Driver handbook control
Make the escalation route explicit
Your company procedure should state who to call, which details to report and when the vehicle must remain stopped.
Tailored guidanceWritten around your fleet and routesAsk about a handbook
Know the travelling height before the journey starts
Check the maximum height of the vehicle, trailer, load and equipment. The height can change when the trailer, load, fifth-wheel setting or mounted equipment changes. Do not rely on a figure remembered from another combination.
If the overall travelling height is over 3 metres, the correct maximum height must be displayed in the cab where it can easily be read. Check the notice before moving off and update it when the combination changes.
Official low-bridge signs
Images are official Department for Transport reproduction artwork. © Crown copyright, reproduced under the Open Government Licence v3.0.
Roundel and triangle are not the same instruction
A red-ring roundel gives an order. It is unlawful for an overheight vehicle to pass a mandatory height restriction. A warning triangle identifies the maximum headroom at the hazard.
At an arch bridge, the greatest clearance is through the marked part of the arch. Vehicle width matters because the signed height is not available across the whole opening.
What to do en route
- Read the full sign and any distance, direction or diversion plate.
- Compare the restriction with the current cab-height notice.
- Do not follow a route because another large vehicle used it.
- If a high-vehicle warning activates, do not continue towards the bridge.
- Stop only in a safe and lawful place, then contact the transport office for an alternative route.
If the height or route is uncertain
Do not guess. Tell the transport office your exact location, direction of travel, vehicle and trailer details, displayed height and the complete sign wording. Keep the vehicle away from the restriction until a safe route is confirmed.
Report an incorrect cab notice, unreadable height record or route conflict. The record should be corrected before the vehicle is sent out again.
