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Freight Rail’s Bridge to a Net-Zero Future: Wabtec’s Evolution Series Tier 4 Locomotive

May 13, 2024

Nearly a decade into its emissions-crushing run, Wabtec’s Tier 4 innovation platform is just getting started.


In the early 2000s, Wabtec (then GE Transportation) faced an important decision. With Tier 2 emissions standards for CO2, oxides of nitrogen (NOx), and particulate matter (PM) set to take effect in 2005, should the company modify its popular FDL locomotive to meet the stricter environmental regime – the kind of incremental approach adopted by its competitors – or adopt a different strategy altogether?

Trains of Thought │ Wabtec Corporation

Sensing that sustainability was here to stay and that emissions standards would continue to rachet down in the future, Wabtec did what it has historically done at key moments of industry change: it bet on innovation.

Instead of making a short-term upgrade to its legacy FDL locomotive, it invested in the future, developing a new engine platform built for both performance and sustainability. The Evolution Series Locomotive was born.

For nearly 20 years now, the Evolution Series platform has been a fundamental part of Wabtec’s portfolio and its customers’ fleets. It has answered the call of freight railroad’s immediate challenges, while providing a rich base for continuous improvement, breakthrough innovation, and step-change advances that have guided the railroad industry to this day – all while complying with ever more restrictive emissions requirements.

Now it faces its biggest challenge yet: leading the industry on its journey to a net-zero future. And the star of the show is the Evolution Series Tier 4 locomotive.

While others ‘zigged,’ Wabtec ‘zagged’

When the EPA signed Tier 4 emissions standards into law, it set an incredibly high bar. By 2015, railroads would have to reduce PM and NOx emissions in new engines by 90% versus older locomotive models. While the seven-year (2008-2015) phase-in period provided locomotive manufacturers some cushion, the exacting new standards left nowhere to hide.

Trains of Thought │ Wabtec Corporation
Wabtec's innovative Tier 4 Engine uses exhaust gas recirculation (EGR) technology instead of aftertreatment technology.

A 90% reduction would require a radical approach. The majority of manufacturers flocked to urea-based “aftertreatment” technologies as the solution, one which required additional equipment in the engine block and brought with it both a hit to fuel performance and an expensive maintenance program.

Wabtec zagged. It incorporated exhaust gas recirculation (EGR) technology instead of aftertreatment technology, avoiding the need for cumbersome, expensive, and performance-draining emissions systems altogether.

Class 1 railroads voted with their feet. More than 1,000 Wabtec Tier 4 locomotives are in operation today. These 432,000-pound, six-axle giants deliver 4,500 horsepower and can reach a maximum speed of 75 mph pulling thousands of tons of freight. And the combination of strong fuel and operational performance, along with achieving the major 90% reduction in PM and NOx emissions, has made the Wabtec Tier 4 engine a popular choice across applications, from marine to locomotive and high- to low-horsepower environments.

“The success of our Tier 4 engine is really a function of a solid technology development plan and a very committed team to drive its implementation to the required level of efficiency and reliability,” says Rogerio Mendonca, Wabtec’s President, Freight Equipment. “We’ve got 10,000+ Evolution Series engines running around the world today, of which more than 1,100 are Tier 4. It is important to remember that these platforms are built on decades of proven performance, which is what our customers are really looking for from us.”

The sustainable future

Trains of Thought │ Wabtec Corporation
Wabtec launched the Evolution Series Tier 4 locomotive in 2015.

Yet EGR and other technological advantages resident in Wabtec’s early Tier 4 engines, and the strong market adoption that followed, only tell half the story. The Tier 4’s ultimate success, and the reason it is factoring prominently in the sustainability ambitions of Class 1 railroads, is that it is a proven platform for ongoing innovation.

Since its introduction in 2015, Wabtec has invested heavily in its Tier 4’s performance and adaptability to new, more environmentally friendly fuel sources. On the performance front, Wabtec has continued to improve the Tier 4’s reliability while teasing out additional fuel efficiency. In fact, Wabtec is testing new fuel-saving solutions similar to its FDL Advantage product to reduce fuel consumption and emissions.

Yet it’s Wabtec’s leadership in exploring and investing in the use of alternative, low- and no-emissions fuels for its Tier 4s – a platform with nearly 20 years of proven innovation, reliability, and efficiency already built in – that positions these versatile engines as the bridge technology to reaching the rail industry’s net-zero emissions goals. Wabtec Tier 4 engines are already hard at work accommodating a significant number of decarbonization and sustainability technologies, while the transition to pure zero-emissions technologies mature and evolve.

For example, today’s Wabtec Tier 4 engines can run on biodiesel and renewable diesel fuels, as well as liquified natural gas. These lower-carbon options provide railroad carriers maximum flexibility to pursue the decarbonization path that is right for them, an approach that helps them meet current regulations – and near-term sustainability pledges – while preparing for a zero-carbon future.

The options and innovations don’t stop there. In fact, they are only just beginning as Wabtec prepares its Tier 4 engine to burn hydrogen. And while this next chapter in the pursuit of zero-emissions solutions will take time to play out and achieve commercial viability, the Tier 4 will be there when it does – just as it is here now delivering customers a reliable ‘near-zero’ path as long as is needed.

“Today we use our Tier 4s in all parts of our system and in all types of service,” reflects Keith Solomons, Vice President of Mechanical at BNSF Railway. “When we made the decision to go with buying new Tier 4s from Wabtec, it was strategic because we knew that by buying new, we’d be buying the cleanest operating, most fuel efficient and most reliable locomotive available rather than remanufacturing existing older vintage locomotives.”

A bridge to the future

One of the beauties of Wabtec’s Evolution Series Tier 4 locomotive is that it is ultimately ‘fuel agnostic.’ It accomplishes the hard task of radically reducing emissions while continuing to deliver on reliability, efficiency, and total cost of ownership. And it does all this while also providing the flexibility to accommodate the next major sustainability innovation, whatever it is and whenever it happens, where it matters most – on the tracks.

“Our job at Wabtec is to have one foot in the present to help customers meet today’s challenges, and one foot in the future to ensure they will be able to capitalize on tomorrow’s opportunities,” concludes Mendonca. “Our Evolution Series Tier 4 Locomotive is the bridge technology that reliably spans our customers’ and industry’s evolving sustainability needs.”

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