Well, you got the name wrong -- it's the Armstrong Tunnel -- but you did notice it was narrow. That puts you one up on some of the region's top law-enforcement officers, at least. For years they never questioned the story of a Housing Authority officer, John Charmo, who in 1995 claimed he shot black motorist Jerry Jackson to death when Jackson pulled a 180-degree turn inside the tunnel's narrow confines and rushed him. It took years, and a civil suit filed by Jackson's family, for police to reopen the case and discover what you have already noticed.
The tunnel was opened in 1927 named after Joseph Armstrong, who served variously as a City Councilor, the mayor of Pittsburgh, and an Allegheny County Commissioner. You can see his name on the plaque mounted at the tunnel's two entrances -- one where the 10th Street Bridge intersects Second Avenue, the other at Forbes Avenue near the old Fisher Scientific building. Perhaps the oddest thing about the tunnel, though, is that like the Jerry Jackson investigation, the whole construct is bent -- about 45 degrees near the Forbes Avenue end.
There's an old urban legend that this bend reflects a flawed design that was only corrected when the tunnel was almost finished -- and that the person responsible for the screw-up killed himself in despair. I've found no evidence to support that, and both the tunnel's architect, Stanley Roush, and its chief engineer, Vernon Cowell, worked on later projects. (On the other hand, we are talking county government here: It's possible they died but remained on the payroll.) My own guess is that the tunnel curves at the end simply to form a better angle with Forbes -- if the tunnel led straight from the bridge on the other side, the intersection at Forbes would be awkward, even by Pittsburgh standards. Other theories have it that old mine shafts or disputes over property rights may be to blame. Given that it was built by the contracting firm of Booth & Flinn -- a major beneficiary of political graft and corruption in earlier decades -- maybe it was just designed not to disturb anyplace the bodies were buried.
As to why the tunnel was built, did I mention that Joseph Armstrong lived in the South Side? While there had been bridges at 10th Street since the 1860s, the tunnel made it easier for Armstrong's neighbors to get into and out of town.
Of course, today's rough-and-ready SUVs -- and the suburban off-road cowboys who drive them -- might be able to ascend the sheer face of the Bluff. At least, that's what I gather judging from the TV commercials. But bear in mind that the tunnel was built for an earlier era.
In fact, there did used to be direct access to the top of the Bluff: Bruce Cridlebaugh, whose Web site www.pghbridges.com is a reliable and useful source of bridge and tunnel information, notes that the Fort Pitt Incline used to connect Second Avenue with the place where Duquesne stands today. Like most of the city's other inclines, however, the Fort Pitt was torn down around the turn of the century. A stairway remains, but not even an SUV could negotiate it -- no matter what the Housing Authority police may say.