Know your limits: Tractor and trailer speeds

If you’re driving your tractor at speeds greater than 20mph (32km/h) on the road, you’re probably breaking the law.

Although many tractors are fitted with gear boxes that allow speeds of 32mph (50km/h), this doesn’t mean to say you may drive them at this speed on public roads.

“The law differs between the UK and the continent,” explains NFU road transport adviser Peter Garbutt.

“In this country it’s not legal to travel at speeds greater than 32km/h for most tractors, even if they are fitted with a 50km/h box.”

Exceptions are specialist high-speed tractors such as JCB Fastracs and Unimogs.

“The key design difference is that a conventional tractor has a fixed, rather than a suspended back axle. There are also differences in brakes, tyres and other areas.”

If towing a trailer speed must be kept below 20mph, even when driving a Fastrac, unless the trailer, including its brakes, is of a commercial spec.

“You need dual-line, fail-safe braking and a minimum braking efficiency of 45%,” says Mr Garbutt.

Vehicle Limit (mph) Notes
Most tractors. 20 The limit for agricultural motor vehicles is 40mph, but they must meet design specifications as set out in the Road Traffic Regulation Act, the Construction and Use (C&U) regulations. Requirements include sprung back axle, specialist brakes and tyres. See NFU Business Guide on high-speed agricultural vehicles for more. There are derogations provided the vehicle is kept below certain speeds, with 20mph being the general limit.
Fasttracs, Unimogs, some other tractors 40 Notify police or get annual dispensation order. Speed limit 20mph.
Tractor and trailer 20 In most cases
40 Only if BOTH tractor and trailer have approved commercial spec. For the trailer this includes dual-line, fail-safe braking. There are also width and length restrictions
4×4 and trailer 50-70 Depends on the road and how your vehicle is classed.
DfT information sheet on agricultural tractors. Brief guide from the Department for Transport that gives an overview of the legal requirements when taking tractors on the road, with links through to further information.
Agricultural vehicles – An examiners guide NFU Business Guide on agricultural vehicle dimensions. Detailed guide to the legal requirements for tractors and trailers provided by VOSA. The layout is good and easy to follow. VOSA also has a helpline to answer specific queries from road users – 0300 123 9000.
NFU Business Guide on high-speed agricultural vehicles> Detailed guide to legislative requirements (available to NFU members only).
Do you know your limits? NFU briefing giving guidance on speed limits for 4×4 and other large, van-type venhicles (available to NFU members only).


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