For years mass transit experts have worked to find an ability to block off sections of the tunnel system to stem flooding. While retrofitting existing tunnels with watertight doors seemed the obvious answer the price has been prohibitive.

Now they think they’ve found the answer. And it’s as simple as an inflatable plug. A giant blow up capsule that when inflated will fit snugly into the subway space sealing it off until the danger of flooding has passed.

In January 2012 the Department of Homeland Security (DHS) Science and Technology Directorate (S&T) successfully tested an unprecedented technology for containing flooding or dangerous gases in mass transit tunnels: a giant plug. S&T’s Resilient Tunnel Project (RTP) has developed an enormous inflatable cylinder, tunnel-shaped with rounded capsule-like ends, that can be filled with water or air in minutes to seal off a section of tunnel before flooding gets out of control.

The plug is made of space suite material and is strong and resistant to tears. Its quick inflation gives the ability to tunnel systems to repair and return to normal with minimal damage.

Watch the video below to see how this new technology will work. It is expected to be available in two years.