The design of this inflatable object was commissioned by the US Department of Homeland Security to be used in response to terrorist attacks against subways. But perhaps it could also be used to prevent future subway floods like those that happened recently in New York City:
The plugs can be inflated in about three minutes. But once inflated, they are pressurized with either air or water.
The existing test plug is roughly 32 feet by 16 feet and holds 35,000 gallons of water.
The manufacturer, Dave Cadogan, speculated about their utility in New York City:
If New York had had plugs, "I think they could have stopped a fair amount of incursion of water in the transit system," he said.
Team members say the plugs are cheaper than the leading alternative -- floodgates. The prototype plug cost about $400,000, and costs could go down if the plugs are manufactured in quantities.