Corridors connecting populous regions with large job centers, rail transit networks, and existing air travel markets scored best in the report by America 2050, a national urban planning advocacy group.

The study also recommends that the federal government adopt a more systematic approach to evaluating future investment in high-speed rail.

"America 2050 strongly believes that investments in high-speed rail will be essential to the long-term economic success and mobility of the nation and its megaregions," Robert Yaro, president of Regional Plan Association and co-chair of America 2050, said in a statement. "The report recommends, however, that the federal government adopt a data-driven, ridership-based approach to choosing rail corridors for federal investment in the future in order to direct funding toward projects with the greatest market demand."

The study, "High-Speed Rail in America," cites ridership potential as the top factor in determining if a corridor is suitable for investment, identifies the specific conditions that generate ridership demand, and scores each corridor according to strength in those areas.

Top-performing corridors determined to have the greatest potential demand for high-speed-rail ridership include New York-Washington, Chicago-Milwaukee, Los Angeles-San Diego, Tampa (via Orlando) to Miami, Dallas-Houston, Atlanta-Birmingham, Portland-Seattle, and Denver-Pueblo.

Scoring was based on factors that have contributed to rail ridership in other systems around the world: regional and city population size and density, employment concentrations, rail transit accessibility, air travel markets, and the composition of job markets by sector.

Based on the analysis, the report proposes that the federal government adopt a similar approach to evaluating and prioritizing future investments based on the greatest potential ridership demand. It also calls for a new nationwide study of long-distance travel in America, the majority of which takes place by automobile. The last nationwide study of this kind was completed in 1995 and is outdated, according to America 2050.

The report acknowledges that while ridership is an important factor in selecting potential rail investments, it is not the only consideration. American 2050 contends the federal government must also weigh factors such as project readiness, ability to acquire rights of way, and local political support for rail projects.

The report is a follow-up study to America 2050's 2009 report, "Where High-Speed Rail Works Best," which analyzed 27,000 potential corridors or "city pairs" and ranked them according to a weighted average of the six survey criteria, but did not consider the alignment of the corridors or the cities between each pairing. This new report refines the 2009 analysis by accounting for the network benefits of having multiple stations along a corridor.

A key advantage of rail over air is that it can make intermediate stops and pick up additional passengers without expending the time or fuel that would be required of airplanes to make stops.

"Now that the initial rush of high-speed rail stimulus grants have been awarded to regions such as California, Florida, and the Midwest, it's time to build the foundation for a program that will have long-term sustainability and gain public support," said Petra Todorovich, director of America 2050. Collecting data on long-distance travel and identifying the most promising markets for high-speed rail is essential to ensuring our money is well spent."

The 56-page report, an executive summary, interactive maps, and more information are available at bit.ly/Am2050HSR. AASHTO's high-speed-rail information center is available at www.highspeed-rail.org.