North America’s first federally compliant zero-emission passenger train

Moving toward increased connectivity and zero emissions passenger rail in California

The San Bernardino County Transportation Authority (SBCTA) sought to expand its public transit network in southern California and reduce greenhouse gas emissions by replacing the diesel vehicles with zero emissions multiple units (ZEMUs) as a follow-on project to the Redlands Passenger Rail project.

Development and implementation of a hydrogen train

On behalf of the SBCTA, we prepared a grant application that won $30 million initially and $15.8 million subsequently from the California Transit and Intercity Rail Capital Program. The funds were allocated for research, development, and implementation of a ZEMU vehicle along with the supporting infrastructure.

We then evaluated zero emissions technologies including alternative fuels, batteries, hydrogen fuel cells, and hybrids. In July 2019, the SBCTA’s board unanimously approved the implementation of a hydrogen fuel cell and battery hybrid vehicle.

Our team then supported the SBCTA by overseeing pilot vehicle design, manufacturing, testing, commissioning, and regulatory approval with the Federal Railroad Administration.

Designing hydrogen fueling and maintenance facilities with safety at the forefront

The Mott MacDonald team led the design, procurement, and permitting of the supporting infrastructure, including upgrades to the Arrow Maintenance Facility (AMF) and installation of hydrogen fueling infrastructure.

The ZEMU vehicles will be maintained in the existing AMF building, which is currently used for diesel vehicle maintenance. We led the evaluation of the AMF building conditions to identify necessary modifications to meet hydrogen code requirements and install hydrogen fueling infrastructure. Working closely with members of the Hydrogen Safety Panel, the team completed a code analysis to determine how to retrofit the facility to address hydrogen specific hazards. We also completed computational fluid dynamic modeling to support the application of the codes and define additional classification zones within the facility. The team also led the design for a temporary fueling facility and worked with local authorities to obtain the permits to operate.

An industry first in North America

The ZEMU vehicle is now open for service as of September 2025, marking a major milestone. It stands as the first federally compliant hydrogen fuel cell-battery hybrid passenger train operating in North America. Testing and commissioning is complete, and the vehicle is actively demonstrating its capabilities. The train holds the Guinness World Record for the longest continuous journey by a hydrogen fuel cell passenger train without refueling – traveling 1,741.8 miles in a single run.

The ZEMU fueling and maintenance facilities are also the first of their kind in North America. This zero emissions train improves air quality and showcases the potential for greenhouse gas reductions and other environmental benefits across California and the United States. Thirteen additional ZEMU vehicles purchased by the California Department of Transportation (Caltrans) will deploy statewide in 2027.