High-speed trains have always been a tough sell in the U.S. The technology is as old as Sputnik, but Congress and the states chose to keep the focus on interstate highways in the late 20th century. American critics still complain that bullet trains are too expensive, too underutilized and potentially unsafe.

But that hasn't stopped the high-speed dreaming. A plan for a train to whisk passengers from Dallas to Houston in 90 minutes is moving ahead; officials announced in early January that they will conduct an environmental...