Everybody hates els. They’re ugly and noisy and cities will even move their train station away from downtown to tear them down. The hypocritical treatment of els versus much wider and noisier elevated highways is fortunately the subject of another post, on Market Urbanism. I would instead like to discuss how elevated rail could be made to work in cities, allowing the construction of rapid transit at acceptable cost.
One way viaduct structures can be made more acceptable is if they’re branded as a new technology. This is the case of Vancouver’s SkyTrain, the JFK AirTrain, the Honolulu light rail line, and monorails. Another is if they’re along rights-of-way that are already considered blighted, such as freeways; this also helps explain why the JFK AirTrain was built whereas the proposed subway extension to LaGuardia was not.
As a first filter, the above examples suggest that the most useful elevated rapid transit – grade-separated mainline rail, or els over major streets – is impractical due to community opposition. But as a second filter, we could simulate some features of both cases in which viaducts are more acceptable – new technology and freeway right-of-way. If we build a well-designed and aesthetic arched viaduct over a wide road, this could pass community muster. For example, Robert Cruickshank prominently used the second and further photos in this CAHSR Blog post to argue that grade separations on the Peninsula will not be a blight. The 7 viaduct in Sunnyside is also a good example of an el.
As a third filter, the success of the elevated train over Queens Boulevard comes precisely from the enormous street width. East of Sunnyside, Queens Boulevard becomes practically a highway, nicknamed the Boulevard of Death and excoriated on Streetsblog for its lack of pedestrian scale. At the same time, the 7 above Roosevelt Avenue darkens the street and the steel el structure is very noisy. But when there is an el about Queens Boulevard, everything works out: the street is broken into two narrower halves, with the el acting as a street wall and helping produce human scale; the el is also farther from the buildings and uses an arched concrete structure, both of which mitigate its impact.
It’s possible to mitigate even further and imitate the methods of the AirTrain or SkyTrain. Those use modern viaduct construction techniques and are therefore relatively unobtrusive: see for example this photo on Greater City: Providence, in the context of reinstating some of the elevated infrastructure torn down in the 1980s. Even if the technology is your standard railroad, newer viaducts can reduce impact. In addition, the old els were built with very tight curves, producing squeal; building with wider curve radii is the norm today, and although it increases visual impact and can require more takings, it reduces noise impact, often to practically zero.
Commenters from various Northeastern suburbs have told stories of how people don’t even notice the electric regional trains, but complain about the freight trains. Of course those regional lines were built in the 19th century, but they were built to mainline standards, rather than to the standards of the Chicago L, and thus have what by rapid transit standards are wide curves.
The 7 el is 12 meters wide, and works fine on Queens Boulevard, which is 60 meters from building to building, and poorly on Roosevelt, which is 22. These give an upper and lower bound for street width. The N/W el on Astoria, at 12 meters over a 30-meter street, is also quite bad, though perhaps not as much as the 7 el on Roosevelt. The 1 el in Manhattanville is an imposing steel structure, but its problem is one of topography and height rather than street width, and so it should be put in the category of good els from the perspective of width; this is 12 meters over a 43-meter street. Finally, the Metro-North viaduct in Harlem is 18 meters over a 43-meter street; the area is quite blighted, though it could be a characteristic of the neighborhood more than of the el. Optimistically, it seems that a more modern two-track el, about 9 meters wide (and thus blocking light less than the New York examples regardless of street width), could work over a 30-meter street, such as the Manhattan avenues.
Of course, another issue is the surrounding density. Despite the above calculation I would not want to see new elevated lines on the Manhattan avenues. Partly this is because the population density in Manhattan is so high that the higher cost of a subway is acceptable. But partly it’s because the buildings are tall and would not pair off with the viaduct nicely as they do in Sunnyside. However, it could be a good solution in Queens and the North Bronx, where, additionally, the streets that could take rapid transit are wider than a standard Manhattan avenue.