An HGV driver cannot treat a restriction sign as a last-second warning. By the time a low bridge, narrow road or weight limit is directly ahead, turning a large vehicle around may be difficult or unsafe. You need to recognise the sign quickly, know the vehicle’s dimensions and plan a suitable route before reaching the restriction.
This guide covers the UK signs most relevant to the height, width and weight of goods vehicles. It is an independent revision guide, so always use current official signs and instructions when driving.
Start with shape and colour
Three basic sign families make the meaning easier to predict:
- Red circles give prohibitions. They tell you what must not proceed, such as a vehicle over a displayed height, width or weight.
- Red triangles warn. They alert you to a hazard ahead, including restricted headroom at some bridges.
- Rectangles give information or directions. They may show an alternative route, the location of a restriction or additional details.
There are exceptions in the wider road-sign system, but this circle–triangle–rectangle rule is a strong starting point. Read the general guide to UK road-sign shapes and colours before learning the HGV-specific details below.
4.5 mHeight
2.3 mWidth
Height restriction signs
A red circular height sign means that vehicles over the height shown must not pass. The limit may be displayed in metric and imperial measurements. At a non-arch bridge, a mandatory red roundel may appear on the bridge and beside the road before it.
A triangular height sign warns of maximum headroom under a bridge or overhead obstruction. At an arch bridge, the available headroom can vary across the opening, so road markings and signs may guide high vehicles through the safest part. Never assume the centre is safe without reading all the signs and markings.
Official guidance says bridges with clearance below 16 feet 6 inches—about five metres—are normally signed. Drivers should still know the actual travelling height of the complete vehicle because loads, trailers, lifting equipment and suspension can affect it.
Before starting the journey
- Confirm the maximum travelling height of the vehicle, trailer and load.
- Check that the cab height indicator shows the correct figure where required.
- Plan a route suitable for that height, using information intended for commercial vehicles.
- Allow for route changes, temporary works and diversions.
- Do not rely blindly on a car sat-nav.
Vehicles over three metres high must display the overall height in the cab. If the vehicle or load changes, the displayed height must be checked rather than copied from a previous journey.
If you are unsure at a bridge
Stop safely before the restriction and obtain reliable information. Do not continue because another lorry appears to have passed, and do not rely on memory. If a warning system activates, follow its instruction. A bridge strike can kill or seriously injure road and rail users, damage the vehicle and infrastructure, and lead to regulatory action.
Width restriction signs
A red circular width sign prohibits vehicles wider than the measurement shown. The figure refers to the permitted maximum width at that point, so the driver must know the vehicle’s complete width, including relevant load projection and equipment.
A width restriction may protect a narrow bridge, street, temporary work area or physical narrowing. Even when the vehicle is technically below the signed limit, consider mirrors, bends, oncoming traffic and the space needed by a long trailer. Passing the sign does not guarantee that every later manoeuvre will be easy.
Advance signs may offer an alternative route. Make the route decision early instead of reaching the restriction and attempting an unsafe reverse or turn.
Maximum gross weight signs
A red circular sign containing a weight, such as “7.5 t”, indicates a maximum weight restriction. It may be used where heavier vehicles could damage a structure or where traffic is restricted for environmental reasons.
Do not guess from the fact that the vehicle is empty. Restrictions and their accompanying plates can apply in different ways, and enforcement may depend on the type of restriction. Know the vehicle’s plated weights, actual operating weight and route. If a plate provides an exception—for access, loading or a particular vehicle class—read the complete wording before deciding it applies to you.
Axle-weight restriction signs
An axle-weight restriction uses a red circle and a weight figure associated with an axle symbol or wording. It limits the weight transmitted by an axle, rather than simply the whole vehicle’s gross weight.
This matters because a vehicle can be within its total permitted weight yet still have poor load distribution. Loading too much weight over one axle can affect legality, tyres, braking, steering and stability. A correct total does not excuse an overloaded axle.
Goods-vehicle restriction signs
A red circular sign showing a lorry can prohibit goods vehicles. A weight figure may appear with the vehicle symbol, and an accompanying plate may describe the exact restriction or an exception such as access.
The important revision point is to read the whole sign assembly:
- the symbol identifies the vehicle class;
- the number may set a weight threshold;
- the plate may set times, access conditions or other exceptions; and
- advance direction signs may show the correct alternative route.
“Except for access” is not permission to use a road as a shortcut. It generally concerns reaching premises within the restricted area. If your destination is outside that area, follow the signed lorry route.
Length restrictions
A red circular sign can also prohibit vehicles or combinations over the length shown. Long vehicles may be unsuitable because of tight bends, narrow approaches, junction geometry or limited turning space.
Remember that the overall combination includes the trailer and relevant load. A route suitable for a rigid vehicle may not be suitable for an articulated combination, even if their weights are similar.
Five common test traps
- Confusing a warning with a prohibition. A triangle warns; a red roundel imposes a restriction.
- Checking the tractor unit but not the complete combination. Use the travelling dimensions of the entire vehicle and load.
- Assuming an empty lorry is exempt from a weight sign. Read the restriction and any plate; never assume.
- Ignoring advance signs. They allow a safe route change before the physical restriction.
- Following a car navigation route. Route information must account for commercial-vehicle dimensions and restrictions.
A practical pre-journey restriction checklist
- What are the vehicle’s travelling height, width, length and weight?
- Are the load and equipment included in those figures?
- Is the height indicator correct?
- Are there low bridges, weak bridges, weight limits or unsuitable roads?
- Are there temporary restrictions or diversions?
- Where is the safe alternative route?
- What will you do if the planned road becomes unavailable?
Original knowledge-check questions
1. A red circular sign displays “4.4 m”. What is the safest interpretation?
Vehicles over the displayed height must not proceed. Compare the sign with the confirmed travelling height of the complete vehicle.
2. Why can an axle-weight restriction matter when the total vehicle weight is legal?
Because poor load distribution can place too much weight on one axle even when the overall total is within its limit.
3. A lorry restriction has an “Except for access” plate. Can it be used as a through route?
Do not treat the exception as permission for through travel. Use it only when the stated access condition genuinely applies.
4. What should you do if the vehicle’s travelling height cannot be confirmed before a low bridge?
Stop safely before the restriction and obtain reliable information. Do not continue on an assumption.
These are original revision examples, not official DVSA questions.
Use the channel’s full road-sign test after reading this guide. Pause before each answer and note which restriction families still cause mistakes.
Watch the UK road-sign practice testOfficial sources
- GOV.UK: Low bridge signs
- GOV.UK: The signing system
- GOV.UK: Bridge strike guidance
- GOV.UK: Guide to maintaining roadworthiness
This independent guide is not affiliated with or endorsed by DVSA. Signs, restrictions and legal requirements can change. Follow the signs on the road and check current official guidance.
Comments
Post a Comment