With the federal high-speed rail program on life support, a study released by a Cambridge think tank yesterday makes the case for long-term investment in bullet trains - and for targeting the money to the Northeast and California, instead of sprinkling it throughout the country.

The “megaregions’’ between Boston and Washington, D.C., and San Francisco and Los Angeles most closely mirror in population and distance the global corridors where trains already move millions of riders a day at speeds approaching or exceeding 200 miles an hour, including Paris-Lyon in France, Tokyo-Nagoya-Osaka in Japan, and Barcelona-Madrid in Spain, according to the report.

Arriving at a fraught moment for transportation funding, the “High-Speed Rail: International Lessons for US Policy Makers’’ report from Cambridge’s Lincoln Institute of Land Policy and New York-area partners argues for the economic and land-use benefits of high-speed lines in the two regions, where distance and density best position bullet trains as alternatives to driving and flying.

“We see high-speed rail as a transformative investment . . . [but] we are not advocating that we should build high-speed trains between every city in America,’’ said Petra Todorovich, lead author and director of America 2050, a collaboration between the Lincoln Institute and New York’s Regional Plan Association to help the country better prepare for the 100 million additional residents projected in about 40 years.

The limitations of the nation’s rail network were underscored yesterday when the scheduled three-hour, 10-minute Amtrak Acela Express train carrying Todorovich to Boston arrived a half-hour late, dropping her at South Station just moments before the scheduled forum nearby.

The Acela trains, the closest thing the country has to high-speed rail, are capable of traveling 150 miles an hour but average less than half that, because of congestion and frequent curves; they also run late nearly 20 percent of the time.

An Amtrak proposal unveiled last year would shorten travel times from Boston to New York to two hours and New York to Washington to 90 minutes - but costs an estimated $117 billion over 30 years for design, permitting, land acquisition, and construction.

That may be a small fraction of the money invested in highways over the past half-century, but it dwarfs the initial $10 billion spent by the federal government on high-speed rail in the past two years - a broad banner under which money was spread throughout the country and invested in improving conventional rail as well as creating high-speed lines.

Though the White House wants to spend $8 billion more next year, the House budget eliminated the spending, while the Senate has sought $100 million. And since the expiration in 2009 of the last surface transportation bill - which determines federal priorities for funding highway, rail, and transit projects - Congress has failed to agree on a new bill, though it recently passed its eighth short-term extension.

The Lincoln report does not ignore those considerable political and budgetary problems but takes an advocate’s optimistic long view. It offers strategies culled from European and Asian successes for financing, constructing, and operating high-speed rail lines - centralized government and dedicated taxes help - and suggests a more targeted approach than has been tried in the United States.

“We see this as a generational investment, and minor setbacks from year to year are completely to be expected,’’ Todorovich said. “The interstate highway system did not get started until a dozen years after it was proposed.’’

Armando Carbonell, a Lincoln Institute senior fellow and former executive director of the Cape Cod Commission, a regional land-use agency, likened the promise of high-speed rail to that of broadband Internet in the age of dial-up modems.

“Looking back, would anybody choose to stay in that world?’’ he said.

Eric Moskowitz can be reached at emoskowitz@globe.com.

© Copyright 2011 Globe Newspaper Company.