Harvard professor Edward Glaeser keeps dumping cold water on the dreams of anyone hoping for high speed rail.

In the fourth installment of a series looking at the economics of high speed trains at the Economix blog, Glaeser argues "rail’s potential reshaping of the American economy" is overblown.

Supporters of high speed trains, point to evidence of fast trains transforming slow towns. Glaeser cites Ciudad Real a town outside of Madrid in Spain, that's been lifted by high speed trains.

Well, the United States is not Spain, Glaeser says. High speed trains will not save dying towns like Buffalo, Detroit and Cleveland.

Here, Glaeser presents his least convincing work in the series. It seems obvious that Buffalo, which would still be a 2.5 hour train ride to New York City, wouldn't be transformed by high speed rail.

What about somewhere closer, like Philadelphia? Glaeser says it's still not happening:

Philadelphia is the more natural beneficiary of high-speed rail access to Manhattan; there are already people who live in Philadelphia and commute to New York. Yet even in this most propitious setting, the coming of Acela seems to have had little impact on the population decline of Philadelphia or growth of Wilmington. Perhaps the absence of any trend break in population growth around 2000 just reflects the incremental nature of the Acela investment, but there is little here to bring confidence that rail lines revitalize cities.

We've looked closely at the Philadelphia to New York Acela. It's a joke. The trip takes about an hour and a half, and costs between $90 at the low end, to $280 at the high end for a round trip ticket. There's no discounted monthly passes either. The bus will shuttle you between the cities in 2 hours, and a roundtrip ticket costs $20.

The prohibitive cost of the Acela makes it impossible for rationalizing a move to Philadelphia and commuting to New York on economic grounds.

If a truly high speed rail line were set up between the two cities, and the commute only took 45 minutes to 1 hour, and the tickets were more reasonably priced, $1,000-$1,200 a month, we think Philadelphia really becomes the sixth borough of New York, as the New York Times called it in 2005 (to the consternation of Philadelphians).

Let's say we are right, and Philly gets a little boom from the high speed rail, does it even matter? Not according to Glaeser, who says "I don’t see why is it in the national interest to disperse economic activity from Manhattan to Buffalo or Philadelphia. I have long argued that the economic case for directing economic aid to declining regions is weak."