7 June 1996

Speeding questions…

Unusual, but it is possible for a tractor driver to be done for speeding. Michael Bird starts this special feature with a look at tractors on the road

SPEED merchants beware – driving your tractor flat out on the public highway can endanger yourself, other road users and land you in serious trouble with the law.

The cloud of uncertainty surrounding the legal speed of farm vehicles on the road is due to one basic reason: There are no design speed limitations included within the definition of an agricultural motor vehicle, a legal classification which embraces tractors, combine harvesters, self-propelled sprayers and forage harvesters, among others.

An agricultural motor vehicle (AMV) is defined simply as "a motor vehicle which is constructed or adapted for use off roads for the purpose of agriculture, horticulture or forestry and which is primarily used for one or more of those purposes". There is no mention whatsoever of speed in the definition.

But UK legislation does have speed-based construction and use conditions which will apply to any AMV driven on the road. The end result is that not all AMVs capable of exceeding 20mph can legally do so when on the public highway.

Awareness needed

The NFUs transport specialist, Steve Smith, points out that farm users need to be aware of the speed-related requirements before using any agricultural motor vehicle on the public road, in particular those capable of exceeding 20mph.

"Although there is no statutory definition of a high speed agricultural vehicle, the term is generally used to describe those capable of on-road speeds in excess of 20mph," he explains. "Such vehicles have to meet higher standards of construction than those driven at speeds of 20mph or less.

"The problem is that a number of manufacturers produce farm machines which have design speeds in excess of 20mph but do not meet all of the higher construction standards legally required for use on the road."

To help users, Steve Smith has compiled a guide which highlights those areas where the standards of high speed vehicle construction and use are higher or different from those driven at less than 20mph.

First, all of the following points must be satisfied before a tractor or other AMV can be driven along a public road at more than 20mph.

Braking specification and performance – in general, standards are the same as those for HGVs, to include dual circuit braking systems and a minimum efficiency of 50% (25% up to 20mph). Vehicle owners and users must ensure the brakes are maintained to the same standard as originally manufactured and supplied from new.

Suspension – all-wheel sprung suspension is required. It is not sufficient to have suspension on the front axle only.

Tyres – must have no cuts more than 25mm (1in) long or across 10% of the tyres section width (whichever is the longer) deep enough to reach the ply or cord. The tyre must also be free from lumps, bulges or tears and have no ply or cord showing.

Further, pneumatic tyres must be fitted with a minimum 1mm tread depth and with the base of any groove in the original tread pattern clearly visible in a continuous band over three-quarters of the treads breadth around the outside of the tyre. The tyres must also have been designed and made to support the vehicles maximum permitted axle weights when driven at its maximum design speed.

Safety glass – is required for the front window and for those to either side of the driver in any high speed AMV first used on or after 1 June 1986.

Speedometer – a mandatory fitting.

Horn – also mandatory.

Mudguards – all wheels must be protected by wings or similar covers to catch water, mud or spray.

Windscreen washers – mandatory on all high speed AMVs first used after 1 June 1986.

Mirrors – again, if first used on or after 1 June 1986, both an internal and external offside mirror are required. If no clear view can be obtained from the internal mirror, then a nearside external mirror must be fitted.

Engine noise limits – limit varies according to date of manufacture, construction standards and speed of use. But operators must ensure an appropriate exhaust silencing system is fitted and maintained in good condition at all times.

Engine emission standards – a complex area with different standards at different design speeds. But any AMV designed for high speed use should meet the required standards when purchased new.

Having satisfied the above construction and use standards, there are a number of lighting and marking requirements which must be met by AMVs capable of speeds in excess of 25mph and weighing more than 7.5t.

Testing and plating

Other points which Steve Smith says require regular clarification include annual testing and plating (all agricultural motor vehicles are currently exempt), vehicle licensing (there is no special criteria for high speed agricultural vehicles), and driver licensing and age (same rules apply as for all agricultural motor vehicles).

If the high speed vehicle meets all of the specific construction and use requirements speeds of up to 40mph can be used on all public roads where lower speed restrictions do not apply. But it is important to ensure that towed trailers or machines satisfy the additional high speed hauling requirements.

A number of these such as tyre load and speed ratings and the fitting of wings and lights are similar to those of the towing vehicle. But there are variations in brake requirements according to the year of manufacture.

Interestingly, while AMVs are not normally permitted on motorways, properly constructed high speed AMVs may do so if they meet four conditions: They must be a wheeled vehicle, fitted with pneumatic tyres and capable of at least 25mph "on the level". They must also be licensed in an excise duty class other than the concessionary agricultural machine rate. If they meet all these criteria trailers can also be hauled.

&#8226 Copies of the NFUs guide to High Speed Agricultural Vehicles (Ref: 125) is available to members only via the NFU Orderline (0345-585324).

Many tractors are capable of exceeding 20mph on the public highway, but not all meet the design criteria to legally do so. Hence, beware.

JCBs Fastrac – one of the few properly constructed high speed agricultural motor vehicles legally permitted to travel at speeds of more than 20mph on the UKs public highways. Permitted top speed is 40mph.