New EC proposals regarding minimum braking efficiency for trailers could require trailer manufacturers to incorporate some big improvements in the braking department.

While tractors have become ever more sophisticated, more powerful, faster and larger, the basic design of trailers has remained much as it was many years ago.

And when it comes to brakes, despite travelling at faster speeds with more weight on board, they are still only required to offer a minimum of 25% braking efficiency.

All of which is not satisfactory, says research engineer Andy Scarlett, whose latest project is aimed at raising user awareness of the inadequate performance of many agricultural trailer braking systems, and, he adds, provide guidance regarding the practical means and economic viability of putting things right.

Speaking at an IAgrE Agricultural Transport Conference in Peterborough last week, Dr Scarlett said the proposed EC braking requirements were likely to exceed, by some considerable amount, the braking ability of most trailers, both old and new.

The EC Directive proposals and the Transport Research Laboratory recommendations are that:

  • Trailers need to have 50% braking efficiency rather than the current 25%.
  • There should be no design speed categories – everything with brakes must achieve a minimum 50% braking efficiency.
  • Failsafe braking system that are activated when the trailer accidentally parts company with tractor.
  • Trailer parking brake to be applied from the tractor seat.
  • Trailed equipment over 3500kg total axle load will require same braking system as trailer.
  • Trailer and trailed equipment braking systems will require Type Approval testing before they can be sold.

Such proposed improvements in trailer braking efficiency will be welcomed by tractor makers, who have had to cope with an abundance of brake warranty claims caused, they insist, by inadequately-braked trailers relying on the towing tractor’s brakes to stop or slow down.

The new proposals also set out minimum braking efficiencies for tractors, though most modern tractors already comply with them.

Should these proposals be accepted it is likely they will become a national requirement for new tractors and trailers by about 2010, which means that new trailers are going to have to be fitted with braking systems which meet the 50% efficiency requirement.

Many agricultural trailers are fitted with braking systems designed to operate within the 20mph (32kph) UK speed limit for vehicles without suspension.

But the vast majority of tractors are now capable of 25mph (40kph) and more than a few can manage 30mph (50kph), and the demands on the braking system multiply dramatically at such speeds. Increasing speed from 20mph to 30mph, for example, increases the energy dissipation requirement by over 140%.