The Obama administration recently pledged $8 billion for high-speed rail. While just a fraction of the overall stimulus package and just a drop-in-the-bucket of what is needed to build a real national high-speed rail network, the funds generated considerable hub-bub and outright jubilation among regionalists, environmentalists, energy efficiency advocates, and those who have long fought for improved U.S. rail transit. It also has encouraged a mad political scramble for funds as regions position for federal monies. In Canada, there is a mounting drumbeat for high-speed rail connecting Windsor, Toronto, Ottawa, Montreal, and Quebec cities and also for connecting Vancouver to Seattle.

For starters, here's a map of proposed U.S. high speed rail projects:





It's clear that the U.S. and North America lag far behind countries like Japan with its Shinkansen or France with the TGV on high-speed rail connectivity.



But how to base decisions on what routes get funded? How to avoid a purely political outcome and create a framework for investing in high-speed rail that makes the most economic sense?

There are many metrics - from population concentration to economic activity - which can be used to gauge the merits of high-speed rail routes. But my own research on mega-regions provides a potentially useful framework for thinking about where and how to invest in a national high-speed rail system.





Mega-regions are large-scale economic units of multiple large cities and their surrounding suburbs. My research team and I defined them using satellite images of the world at night to identify contiguous economic areas with more than five million people producing $100 billion or more in economic output. The world's 40 largest mega-regions account for two-thirds of all the global economic activity and 85 percent of the world's technological innovation while housing just 18 percent of its people.





Here's a map of North America's mega-regions.

The largest of North America's mega-regions is the great "Bos-Wash" mega-region initially identified by the geographer Jean Gottman. It stretches down the east coast corridor encompassing the east coast cities of Boston, New York, Philadelphia, Baltimore, and Washington, D.C., and is home to more than 50 million people and produces more than $2.2 trillion in economic activity. Its economic output is greater than that of the UK and France and more than double that of India or Canada. The second biggest, which Gottman dubbed "Chi-Pitts," covers more than 100,000 square miles and is home to 46 million people, producing $1.6 trillion in economic output. Taken together, America's mega-regions produce more than three-quarters of its economic output and the lion's share of its innovations (see the table below).



