Swiss manufacturer Stadler and Sardinia's ARST have introduced hydrogen trains to lines that were too small and too winding for overhead electrification. The engineering is quietly revolutionary.
Most conversations about hydrogen trains focus on the headline-grabbing mainline projects: Germany's Coradia iLint, which entered regular service in 2022, or the UK's HydroFLEX prototype. These are standard-gauge trains designed for standard-gauge railways. What Stadler and ARST have just done in Sardinia is different, and arguably more important.
They have built the world's first hydrogen-powered narrow-gauge trains.
Why narrow gauge matters
Narrow-gauge railways — tracks narrower than the standard 1,435 mm — are everywhere in the world, but almost nowhere in the conversation about rail decarbonisation. They crisscross Sardinia, Corsica, Sri Lanka, parts of India's northeast and hill stations, Japan's rural prefectures, and dozens of other regions where terrain made standard gauge impractical or unaffordable.
These lines share a common problem: they are too lightly used to justify the cost of overhead wire electrification, but too important to their communities to simply shut down. Many still run diesel trains from the 1970s and 1980s, and face mounting pressure to decarbonise. Battery-electric is an option for short routes, but narrow-gauge lines are often long, winding, and hilly — exactly the conditions where batteries struggle with range and weight.
Hydrogen solves this neatly. A fuel cell converts hydrogen to electricity on board, with water vapour as the only emission. The range of Stadler's new trains is approximately 800 km on a single fill — enough to run an entire day's service on most narrow-gauge networks without refuelling.
The Sardinia trains
The contract, worth approximately 200 million euros, covers 25 trains for ARST, the regional transport operator in Sardinia. Each train can reach 100 km/h — not fast by mainline standards, but entirely appropriate for the tight curves and gradients of Sardinia's 950 mm gauge network.
Stadler, the Swiss manufacturer behind the Tyne and Wear Metro's new fleet and dozens of other European rail orders, engineered the trains from scratch rather than adapting a standard-gauge design. The hydrogen storage, fuel cell, and traction systems had to be packaged within the tighter dimensional constraints of a narrow-gauge vehicle, which is a substantially harder engineering problem than putting the same technology in a larger train.
The first trains have been unveiled and are entering the testing and commissioning phase. Revenue service is expected to begin later in 2026.
What this means for India
India still operates several narrow-gauge and metre-gauge lines, including the famous Darjeeling Himalayan Railway (610 mm gauge, a UNESCO World Heritage site), the Kalka-Shimla line (762 mm), and the Matheran Hill Railway (610 mm). These lines are cultural and tourism assets, but they run diesel locomotives that are increasingly difficult to maintain and source parts for.
Indian Railways has electrified 99.6% of its broad-gauge network, but the hill railways and narrow-gauge branches are in a different category entirely — stringing overhead wires through the Himalayan hairpin bends above Darjeeling is neither practical nor desirable. Hydrogen could offer a path to zero-emission operation while preserving the character of these historic lines.
Sardinia's trains won't make headlines the way a 450 km/h speed record does. But for the hundreds of narrow-gauge railways around the world that quietly keep communities connected, this may be the most consequential rail innovation of the year.