Who has heard of the "hydrail"?

[Tom Macrery]

This is a citation from the "Word Spy" web site.

hydrail n. A railway system that uses hydrogen fuel cell technology; a train powered by hydrogen fuel cells.
Example Citations:
Hydrogen trains, or hydrail, are not subject to many of the barriers preventing the mass adoption of fuel cell transportation, and their deployment could provide a transportation infrastructure around which additional hydrogen and fuel cell applications may be built. The first hydrogen-powered train models are currently being demonstrated in Japan and Europe.
—"Appalachian State University co-hosts International Hydrail Conference in Spain," US States News, April 14, 2008
And then there are trains, or "hydrails," as some call them.
"Hydrogen fuel cells as an application for passenger trains is very real," says Mike Hardt, vice-president of North American services for Bombardier.
In fact, Ontario may have some catching up to do if it's serious about being a world leader in hydrails. A European consortium called The Hydrogen Train concluded a study last year that looked at what it would take to demonstrate a hydrogen train in Denmark by 2010.
—Tyler Hamilton, "All aboard the GO hydrogen express," The Toronto Star, October 21, 2007
Earliest Citation:
Charlotte this spring will host what organizers call the world's first conference on rail technology powered by hydrogen fuel cells.
The First International Hydrail Conference will be held May 6 at the Renaissance Charlotte Suites Hotel. Its seven sponsors include the Charlotte and Mooresville chambers of commerce, Centralina Council of Governments and the Environmental Protection Agency.
Speakers will include a researcher from Japan's Railway Technical Research Institute, which will soon demonstrate the first hydrail equipment.
—"Charlotte to host hydrogen technology conference," Charlotte Observer, February 26, 2005

[John Ashworth]

Hydrogen trains, or hydrail, are not subject to many of the barriers preventing the mass adoption of fuel cell transportation

What are these barriers and why aren't trains subject to them?

Presumably the mass and bulk of hydrogen cells are two factors where a train has an advantage over a car or aircraft?