High Output machines

Our machines make upgrade work safer and quicker

Network Rail has invested £300m in High Output in the last 12 years – helping to make our High Output fleet the third largest in the world. We maintain and operate our High Output fleet – maintenance is not outsourced.

Why High Output is so important

Ballast cleaning

Over time, ballast wears down and becomes rounded. The pieces of ballast then fit together less easily, reducing the ballast’s effectiveness.

Fine pieces of granite, like sand, are also created by attrition – these are known as ‘fines’. These fines stick together when combined with water in the ballast, making the ballast like a lump of concrete. This hinders track drainage and the flexibility of the ballast to constrain the track as it moves under traffic.

Ballast cleaning removes this worn ballast, screens it and replaces the ‘dirty’ worn ballast with new angular ballast.

With our modern ballast cleaner systems (BCS) there’s a significant reduction in the need for railway workers to be on the track while the work takes place – most operations are controlled from inside the cabs, so this limits exposure to the dangers of diesel fumes, ballast dust and passing trains.

On the newest BCS – the only one that can ballast clean third-rail track – even the wagons are fully automated.

At half-a-mile long, our BCS trains include: locomotives each end (to move the train to and from the work site in traffic up to 60mph); power cars to propel the train while in operation; 22 empty wagons for ballast waste; the ballast cleaner; the tamper/dynamic track stabiliser (DTS) machines (scroll to the end of this page to read more about DTS machines), and 22 wagons full of new ballast. This is a more environmentally friendly alternative to previous ballast cleaners.

How it works

The BCS inserts ballast into the track immediately behind the excavating cutter bar, bringing forward new ballast from its full wagons.

A tamper/DTS, integrated into the machine, improves the track geometry as the whole system progresses along the track, making use of track geometry management systems to install the track position to a high level of precision. The integrated DTS consolidates the track for extra stability.

Any poor quality ballast (spoil) excavated from the track is rejected and fed forwards by conveyors to empty wagons, all contained on the same track.

Because there is no need for wagons on the track alongside the machine, the line adjacent to the BCS can remain open for passenger and freight trains, minimising disruption. The removed spoil is taken back to a High Output Operations Base and then on to specialist facilities to be further processed and recycled as roadstone.

Another advantage of our BCS is that there’s no need to cut rail and remove it for the ballast cleaning process to take place, so our engineers don’t need to dismantle the track and it’s safer. It’s also quicker, and the track can reopen at a line speed of 80mph or more because the rail doesn’t need to be welded (necessary when the rail is cut).