Colas Rail UK, part of global infrastructure group Bouygues, ran two separate evaluations of Sulnox Eco™ across distinct rail applications, covering:

• Four tampers, rail-mounted machines packing ballast under tracks, across a a nine-month period

• Class 66 and 37 locomotives, used on the Rail Head Treatment works, across a three-month period.

Testing was facilitated by A&S International, with emissions independently measured by SOCOTEC and Cura Terrae (formerly Atesta).

The locomotives alone showed a:

Alongside significant reductions in particulate matter (PM) with a 32.6% reduction in PM2.5 and 30.4% reduction in PM10.

Following the successful evaluations, Colas Rail UK plans to roll out Sulnox Eco across its full diesel locomotive and tamper fleet. The company is also encouraging key supply chain partners—such as rail vehicle hire providers—to adopt the solution, supporting broader Scope 3 emissions reductions across the industry.

With a verified 4.5% improvement in fuel efficiency, full adoption is expected to deliver six-figure annual fuel savings. Combined with substantial emissions cuts and improved engine performance, the evaluations confirm that Sulnox Eco offers a strong operational and environmental return.