High-speed rail. For supporters, the words conjure visions of trains hurtling across the country at more than 200 miles per hour, bypassing congested highways and long airport security lines alike.

The Obama administration in 2009 sought to take the first steps toward realizing this vision, identifying 10 corridors for potential high-speed rail projects and providing seed funds to get the projects rolling. However, facing opposition in Congress and in several states, the plans were dramatically scaled back; only two projects—in...