Low clearance

What it means

This sign warns of a structure ahead whose vertical opening is lower than the road's standard, and it states the measured clearance so drivers of tall vehicles can judge whether they fit. It matters overwhelmingly to vans, box trucks, vehicles with roof boxes, campers and anything on a trailer. A passenger car passes under without thinking about it, which is exactly why drivers of ordinary cars switch off around the sign, and why a rental van or a loaded roof rack meets the beam instead.

How it gets misread

The frequent misread is comparing your vehicle's nominal height to the stated clearance without margin, ignoring roof racks, aerials, air-conditioning units and suspension bounce. Another is assuming the clearance is measured at the centre of the opening when road crown can lower it at the edges.

What to do

If you drive anything taller than a sedan, know your real height including everything on the roof, and compare it to the signed figure with a margin. If in doubt, do not attempt it; turn and route around. Never test a marginal clearance at speed, because the structure always wins and the damage is to your roof and the bridge deck alike.

More warning signs

• Added lane →
• Advisory curve speed →

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