Trial of road exhaust technology slashes DMU’s diesel emissions

A trial of exhaust technology has cut diesel emissions on a South Western Railway Class 159 diesel multiple unit by more than 80%.

In partnership with rolling stock leasing company Porterbrook and emissions company Eminox, SWR fitted a new exhaust to the ‘159’ for a six-month trial, based at Salisbury depot. The result: nitrous oxides reduced by 80% and both carbon monoxide and particulates reduced by more than 90%.

Although not new technology, the proven system transfers from road vehicles to the railway for the first time.

“It’s at a point where the emissions are now very close to modern engines,” said SWR Engineering Director Neil Drury.

“The potential is that these old engines can be similar to older cars. As city centres start to clamp down on car diesel emissions, we can expect the same for trains. It means the older trains become more relevant, extending their operating life.”

One three-car Class 159 unit was fitted for the Eminox trial, funded by the Department for Transport’s first-of-a-kind scheme. A second trial is now under way.

The exhaust uses an oxidation catalyst and a filter to remove ultra-fine particles that are known to be carcinogenic and which are associated with respiratory health conditions.

Although rail is perceived as the most sustainable form of mass public transport, diesel engines still power a third of all rolling stock and the engines on many DMUs are of a design developed more than 30 years ago. Road vehicles from the same period have long since been consigned to the scrap heap, producing noise and emissions that are considered unacceptable today.

The ‘159’ has run on the London Waterloo-Exeter St Davids route, where electrification is not planned in the foreseeable future and where the fleet could potentially continue to operate for another decade.

Eminox Sales Director Carlos Vicente said: “For more than 20 years we have developed cuttingedge retrofit technology, which has significantly reduced diesel exhaust emissions from public transport and commercial vehicles. We have worked in partnership with SWR and Porterbrook to adapt our technology for the rail sector.”