Pittsburgh has three twin-bore vehicular tunnels. Two of these are now being rehabilitated, and the third was recently refurbished. Each carries its name on its portals. I began thinking about those names when I saw the newly rebuilt portals of what Pittsburghers generally refer to as the Liberty Tubes. Over the twin bores on both the north and south side of Mt. Washington are the words, incised in large capital letters, “LIBERTY TUNNELS.” (Liberty Tunnels has always been the official name of the bores.)
What is curious is that the names of the other tunnels are the “Fort Pitt Tunnel” and “Squirrel Hill Tunnel.” Worldwide, paired tunnels are generally given singular names. Why is “Liberty Tunnels” (or “Liberty Tubes”) plural? I have no idea.