Guide
What counts as an abnormal load? Weights, widths and lengths
Updated
The first question on every heavy haulage enquiry is whether the movement is abnormal at all, because the answer changes who has to be told, how far in advance, and what the load may be carried on.
The thresholds
National Highways states that an abnormal load is a vehicle that has any of the following (nationalhighways.co.uk):
- a weight of more than 44,000kg;
- an axle load of more than 10,000kg for a single non-driving axle and 11,500kg for a single driving axle;
- a width of more than 2.9 metres;
- a rigid length of more than 18.65 metres.
Any one of them is enough. A relatively light machine that is 3.2 metres wide is an abnormal load just as surely as a 60 tonne press, and the width is often the trigger people miss when they measure a machine without its tracks, guarding or overhang.
Abnormal indivisible loads and the STGO categories
Most oversize movements run under the Road Vehicles (Authorisation of Special Types) (General) Order 2003, usually called STGO. The gov.uk special types enforcement guide defines an abnormal indivisible load as a load "which cannot be divided into 2 or more loads to be transported by road", and is blunt about the test: "a large load that can be easily divided in half by undoing a few bolts, must be split up for transport". Vehicles carrying such loads fall into three categories (gov.uk):
| Category | Weight and axles | Notice stated in the guide |
|---|---|---|
| Cat 1 | Up to 46,000kg with a minimum of 5 axles, or up to 50,000kg with a minimum of 6 axles | 2 working days to highway and bridge authorities about the weight; dimensions may need to be given to the police |
| Cat 2 | Not exceeding 80,000kg, minimum 6 axles, maximum axle weight 12,500kg | 2 working days to highway and bridge authorities in relation to weight; dimensions may need to be given to the police |
| Cat 3 | Not exceeding 150,000kg, minimum 6 axles, maximum axle weight 16,500kg | 5 working days to highway and bridge authorities; dimensions may need to be given to the police |
| Special order | More than 150,000kg or 16,500kg per axle, more than 6.1 metres wide, or more than 30 metres rigid length when loaded | 5 working days to highway and bridge authorities and 2 working days to police, with the special order carried in the vehicle |
Each category also carries its own plating and speed limits, which are set out in the guide. Special orders are issued on behalf of the Secretary of State by National Highways from its Birmingham office, and the guide states the authorisation must be carried in the vehicle.
Why the category matters to you as the customer
- It sets the lead time. The jump from 2 working days to 5 working days is the difference between moving this week and moving next.
- It sets the trailer. Axle counts and maximum axle weights decide what the load can travel on, which decides the deck height and therefore the bridges you can pass under.
- It sets the speed. Higher categories run at lower speed limits, so the journey takes longer and may need overnight parking.
- It changes who else is involved. Above the STGO limits you are into special order territory, with its own application and its own programme.
Verify the category and the thresholds for your specific movement with your haulier and against the current gov.uk guide before relying on them. Figures on this page were taken from the gov.uk special types enforcement guide and the National Highways abnormal loads pages and checked in August 2026, and government guidance is revised from time to time.