RAILWAY AGE, NOVEMBER 2025 ISSUE: Just this past September, something historic happened in the high desert of Southern California: The first hybrid hydrogen fuel cell (HFC) battery-electric passenger train in the U.S. began carrying passengers.
On Sept. 13, the San Bernardino County Transportation Authority (SBCTA) Zero Emission Multiple Unit, nicknamed ZEMU, began operating on a nine-mile stretch between San Bernardino and Redlands. ZEMU, which uses a hybrid hydrogen and battery technology for propulsion and emits only water vapor, is the culmination of a multi-year effort to bring such trains to California. The technology underwent testing in Switzerland following a showing at InnoTrans in 2022, and then a four-car trainset headed to the Transportation Technology Center in Pueblo, Colo., for further testing. SBCTA began testing it on the area’s network in the summer of 2024.
Switzerland-headquartered Stadler Rail developed the technology. Stadler Project Manager Kaden Killpack tells Railway Age that “Stadler’s first hydrogen vehicle is performing well in San Bernardino, and we are grateful for our partners and customers who were heavily involved in introducing this technology to the U.S. passenger rail market.”
While Stadler’s HFC trainset, the FLIRT H2, may be the first of its kind in the U.S., it’s not likely that it will be the last. In February 2024, state agency Caltrans ordered six more, with the first of these expected to enter revenue service in 2027 on other intercity and regional rail lines. Caltrans’ $127 million contract with Stadler is part of a $10 billion, multi-year effort to bolster zero-emission vehicle use and infrastructure in the state. The total number of HFC trainsets is 10; all are expected to be in service by 2028.
“The U.S. seems to be the most interested market in HFC rail vehicles currently,” Killpack says. “Countries where few rail routes are equipped with OCS (overhead catenary system) electrification, like the U.S., are most suitable to deploy this kind of technology.”
HFC Train Plans
Just when more HFC passenger trains will run on U.S. networks remains unclear, as the technology is not a priority of the POTUS 47 Administration. The White House recently pulled funding to develop hydrogen hubs in western U.S. states, including California. Port of Los Angeles Executive Director Gene Seroka confirmed in the port’s monthly media briefing that California lost its federal funding to develop the hub.
But even though a timeline for passenger trains using hydrogen in the U.S. is unclear for now, the technology is being refined in Europe and could be transferable to the U.S. one day. “We have a proven technology in Europe that could potentially address North America’s needs,” French rail developer Alstom tells Railway Age. Interest in zero-emission solutions, including hydrogen and battery-based, has grown across North America in the past five years, particularly for greenfield commuter or regional lines, according to the company.
Indeed, compared to diesel trains, Alstom says its hydrogen trains allow for a reduction of up to 700 tons of CO2 per train per year, and emit less noise compared to diesel, while their performance, such as their acceleration and speed, is comparable.
“The transport sector represents nearly 25% of world-wide emissions from fuel combustion. It is inevitable: Many countries have set targets to phase out diesel, particularly in Europe and India, to meet climate goals,” Alstom says. For instance, around 10,000 diesel trains will need to be replaced in Europe by 2035, representing around 80% of the worldwide fleet. Because of this, Europe is a potential market for hydrogen trains.
Alstom already has HFC trains operating in Europe. In Germany in 2022, its Coradia iLint™ trainsets started passenger service, marking the first time worldwide that hydrogen trains were being used for passenger rail. The company has delivered 41 Coradia iLint™ hydrogen trainsets to two German rail agencies: 27 to RMV in the state of Hesse and 14 to LNVG in the state of Lower Saxony.
“As a pioneer of this new technology, Alstom has faced some challenges in terms of operational stability,” the company says. “To enable stable and smooth passenger service, we’ve been working on a new generation of fuel cell technology, which will be gradually implemented beginning later this year.”
Italy and France are other countries set to use Alstom’s HFC trainsets: FNM (Ferrovie Nord Milano) in Italy’s northern region of Lombardy and FSE (Ferrovie del Sud Est) in southern Italy ordered 16. In France, national railway company SNCF ordered 12 Coradia Polyvalent™ dual-power units on behalf of four French regions in 2021. These trainsets combine catenary-electric and HFC traction equipment. The Italian trainsets received support from the European Union’s IPCEI Hy2Tech program; the first is expected to be operational for passengers in the coming months. The French trainsets, originally built at Alstom’s Reichshoffen site in France, are now being assembled by CAF France.
“In general, Europe has the infrastructure to support hydrogen trains. So far, however, the number of refueling stations specifically designed for them corresponds to the comparatively small number of hydrogen train projects. Only an increasing demand will ensure a growing supply,” Alstom says. In North America, Alstom collaborated with Chemin de fer Charlevoix and Harnois Energy to offer passenger service using HFC trains between Quebec City and Baie Saint Paul in the summer of 2023.
Killpack says that while ZEMU, also known as the FLIRT H2 in the U.S., is the only hydrogen-powered Stadler train in operation, the company has a demonstration train, the RS ZEO, currently in commissioning and testing in Germany. Stadler also has customers in Italy who have ordered hydrogen trains, although they are not yet in passenger service. The U.S. ZEMU “will enable us to study performance,” Killpack says. “As with any new vehicle type, we will continuously improve its design and performance with new vehicle orders. Stadler’s upcoming vehicles will continue to prioritize resiliency, reliability and redundancy to ensure great performance.”
Meanwhile, another company, Germany-based Siemens Mobility, has produced the Mireo Plus H, a hydrogen train model that has been deployed in Germany.
Finding Opportunities
Although HFC passenger trainsets are in operation, there are several challenges hindering widespread adoption. Alstom sees challenges in two areas. For starters, “the cost of hydrogen has continued to increase in many markets across the U.S. and Canada, making the cost of power significantly higher than it would be with either diesel or electrified systems,” the company says. “Also, the infrastructure requirements to implement a hydrogen or battery solution remain daunting for many agencies, particularly in cases where the agency operates on a host railroad. Both challenges would need to be meaningfully addressed to see greater uptake of zero emissions technologies.”
“The cost of electrification has gone up,” notes Killpack. “In the U.S., we’ve seen costs as high as $15-$17 million per track-mile, just for the OCS, traction power and signal upgrades. For smaller routes or routes with low-density or low-frequency service, the hydrogen vehicle option is far more economical.”
Nonetheless, Alstom, Stadler and Siemens still see plenty of opportunities to further progress in hydrogen trains in passenger and freight applications.
Alstom says it has designed the Traxx Shunter H™, which it describes as “an innovative new-build switcher solution.” It has received funding from the French government’s France Relance, France 2030 and the European Union’s NextGenerationEU, as part of the IPCEI Hy2Tech program. Alstom adds it has been working with German partners on re-tractioning of a diesel switcher locomotive to hydrogen. A retrofitted Alstom unit was converted from diesel to hydrogen drive, powered by hydrogen direct combustion, and began operations in September in Salzgitter, Germany. “With this research project, we are once again pioneering the use of hydrogen in rail transport,” says Alstom Vice President of Services, Central and Northern Europe François Muller. “We are expanding the vehicle modernization spectrum with a doubly sustainable approach. Thanks to this solution, our customers can switch to emission-free operation without having to replace their existing fleet.”
Alstom is upbeat about a future with more hydrogen trains. “As the industry gains a deeper understanding of the entire ecosystem for each solution, including the technology and the infrastructure, operations, maintenance and repair, resource experience, training and availability and other external factors, the whole value chain will be optimized for better performance and reliability,” the company says. “This will help to close the maturity gap between hydrogen fuel cell/battery propulsion and traditional propulsion over time.”
