If a vehicle and its load are too big or too heavy to travel under standard road rules, the movement is classed as an abnormal load. These jobs need specialist trailers, careful route planning and, in many cases, notice to the police and highway authorities. This guide explains the UK thresholds in plain terms so you know what you are dealing with.
The three thresholds that make a load “abnormal”
A load is treated as abnormal when it exceeds one or more of the limits set out in the Road Vehicles (Construction and Use) Regulations 1986. In practice, a movement becomes abnormal once it goes over any of the following:
- Weight over 44,000kg (44 tonnes) gross
- Width over 2.9 metres
- Rigid length over 18.65 metres
The key word is indivisible. An abnormal load is usually one that cannot reasonably be split into smaller parts for transport, such as a single piece of plant, a steel beam or a large tank. If the load could simply be broken down and carried on standard lorries, the special rules generally do not apply.
C&U versus STGO: two sets of rules
Two regulations govern these movements. The Construction and Use (C&U) Regulations cover vehicles operating within standard limits. Once a load goes beyond what C&U allows, the movement falls under the Road Vehicles (Authorisation of Special Types) (General) Order 2003, known as STGO. STGO permits heavier and larger combinations than normal, provided the operator follows its conditions.
The three STGO weight categories
| Category | Max gross weight | Min axles | Motorway speed |
|---|---|---|---|
| STGO 1 | Up to 50,000kg | 5 | 60 mph |
| STGO 2 | Up to 80,000kg | 6 | 40 mph |
| STGO 3 | Up to 150,000kg | 6 | 40 mph |
STGO 2 and 3 vehicles also carry lower speed limits on dual carriageways (35 mph) and other roads (30 mph), which is one reason heavy abnormal moves take longer to plan and complete than standard deliveries.
What an abnormal load means in practice
Moving an abnormal load is not simply a case of loading and driving. Depending on the dimensions and weight, the operator may need to:
- Notify the police and highway and bridge authorities in advance (often two clear days’ notice, more for the heaviest loads)
- Plan a route that avoids weak bridges, low structures and tight junctions
- Display marker boards and, for wider loads, fit side markers and lights
- Arrange escort vehicles for the widest, longest or heaviest movements
Loads over 3 metres wide normally require attendants or escorts, and loads over 5 metres wide trigger additional written notice to National Highways. The exact requirements scale up with the size of the load, which is why early planning matters.
What about height?
You will notice height is not in the list of legal abnormal-load thresholds. There is no single maximum height for vehicles on UK roads, but in practice anything over about 4.95 metres (16ft 3in) must be planned carefully, because that is the point at which the driver is required to carry a notice of the travelling height in the cab and check the route for low bridges and structures. Many overheight loads are perfectly legal but still need a surveyed route, which is why height should always be declared to your haulier even though it does not, on its own, make a load “abnormal”.
Common examples of abnormal loads
Typical abnormal loads include excavators and crawler cranes, portable cabins and modular buildings, large industrial tanks and silos, transformers, boats, and structural steelwork. Anything that is wide, long, tall or simply very heavy tends to fall into this category.
Why the rules exist
It is easy to see the notifications and speed limits as red tape, but they exist for good reasons. A heavy load concentrates enormous force on bridges and road surfaces, and a wide one needs careful handling past oncoming traffic, parked cars and street furniture. By telling the authorities in advance, the operator gives them the chance to check the route is genuinely safe and to flag anything – a weak bridge, roadworks, a tight roundabout – that could turn a routine job into an incident. Getting it right protects your load, the public and the road network alike.
Get the move planned properly
If you are not sure whether your load is abnormal, it is worth checking before you book transport, as the notifications and route planning take time. Northampton Road Haulage handles oversized and abnormal load movements across the UK and can advise on categories, notice periods and the right trailer. Call us on 01604 385213 for a no-obligation chat.