Since the creation in the late 1990s of a working group dedicated to the issue of reducing railway noise caused by freight traffic, UIC has played a key role in the work to replace cast iron brake blocks with composite material.

On 22 February 2018 the group held its 100th meeting, which highlights the importance of the subject and the work conducted over the last 20 years.

The first meeting of B126.13 was held on 6 and 7 January 1999, following a decision taken by SC5T (the sub-committee SC5T) in June 1998.

With regard to the longevity of the service life of railway material, the objective of this working group was twofold:

• Development of a brake block with high friction level to be used on newly-built rolling stock in place of the formerly used cast iron brake block (the so-called “K” block)
• Development of a brake block with a coefficient of friction similar to cast iron allowing the replacement of cast iron brake blocks on existing freight wagons

The coefficient of friction of cast iron is not constant but depends on both application force as well as speed. As it was more difficult to develop a brake block with these requirements than a brake block with a constant coefficient of friction, the work in the beginning was dedicated to the development of a “K”-block allowing the design of “quiet” new wagons. This first phase of the project ended in 2003 with the system approval of K blocks. From 2004 onwards, new wagons were equipped with composite brake blocks.

To achieve an audible reduction of the rolling noise emitted by wagons a minimum of 75% of the wagons in a train have to be equipped with composite brake blocks. With the slow renewal rate of the freight wagon fleet (useful lifetime of freight wagon is between 30 – 35 years) noise reduction would only become evident after 15 – 20 years.

This is why after the system approval of the K block the WG (different working groups) continued their efforts on the development for the so-called “LL” blocks with the goal to find a solution to replace cast iron blocks in existing wagons without any other need for change.

To bear in mind the complexity of the task, a few requirements need to be met:

• Identical braking performance under all operational circumstances (dry, wet, snowfall, long inclines)
• Thermal protection of wheel in case of brake failure
• No negative influence on running behaviour (equivalent conicity)
• Faultless function on track circuits
• LCC not higher than cast iron with regard to the difficult economic situation of freight transportation on rail

Finally, in 2014 after numerous tests on dynamometers and on tracks on long alpine inclines as well as under arctic or extreme conditions, the system approval of LL blocks was achieved allowing the 1:1 replacement of cast iron brake blocks in existing rolling stock.

However, the work of the WG is not yet over. A number of persistent problems (exchangeability of K-blocks, braking behaviour in winter from low initial speeds in shunting yards, clear definition of threshold between S- and SS-brake) are still awaiting a solution.

Since its creation the WG has published 42 technical reports and documents and five new editions of Leaflets.