Under the Chicago El. Photo by the author.
Elevated rail has a bad name; urban rapid transit requires full grade separation. These two facts are inconveniently opposed to one another. Is there a future for elevated rail in urban and suburban areas? Cheaper elevated construction opens the door for more rapid transit expansion in our regions, but only if the real negatives of elevated structures can be overcome.
Some background reading:
- Grade separation is the critical element for rapid transit. Jarrett Walker highlights the technical reasons and advantages to full grade separation: speed, frequency, and reliability.
- Richard Layman presumes urban elevated rail isn’t workable in this post title, asking us to remember why we build transit underground. He notes that the real value for transit is in the grade separation.
- Jarrett Walker again writes about the tensions and interaction between good transit (speed, frequency, reliability), good urbanism and urban design (streetscapes, aesthetics, design), and the demand for cost-effective infrastructure, using Honolulu’s planned rapid transit project as an example.
- Yonah Freemark looks at the same case of Honolulu here – construction is currently stalled as legal battles play out.
- Discussion at archBoston on how we’ve done better with integrating elevated structures into the cityscape in the past; a similar survey from the CA HSR blog.
- Alon Levy on conditions to make elevated rail work: branding it as something new to avoid the visual associations with Chicago-like structures; ensuring that new structures are aesthetically pleasing; and focusing on wide rights-of-way with room to build without overshadowing the street.
- Keep Houston Houston on the “limits of cute transportation.”
In addition to mitigating the negatives from elevated structures, there’s also the matter of emphasizing the positives of transit. Considering that a great deal of the public opposition to elevated structures is likely now framed by thinking of freeway overpasses and flyovers rather than Chicago-style Els, it’s worth considering the relative capacities of each. Market Urbanism writes about benefits vs costs, citing Robert Fogelson’s Downtown:
Elevated rail lines are far smaller in footprint than elevated highways, and although highways may have been quieter than rail lines a century ago (though I’m not sure if this is even true), the technology has surely shifted in rail’s favor with regards to noise. And even if the technologies were equally obtrusive on a per-mile basis, you much fewer less elevated rail miles to transport the same amount of people as with an elevated highway – perhaps even almost an order of magnitude less.
From Downtown:
John A. Miller was one of the few Americans who was puzzled by the construction of elevated highways. “Elevated railways with a capacity of 40,000 persons per hour in one direction are [being] torn down,” he wrote in amazement in 1935, “while elevated highways with a capacity of 6,000 persons per hour are being erected.”
Thankfully, we appear to no longer be considering urban highway expansion. Urban rail expansion shouldn’t be off the table, however, thanks to the ill-advised highway expansions of the past.
In a brief series of posts, I wanted to take a visual survey of elevated rail precedents around the world. My work here is by no means exhaustive; I welcome any feedback you might have.
Index of posts in the series:
- Prologue
- Part 1 – The universe of post-tensioned pre-cast concrete
- Part 2 – Best practices of integrating viaducts into urban designs
- Part 3 – Els that gave Els a bad name
- Part 4 – Monorails, active uses under viaducts, and precast concrete in Puerto Rico
- Part 5 – Vancouver and Tysons Corner
- Part 6 – Hong Kong