Many UK farms have trailer brakes that fall below the minimum legal requirement for road use, according to research. Although there are proposals to update regulations, farmers and contractors must ensure limits and trailer spec are met.
“The vast majority of trailers only just provide the minimum 25% braking efficiency required when trailers are used up to speed of 20mph – and that is not guaranteed even with new trailers,” says braking specialist Andrew Scarlett, who has carried out research on UK farm trailer braking standards.
For their part trailer manufacturers point out that, though they have offered higher-spec brakes for some time, farmers tend to buy the cheaper-spec versions.
Dr Scarlett also says that farmers are becoming much more aware of trailer braking issues and more interested in complying with the regulations. Despite that, maintenance of trailers is still almost non-existent, he points out.
There are proposals to establish a new category of high-speed tractor and trailer that could travel at 50kph with a gross train weight of 31t (compared with the current 24.4t limit).
This would allow an 8t tractor to haul a 23t trailer (17t pay load + 6t unladen weight). It would involve higher braking and suspension requirements and, more controversially, annual roadworthiness assessments carried out by dealers.
The scheme would not be compulsory – those who are content to travel at 20mph at 24t gross train weight could carry on as they do at the moment.
“This will demonstrate to the public and the road transport lobby that agricultural vehicle operators are responsible road users,” says Dr Scarlett. “This scheme, if adopted, has the potential to move agricultural transport out of the 1980s and bring it up to today’s requirements.”
Discussions between industry and the Department for Transport on this issue continue.
How the law stands
UK road traffic laws divide farm tractors and trailers into two categories.
If you travel at less than 20mph (32kph) your trailer can perfectly legally use single-line hydraulic brakes. But if you go above that figure it should have two-line pneumatic brakes with a failsafe system, high-speed axles, springs and the correct lights.
If the trailer was made after 1 May 2002, it should technically have ABS brakes, too.
In practice, there are plenty of hydraulically-braked tractors running around on the roads at 25mph (40kph), which means that their drivers and owners are technically (though almost certainly inadvertently) breaking the law.
The same applies to what’s called the gross train weight. This is the combined weight of the tractor, the trailer and the contents of the trailer. The legal maximum for farm tractors and trailers is 24,390kg.
If you’re sitting on a 150hp tractor (typical weight 6t) hauling a trailer (typical unladen weight 4t) filled with 14t of wheat, your train weight is 24,000kg, happily just below the legal limit.
But put a 200hp tractor (typical weight 8t) on the front of a bigger trailer (typical unladen weight 6t) with 18t of corn on board and your total train weight is now 32,000kg. Common enough, but technically illegal.
See our FAQ on trailer brakes.
Take the Academy on trailer brake safety.
DfT information sheet on agricultural tractors. Up-to-date brief guide from the Department for Transport that gives an overview of the legal requirements with links through to further information.
DfT information sheet on agricultural trailers. A similar guide for trailers, again with links through for more information.
NFU Business Guide on agricultural trailer brakes. Useful guidance and interpretation of the legislation (available to NFU members only)
NFU Business Guide on agricultural trailers and trailed appliances. Outline summary of what you can tow on the road (available to NFU members only)
NFU Business Guide on agricultural vehicle weight restrictions. Brief summary of weight restrictions and braking requirements (available to NFU members only)
NFU Business Guide on high-speed agricultural vehicles. Detailed guide to legislative requirements (available to NFU members only)