Low bridge signs and your roof tent's travelling height
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A roof tent changes the vehicle you drive into a car park, under a bridge or through a campsite entrance. Use a measured travelling height, not the brochure figure, and know what the signs on the road mean. To take the measurement itself, follow the loaded height measurement guide.
What the signs mean
The Department for Transport's guidance, which covers England, Scotland and Wales, separates two kinds of sign:
- Mandatory (regulatory) signs at non-arch bridges. The DfT page says it is unlawful for an overheight vehicle to pass one of these. They show the height in metric and imperial units, and appear on the bridge and at the roadside before it. Advance signs warn that a mandatory restriction is ahead.
- Warning signs. A triangular sign gives the maximum headroom in metric and imperial units, and may sit well ahead of the bridge with a plate showing the distance in yards or miles.
At arch bridges the triangle shows the maximum safe headroom, with chord markings to show where different headroom applies across the arch. DfT says road markings guide high vehicles through the highest part of the arch, and that drivers of all vehicles should give way to oncoming high vehicles when there is not room to pass in the middle of the road. A plate below a triangle can warn of an overhanging building or structure, and black and yellow bands may be added to make a bridge more visible.
Some high-risk bridges have a variable message sign that flashes four amber lights, the top pair alternating with the bottom pair, when a high vehicle breaks an infrared beam. If you see it, treat it as a warning about your own vehicle.
DfT says bridges with a clearance under 16 ft 6 in (about 5 m) are normally signed, and that some older restrictions show imperial units only. Keep a reliable conversion to hand, and do not round your vehicle height down to make a comparison look acceptable. If your measured height is uncertain, resolve the clearance rather than testing it by approaching closer.
Check the places the route planner misses
Ask campsites about entrance barriers, covered areas and the route to the allocated pitch, and give them your measured height. Check parking at towns and attractions you plan to visit. A general statement that cars are welcome does not describe your altered height. The campsite booking checklist has the other arrival questions.
Keep the reply with the booking. A photograph of an open entrance does not confirm the clearance on every later section.
Keep a height card in the car
- Travelling height, units and date measured.
- What was fitted when you measured: bars, tent, box, accessories.
- The conversion between metric and imperial, if you use both.
- Any booking replies about low entrances.
Recheck after changing racks, adding equipment or using a different vehicle. If a diversion takes you somewhere unfamiliar, stop safely and resolve the route before continuing. A route checked beforehand does not clear every alternative.
Height is one check of several
Height, vehicle mass and roof load are separate questions. Use the roof tent compatibility checklist for the load documents, and the tent and box together guide if a box shares the roof. Passing one check does not settle the others.
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