gateways where larger vehicles could get stuck or cause danger.
Tip for pupils: The side-to-side arrows tell you it’s about width.
Quick Memory Trick
- Vertical arrows = Height
- Horizontal arrows = Width
Or as I like to phrase it to learners:
“Arrows pointing up and down = watch your roof.
Arrows pointing side to side = watch your doors.”
Why Learners Must Know This
Getting these mixed up in the theory test is an easy way to drop a mark. On the road, misunderstanding could mean driving a tall van under a low bridge, or steering a wide car into a gap it can’t squeeze through — both of which are dangerous and costly mistakes.
Maximum Height vs Maximum Width: What’s the Difference?
Remember: the arrows tell the story. Up and down = maximum height. Side to side = maximum width. Spot the difference, and you’ll never mix them up again.