With an average occurrence of 5 bridge strikes a day, hauliers across the UK face losses of millions of pounds a year. Ensuring that drivers know their HGV height limit and plan routes accordingly therefore has to be a priority for the industry.

Are you HGV height aware?

A driver should always know their HGV height (including load) and must remain vigilant about any changes to the height which can vary significantly depending on the load being carried. Vehicle height can change each time a vehicle is loaded, unloaded and reloaded.

The height of an HGV is calculated by measuring the overall travelling height (OTH) from the ground level of the vehicle, its equipment and its load. When drawing a trailer, the OTH is the measurement of the overall height of the vehicle and trailer combination, its equipment and load.

Road vehicles are generally less than 4.5m tall however there are instances where vehicle height exceeds this, notably when a tipper is raised or when a load protrudes above the top line of the vehicle.

Due to the height of most road bridges a vehicle and its load should not exceed a height of 5.03m. This is the normal maximum clearance under highway bridges in the UK.

There are instances where an HGV might be subjected to an effective reduction of the height clearance, notably where a road slopes down towards a bridge or other overhead obstruction. The clearance for HGV height may also change with the raising or lowering of the mid-lift axle.

In addition, changes to the level of a driving surface, for example where a road has been resurfaced, may affect clearance of an overhead obstruction.

HGV height indicators

Since 1st October 1997 the law states that HGV height must be indicated inside the cab of a vehicle if the overall travelling height (OTH) of the vehicle or trailer exceeds three metres. This should be done using an HGV height indicator. A height indicator for an HGV must:

• be where it can be easily read by the driver. Numbers must be at least 40mm high
• indicate the overall travelling height, with a tolerance of plus 150mm
• be in feet and inches or both feet and inches plus metres (but not in metres alone)
• be clear with no other letters, number or notices that could be confused with the height indicator

A driver is committing an offence if the vehicle OTH is greater than three metres high and the correct maximum height is not displayed in the cab. The maximum fine for being stopped without a height indicator in the cab is a £30 fixed penalty fine for the driver.

In-cab height indicators can be bought online however most vehicles tend to have them included by the manufacturer.

Checking the HGV height indicator should be included in the daily walkaround check that is carried out by a vehicle driver. Check out our handy article here.

HGV height changes

If an articulated lorry is pulling a trailer and the trailer is switched during a journey, the OTH may need to be recalculated as follows:

• Where the height variation is <150mm cab notices can be standardised at the overall height of the highest vehicle/trailer combination (i.e. where no combination will be greater than 150mm lower than the indicated height
• Where the height variation is >150mm cab notices will need to be adjusted accordingly and drivers will need a simple method for determining the height to be indicated on the cab notice

HGV height indicator chart

As previously mentioned, the overall travelling height of a vehicle and its load may vary throughout a job as the load is changed. In order to convert measured height MHF (UK) Ltd has created a handy conversion chart which you can download here:

HGV height limits and bridge strikes

Any HGV driver or operator would agree that bridge strikes by vehicles should be avoided for a number of reasons. Bridge strikes are costly, dangerous and not to mention inconvenient for other road users.

Most bridge strikes occur where roads pass under railway bridges.

But how can bridge strikes be avoided? Simply put, the easiest way to avoid bridge strikes is to ensure that a driver is made aware of and is constantly reminded of the height of their HGV.

The height indicator displayed in the cab of an HGV should always be checked and routes planned in advance.

Furthermore, drivers should be made aware of road signs and what they mean – if a vehicle is higher than shown on a circular (prohibition) traffic sign, the sign should not be passed. You would be very likely to collide with a bridge and be prosecuted.

Are you one of the 32% of HGV drivers who doesn’t know your vehicle’s height?

Research conducted by Network Rail found that lack of knowledge was the most common cause of bridge strikes in the UK.

• 32% of drivers don’t know their vehicle height
• 8% of drivers don’t believe road signage
• 9% of drivers report inadequate signage
• 11% of drivers reported poor information about low bridges when planning a route
• 22% of drivers reported poor route planning
• 15% didn’t understand signage
• 3% other

In the UK, those responsible for causing a strike are liable for meeting the costs associated with the strike. And with an average cost per bridge strike of £13,500, drivers and operators should take every step possible to ensure their HGVs don’t cause strikes.

Where an HGV strikes a bridge, the DVSA will investigate the company involved and both driver and operator could face criminal prosecution.

Network Rail and the UK Government has published a useful guide to the prevention of bridge strikes, which can be viewed here.