Another Continuum

In my head – and I suspect in most people’s heads – there is a sharp distinction between subways and similar mass transit and other heavy rail. Light rail, particularly street cars running on a shared right-of-way seem like a third different thing. But in reality, the differences get very blurry the longer you look. Boston’s Green Line, for example, is about half subway and half street car.

One of the blurry differences concerns branches. On long-distance railroads (including commuter rail) where trains on any branch are spaced half an hour or more apart, having a bunch of switches to shunt trains onto the right branch is not a problem. On a busy mass-transit subway, where trains might have headway of only a few minutes during rush hour, every switch movement is a potential delay. This might seem obvious now, but older el and subway systems were designed more like railroads. Here’s Max Hubacher’s 1951 photo of the somewhat insane rail layout at Broadway Junction in East New York, Brooklyn.

That junction had been built much earlier to allow els on the Canarsie, Broadway, and Fulton lines to swap ends – you could mix and match the main line to the west with the tail end to the east. The construction of the Fulton subway – the A train – simplified that mess, and the eventual abandonment of the idea of swapping, so that the Broadway el always went to Jamaica (now the J train) and the 14th Street subway always went to Canarsie (now the L train), simplified it more.

There are still a lot of these tangles, many of them the result of someone in the 1910s or 20s thinking of the subway system like a railroad. They can be simplified by eliminating trains crossing from one track to another in ordinary service, even if the switches remain for maintenance use. And all of this has been a lead up to a really interesting article on planned untangling: “MTA plans to fix Brooklyn’s worst subway bottlenecks, IDs 70 congested spots in system“.