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Road Users

Braking laws for agricultural vehicles

Braking laws for agricultural vehicles, including maximum design speeds and maintenance of trailer braking systems.

This content is for general information only. It does not, and is not intended to, provide legal or technical advice or to represent a legal interpretation of the matters it addresses.


Frequently asked questions

The following brakes are required on all tractors:

 Maximum design speed is 40 km/hDesign speed of tractor is over 40 km/h
Service brakeminimum brake efficiency of 25%minimum brake efficiency of 45%
Parking brakeminimum brake efficiency of 16%minimum brake efficiency of 16%
Emergency brakenot required 

The 40 km/h speed threshold has been chosen to improve road safety. This revised standard is less demanding than other proposed braking standards contained in EC Regulation (EU) No. 167/2013.

If an ISO7638 electrical connector has been fitted to the rear of a tractor and the tractor is drawing a trailer equipped with ABS the connector must be used. However, if the tractor is not fitted with the ISO connector and the tractor is being used to draw an ABS-equipped trailer, a means of powering the ABS system must be provided. This can be done using the trailer’s brake light circuit.

You should consult the original manufacturer or one of their authorised distributors. You should never attempt to carry out repairs yourself on a braking system that you have not been trained in. A fully-loaded trailer can account for up to 75% of the tractor-trailer combination’s kinetic energy i.e. the energy or force generated by the moving combination – so it is of vital importance that agricultural trailers are equipped with adequate braking systems for their intended operating speed. They should also be properly maintained to ensure that they work effectively as part of the tractor-trailer combination.