Public Transit Is Worth Way More to a City Than You Might Think
The Atlantic Cities
14 August 2013
Ph: Graphserver

In a new paper set for publication in Urban Studies, Daniel Chatman, Assistant Professor of City and Regional Planning at the College of Environmental Design, UC Berkeley and fellow planner Robert Noland of Rutgers University use concrete numbers to make the case that transit produces agglomeration.

Entitled "Transit Service, Physical Agglomeration, and Productivity in US Metropolitan Areas," the report surmises that this hidden economic value of transit could be worth anywhere from $1.5 million to $1.8 billion a year, depending on the size of the city. And the bigger the city, they find, the bigger the agglomeration benefit of expanding transit.

"These results could be dropped directly into a cost-benefit analysis," says Chatman. "It would show a higher benefits-cost ratio for rail investments, particularly rail investments in large cities with existing transit networks."

Any transportation mode that brings people to a certain place could promote agglomeration, but public transit makes it especially possible because it moves so many people within such a confined space. If workers can only get to a budding job center by car, for instance, eventually traffic will become so bad as to hinder growth. But if transit is also established in the same job center, then far more people will be able to access the area, and clustering there can advance accordingly.

"Whatever does happen in response to a transit investment is going to be concentrated," says Chatman. "You're going to have a different kind of urban form that springs up due to transit than due to the auto."

But with so many variables in play — from job density to population growth to transit development — studying agglomeration has been extremely difficult. So Chatman and Noland ran a number of statistical models that took into account all these factors, as well as economic productivity measures like average wage, for more than 300 metropolitan areas across the United States. ("It really is a new kind of thing we did here," says Chatman.) The numbers were so complex that many of the models failed to pass statistical muster. Those that did revealed a pretty clear line from transit expansion to economic growth via agglomeration.

Chatman stresses that because his method is so new, the results must be replicated before they're accepted. He also knows that some people will question the causality of the data: How can the researchers know, for instance, that transit alone is responsible for agglomeration? In response, Chatman points to the controls he and Noland installed in their statistical models — and to the fact that he's been critical of rail as an economic investment strategy in the past.

"Put it this way: I'm a skeptic on this stuff, and I was surprised to see these results so robust," he says.

If the findings do hold true, they mean that cities and transit agencies are underestimating the true benefits of public transportation. From there it's reasonable to expect all cities — though especially big ones — to base future requests for transit funding on the idea that agglomeration leads to economic productivity. If showing that system expansion leads to more riders and less congestion is good, and showing that it reduces pollution and improves public safety is great, then showing in big numbers how much economic growth will occur should be gold.