Sunday, January 22, 2012

What does it mean to "support transit"?

Last week I singled out Richard Layman for repeating the chestnut "Spain doesn't have the population density to support economically many of the lines, based on ridership." Again, let me make clear that Richard is far from alone in assuming that density is required to support transit, and that his blog is informative, insightful and well worth reading for urban issues. He was also a good sport in leaving a comment on my post; unfortunately all the comments made it clear to me how deep the idea is ingrained in our understandings of transit.

A number of people have addressed this issue before. Richard mentions Steve Belmont and linked us to a scan from his book (see also David Alpert's take). Alon mentions Gary Barnes and his concept of "perceived density" (PDF); the Austin Contrarian has his own idea of perceived density.

I had a great idea for a phrase, "density is not destiny," but like most ideas it turns out that someone's thought of it before you; in this case it was Paul Mees, and Jarrett has an interesting discussion. But all these discussions are frustratingly myopic, assuming that the competing road network is a constant force of nature beyond political influence.

Instead of looking at the concept of "density," let's look at "support." What does it mean to support a transit line? Is it complete financial self-sufficiency, as Germà Bel demands for the Spanish high-speed network? If that's the case, then very few transportation projects anywhere would qualify. Is it the simple existence of the transit line? Then Newburgh's three-line transit system would qualify, since it exists, but that's not a very enlightening criterion. Is it a certain threshold of mode share, as the discussion at Greater Greater Washington would suggest? That's more promising, but it's not all.

Let's bring in some Strong Towns thinking. Chuck Marohn looks at any transportation project and asks, what is the return on investment? And it turns out the answer is connected to density. The ROI for a street, bus line, train line or ferry dock, it turns out, is dependent on the benefits derived from that investment. If it's a government investment, it has a "public ROI" indicating the benefits accrued to the public, whether in the form of tax revenue or any other goal.

ROI is the benefits divided by the costs. In transportation, sewers, utilities and other public projects, the costs are spread out geographically, so the ROI depends on the density of the benefits. That is where density comes in.


Pantograph Trolleypole said...

This question has been intriguing me lately. As Zupan/Pushkarev mention in their seminal work, there's a pretty low density for corridors that support rapid transit. What ultimately matters more they believe is the place that people are going. The size and density of the downtown or destination employment center is much more of a factor in attracting riders than the residential end density.

When we think about HSR, we also have to consider that unlike airports, the destinations are mostly downtown. I believe whole heartedly that California for example, when through with high speed rail will bump up the value of developing more densities in downtowns. What this does as an aside is make regional transit more important as well as strengthening regional productivity. I don't know if you saw the Cleveland Federal Reserve report. But it makes an interesting observation about cities. Those which grow or stabilize their cores are much healthier than those which don't.

Richard Layman said...

well, I am not just sure what you're arguing.

When I talk about density, what I mean is a lot of people proximate to each other.

I don't necessarily mean lots of tall buildings.

In my writings on "metropolitan mass transit planning" I discuss the need to define network breadth, depth, LOS, and LOQ in a plan separately from how a transit operator would do so.

I mention this only because issues of network breadth and depth mean providing service in places that wouldn't pencil out economically if you forced every line to be revenue neutral or positive in terms of economics.

I mentioned Belmont because of his argument about recentralization.

My focus, including the blog, on what I term "revitalizing and repopulating central cities" leads to my focus on density.

As far as population density goes, I don't see how you can't have it, and make transit work.

Germà Bel said...

Just a few words to make clear one thing: Transit infrastructure and services can provide different benefits. Those that are internalized by users should be paid for by them (unless making users pay is too costly because of administration costs). Those that are of external character (externalities) can justify financial subsidies/surcharges to the infrastructure/services, thus contributing to support the line (if subsidies finally apply). This is a clear rationale for not asking for complete financial self-sufficiency from, for instance, metropolitan transportation services, or basic infrastructure services that prevent urban communities from remaining isolated. There is not such a case for HSR. In any case, the issue can be taken to a CBA analysis to establish the SOCIAL return from the investment (financial + economic + externalities), including potential reduction of congestion in alternative modes, potential reduction of accidents, potential reduction of pollutants emission (in this case, taken as well into account the pollutant emissions caused by the HSR line construction), etc. A good illustration for this type of analysis is provided in the work you will be able to find linked here, for the Italian HSR.
Germà Bel

t0wnp1ann3r said...

The sheer fact that I know half the names since I read their blogs immediately causes me to wonder if I'm following (but not a part of) an amazing group of urban thinkers, or if instead maybe I've gotten caught up in a specific subset group think...