Metrolink launches North America’s first zero-emission hydrogen-powered ZEMU on San Bernardino’s Arrow line
Metrolink launched North America’s first zero-emission hydrogen-powered passenger train, the ZEMU, on the Arrow line in San Bernardino on September 13, 2025, offering clean daily service between downtown San Bernardino and the University of Redlands.
- First-in-continent ZEMU: Zero-Emission Multiple Unit (ZEMU) entered passenger service after extensive FRA-focused testing.
- Route and service: Runs the nine-mile Arrow corridor linking downtown San Bernardino and the University of Redlands and connecting to Metrolink’s San Bernardino Line.
- Manufacturer and cost: Built by Stadler (Switzerland) at roughly $23 million per train; first of three units for Arrow.
- Environmental and regulatory milestone: Hybrid hydrogen fuel-cell and battery design produces only water vapor and meets FRA requirements after ~10 months of testing.
What ZEMU is and how it works
The Zero-Emission Multiple Unit (ZEMU) is a hybrid train that combines hydrogen fuel cells with on-board batteries to power electric traction motors. Hydrogen reacts in fuel cells to generate electricity while batteries capture energy for acceleration and regenerative braking, making the only operational tailpipe emission water vapor. Details and local reporting are available from GovTech and the SBCTA press release.
Design and safety considerations
SBCTA and Metrolink state the hybrid architecture was chosen to meet both local service patterns and the Federal Railroad Administration (FRA) safety and performance rules. The vehicle arrived in San Bernardino in June 2024 and underwent roughly 10 months of testing on Metrolink tracks to validate signaling, grade crossing integration, and platform compatibility (SBCTA, GovTech).
Route, ridership and service pattern
ZEMU operates on the nine-mile Arrow corridor, a five-station line that links downtown San Bernardino with the University of Redlands. The line originally opened with diesel trains in 2022; ZEMU now serves the same corridor and connects riders to Metrolink’s San Bernardino Line for travel toward Los Angeles Union Station. SBCTA invited the public to ride free on the inaugural day, September 13, 2025 (SBCTA, VVNG).
Cost, procurement and funding
Each ZEMU unit cost roughly $23 million and was built by Swiss manufacturer Stadler. Federal funding was a key component of advancing the project; local officials including Rep. Pete Aguilar and SBCTA Board President Rick Denison highlighted the investment’s value for commuting and air quality goals. The first ZEMU arrived in June 2024 and was tested for about ten months before entering passenger service (GovTech, SBCTA).
Regulatory milestone and testing
The ZEMU is being described as the first self-powered, zero-emission passenger train in North America that meets FRA requirements. Reaching that milestone required extensive testing on Metrolink infrastructure to ensure compatibility with existing signaling, grade crossings, and station platforms. SBCTA reports testing lasted about ten months and included safety checks, operational trials, and compatibility evaluations (SBCTA, VVNG).
“This project shows how zero‑emission rail technology can be safely integrated into existing commuter networks,” said local officials noting the importance for air quality and commuting.
Local visibility, design and implications for the Inland Empire
The ZEMU features a blue-and-white water-vapor wrap, two passenger cars with a center power pack housing hydrogen tanks and batteries, visible across Arrow stations. Beyond cleaner rides, the project signals new regional investment: jobs for testing, operations and potential fueling/maintenance capacity. Officials position the ZEMU as a model for other agencies — but long-term climate benefits will depend on how hydrogen is produced and how fueling infrastructure scales (GovTech, SBCTA).
Economic, political and social effects
Economic: The $23 million per-unit investment and federal grants have supported local contracts, testing, and could create long-term O&M jobs if fueling and maintenance are built regionally.
Political: The launch has been framed as a bipartisan success combining federal support and local leadership.
Social: Cleaner, quieter trains can reduce diesel pollution near stations, and free inaugural rides raised public awareness about the new service (VVNG).
Questions investigators are tracking
- Fueling infrastructure: Where will hydrogen be produced, stored and dispensed as the fleet expands? SBCTA has outlined plans but wider regional networks remain a challenge (SBCTA).
- Operating costs: How maintenance and fuel costs compare to diesel over the long run, especially if hydrogen prices fluctuate.
- Scaling: Can zero‑emission trains be adopted on longer or heavier commuter corridors while meeting FRA rules and budget constraints?
- Equity and access: Will service and outreach improve transit access across the Inland Empire for commuters, students, and workers?
Practical applications for residents
Riders can now board a zero-emission ZEMU on the Arrow line and connect to broader Metrolink service for commutes into Los Angeles and across the region. SBCTA plans a three-train fleet for the corridor as part of a phased diesel-to-zero-emission transition (SBCTA).
Reporting and sources
This article draws on reporting and releases from the San Bernardino County Transportation Authority and trade and local outlets:
All original facts, figures and source URLs are preserved above as cited links.
