Like a mirage speeding across the dusty desert outside Pueblo, Colorado, the first hydrogen-fuel-cell passenger train in the United States is getting warmed up on its test track. Made by the Swiss manufacturer Stadler and known as the FLIRT (for “Fast Light Intercity and Regional Train”), it will soon be shipped to Southern California, where it is slated to carry riders on San Bernardino County’s Arrow commuter rail service before the end of the year. In the insular world of railroading, this hydrogen-powered train is a Rorschach test. To some, it represents the future of rail transportation. To others, it looks like a big, shiny distraction.