2001: Dr. Michael Swain with the University of Miami at Coral Gables attempted to simulate two car fires, one created by a 1/16th inch puncture in a gasoline fuel line, the other by a leaking hydrogen connector. He video taped the experiment to document what would happen if the leaks ignited. As the photos below clearly demonstrate, consumer fears about hydrogen as a transportation fuel would seem to be pretty much unfounded.
While the gasoline-fed fire eventually consumed the second test vehicle, leaving it a smoldering heap of charred steel and melted glass, the hydrogen fire was over in less than two minutes and left the hydrogen-tank equipped test car virtually undamaged. In fact, the heat inside the car never got above 67 degrees.
Dr. Swain points out in Fuel Leak Simulation that while the gasoline fire started as the result of a simple, small hole in the fuel line, for the hydrogen fire to occur, it would have taken the catastrophic failure of four separate safety systems, all at the same time, a highly unlikely occurrence.
Dr. Michael Swain Hydrogen Leak Study (PDF)