Zero-Emission Multiple Unit (ZEMU)

North America’s first federally compliant self-powered, zero-emission passenger train arrived in San Bernardino County on June 20. The train’s arrival at the San Bernardino Depot Train Station marks a significant milestone on its incredible journey from concept to reality. The passenger train, a Zero Emission Multiple Unit (ZEMU), uses a hybrid hydrogen and battery technology to propel the train and power onboard electrical systems. Water vapor is the only emission generated from the propulsion system, making this a clean transit alternative.

The new ZEMU is easy to spot with its signature blue and white water-vapor design wrapped around the train’s two passenger cars and center power pack where the hydrogen and battery propulsion system is located. In the coming weeks, ZEMU will begin the final phase of testing that will include trips on the Arrow line and Metrolink system checks with a goal of safe entry into service later this year.


SBCTA is leading the charge for a greener passenger rail future by piloting zero-emission rail technology for the new Arrow service between San Bernardino and Redlands.

A contract signing in 2019 between Stadler US and SBCTA cleared the path to begin the manufacturing of the first two-car hydrogen-powered passenger train to operate in the United States. Providing a hydrogen-powered rail vehicle to passengers is a critical milestone demonstrating SBCTA’s investment in the county’s sustainable future, zero-emission transportation options and the transition away from using fossil fuels to protect the health of its 2.1 million residents and visitors.

To support the operations of the ZEMU vehicle, specific upgrades and modifications are required to the existing Arrow Maintenance Facility to facilitate hydrogen storage, refueling and required safety enhancements. Construction of the storage and fueling facility is expected to begin in 2024.

ZEMU will offer passengers the most environmentally rail friendly vehicle in the United States and deliver a balanced and sustainable transportation system for San Bernardino County’s future.

Project Webinar
SBCTA hosted a webinar on Wednesday, February 7, 2024 to provide information about the Zero-Emission Multiple Unit and Arrow Maintenance Facility.
To watch the webinar, click the image below.

Fact Sheets

Arrow Maintenance Facility Hydrogen Fuel Upgrade Project – Draft Environmental Impact Report Documents

Arrow Maintenance Facility Hydrogen Fuel Upgrade Project – Final Environmental Impact Report

Project Reports

Planning Documents

Press Releases

SBCTA is committed to being a part of the solution to reduce greenhouse gas emissions and improve air quality.

As we all learn about the urgent need to combat climate change, most importantly by reducing the largest contributor – fossil fuels. ZEMU has proven to be a viable and more environmentally friendly alternative to traditional transportation methods.

Air Quality Benefits

  • When hydrogen is used in a fuel cell to produce electricity, the only byproduct is water vapor, making it a clean alternative to traditional diesel-powered trains. This significantly reduces the carbon footprint of the transportation system and helps combat air pollution.
  • Hydrogen fuel cell trains like ZEMU provide clean air, meaning it will not emit harmful pollutants such as nitrogen oxides and particulate matter, which are common emissions from diesel engines, or greenhouse gases such as carbon dioxide.
  • Communities along the train route will experience improved air quality, leading to better respiratory health for residents and a cleaner living environment.

Reduced Noise Pollution

  • Hydrogen trains tend to be quieter than traditional diesel trains, which can be especially beneficial for communities located near the train route.

Increased Energy Efficiency

  • Hydrogen as a rail fuel supports zero carbon goals as a clean energy source and offers a more powerful and efficient energy output than fossil fuels.
  • Compared to internal combustion engines in diesel trains, hydrogen fuel cells can convert a higher percentage of the energy content in hydrogen into usable power for propulsion. This efficiency can result in reduced energy consumption and reduced operational costs for the train system.


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