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The figure in the cab

Height and bridges

A vehicle over three metres tall carries its height in the cab, where the driver can see it at every bridge, because the bridge will not move out of the way. This page sets out the rule and works out the figure for you.

A lorry approaching a low bridge, heights drawn to scale A rigid lorry measured at 4.15 metres approaches a bridge whose sign reads 14 feet 3 inches, 4.3 metres. The notice in its cab reads 13 feet 8 inches, 4.2 metres: never lower than the vehicle and no more than 150 millimetres above it. A dashed line carries the notice height under the bridge, with seven inches to spare. 13′ 8″ 4.2 M THE NOTICE IN THE CAB NEVER LOWER THAN THE VEHICLE, AT MOST 150 MM ABOVE IT 13′ 8″ IN THE CAB MEASURED 4.15 M SIGN 14′ 3″ · 4.3 M
Heights to scale, lengths not. A lorry measured at 4.15 m carries 13′ 8″ in the cab, and a bridge signed 14′ 3″ passes it with seven inches to spare.

The rule for the notice

Regulation 10 of the Road Vehicles (Construction and Use) Regulations 1986 says that a vehicle whose overall travelling height is more than three metres must show a notice in the cab, where the driver can read it, giving that height. The figure is shown in feet and inches, with numerals at least 40 mm tall, or in feet and inches together with metres.

The height on the notice may not be lower than the vehicle's real height, and it may not be more than 150 mm above it; the allowance is a metre for a vehicle carrying high-level equipment. Where both units are shown, the two figures may differ by no more than 50 mm. The full wording is on legislation.gov.uk.

Measuring the travelling height

The notice is only as good as the measurement behind it. The height is taken on level ground to the highest point of the vehicle as it travels: the top of the body, a raised roof, or the load itself on an open trailer. When the load or the body changes the height, the figure in the cab changes with it, before the vehicle moves.

Cab height notice

Type the measured travelling height; the figure for the notice comes out in feet and inches with its metric line, checked against regulation 10.

Measured in

13' 8"4.2 m

Over 3 m, so a notice in the cab is required. Show this figure in feet and inches, with the metric line if you use one.

  • Not lower than the vehicle: 16 mm above the measured height.
  • No more than 150 mm above it: 50 mm at most.
  • Feet-and-inches and metric within 50 mm of each other: 34 mm apart.

Feet and inches are rounded up to the next whole inch, so the notice is never lower than the vehicle. The metric line is rounded up to the nearest 10 cm, 5 cm or 1 cm, whichever keeps it within 50 mm of the imperial figure.

The view from inside an empty right-hand-drive lorry cab before dawn: a dual carriageway runs ahead across flat land and passes under a plain concrete road bridge, under a deep blue sky.
Read the sign, then the cabA bridge sign gives the clearance under it. The figure in the cab is what the driver compares it with, every time.

Close to home

East London has its own fixed heights. The northbound bore of the Blackwall Tunnel carries a 4.0 m height restriction, and the Silvertown Tunnel, opened on 7 April 2025, has a lane for buses and heavy goods vehicles. A route is planned against the measured height of the vehicle on the day, not against the height it usually is.

Speed limits for goods vehicles

For a goods vehicle over 7.5 tonnes in England and Wales the national limits are 50 mph on a single carriageway, 60 mph on a dual carriageway and 60 mph on a motorway, with 30 mph in built-up areas in England. Up to 7.5 tonnes the limits are 50, 60 and 70 mph, and 60 mph on a motorway when articulated or towing. A driver of a vehicle over 3.5 tonnes takes a break of at least 45 minutes after no more than four and a half hours of driving, and the plan for a long run allows for it. The current limits are on gov.uk.

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