Huge inflatable plugs -- now being developed by the federal government to protect subway tunnels from terrorist attacks -- likely could have saved some of New York's subway tunnels from storm-related flooding, according to plug developers, some of whom are wistful that development wasn't completed in time for Hurricane Sandy.

The Department of Homeland Security successfully tested a plug in January, using the 16-foot diameter prototype to hold back pressurized water at a test tunnel in Morgantown, West Virginia. Another test to demonstrate the plug's reliability is scheduled for next week.

But project managers said only one current-generation plug has been manufactured, and they say they are two years away from marketing them to the nation's transit and highway authorities.

"If we would have had these things installed in the right places (in New York), they could have made a terrific difference," said Greg Holter of the Pacific Northwest National Laboratory. "The problem is we don't have a stock of things that we could put in place. It's not like we have a bunch of these sitting in a warehouse," Holter said. "It's a little frustrating really that we weren't at a better stage at this thing."