The Obama administration, failing to learn the lessons of nearly 40 years of subsidizing Amtrak, is embarking on a huge high speed rail project that promises to spend tens of billions of dollars for meager benefits.

As Robert Samuelson points out in his Washington Post column, we have been subsidizing about 78,000 Amtrak users to the tune of about $50 per ride. The results? A negligible decrease in traffic congestion, and greenhouse gas emissions.

Ah! But high speed rail will be different says Obama/Biden:

The White House promises fabulous benefits. High-speed rail "will loosen the congestion suffocating our highways and skyways," says Vice President Biden. A high-speed rail system would eliminate carbon dioxide emissions "equal to removing 1 million cars from our roads," adds the president. Relieve congestion. Fight global warming. Reduce oil imports. The vision is seductive. The audience is willing. Many Americans love trains and regard other countries' systems (say, Spain's rapid trains between Madrid and Barcelona, running at about 150 mph) as evidence of U.S. technological inferiority.

There's only one catch: The vision is a mirage. The costs of high-speed rail would be huge, and the public benefits meager.

President Obama's network may never be built. It's doubtful private investors will advance the money, and once government officials acknowledge the full costs, they'll retreat. In a recent report, the Government Accountability Office cited a range of construction costs, from $22 million a mile to $132 million a mile. Harvard economist Edward Glaeser figures $50 million a mile might be a plausible average. A 250-mile system would cost $12.5 billion and 10 systems, $125 billion.

That would be only the beginning. Ticket prices would surely be subsidized; otherwise, no one would ride the trains. Would all the subsidies be justified by public benefits -- less congestion, fewer highway accidents, lower greenhouse gases?