Currently a third tunnel is being built and apparently it's "the largest construction project in New York history". The project was begun in 1970 and won't finish until 2020. It cost 6 billion. When the third tunnel comes online, it will allow for the other two tunnels to be shut down for repairs for the first time in their history. Scenes from Die Hard were filmed in Tunnel 3.
This is big, long-term stuff folks. Makes me feel kind of proud of civilization.