Twice in the past five months, the online site The Atlantic Cities has posted articles touching on a recurrent question: If you build light-rail lines, will they reduce congestion on the roads?
In the latest piece, contributing writer Eric Jaffe reports on a recent study showing that the Denver region’s three light-rail corridors have reduced the rise in motor vehicle traffic on nearby highways. I regard Jaffe's article as a two-cheers-for-rail kind of assessment. Rail transportation evidently prevented highway congestion from worsening as much as it might have, but that’s hardly something people will shout about.
The Denver report follows up on Jaffe’s blog post last October about two University of Toronto economists who determined that an increase in public transit capacity “is unlikely to relieve congestion.”
According to Jaffe, serious studies of the congestion issue have come to opposing conclusions. Some researchers, like Todd Litman at the Victoria Transport Policy Institute, have discovered that a good rail transit system can in fact reduce congestion on the roads. Others, like the Toronto economists Gilles Duranton and Matthew Turner, have confirmed what they say is a “fundamental law of road congestion”: Motorists will fill the available roads whether you build more roads or build more transit or do nothing.
All of this is interesting, but in my view, Jaffe’s focus on the transit-and-road connection isn’t helping Americans to understand what matters most about transit and cities.
What the studies say
I looked up Duranton and Turner’s research paper in the October 2011 American Economic Review, and all I can say is: It’s not written in a fashion that makes the situation clear. The two economists argue that if you build roads, the roads will attract traffic. And if you keep building additional roads, people will drive even more—even if you making transit available as an alternative.
As for proving their points, a reader lacking a PhD in economics or mathematics pretty much has to take Duranton and Turner’s conclusions on faith; the research paper is full of passages like this:
To motivate our econometric strategy, consider a simple model of equilibrium VKT. To begin, let R denote lane kilometers of roads in a city, let Q denote VKT, and let P (Q) be the inverse demand for VKT. The downward sloping line in Figure 1 represents an inverse VKT demand curve for a particular city.
In other words, their argument rests largely on obscure equations. Nowhere in the 36 pages (roughly 20,000 words) do we learn about the experience of a specific city or a group of cities. Instead we get out-of-left-field historical background (the spread of railroads in the 1800s; the 1972 presidential election as a predictor of public transit appropriations) and sentences like this:
The fundamental law of road congestion requires that each MSA have an intrinsic natural level of traffic conditional on lane kilometers of roadway.
Frankly, I’m surprised that Jaffe places so much faith in “research” that so insistently defies comprehension. I don’t think the two economists have proved a thing.
A clearer alternative
Litman’s report for the Victoria Transport Policy Institute (VTPI), Rail Transit in America: A Comprehensive Evaluation of Benefits, is cut from an entirely different cloth. It looks at the experience of actual cities and metro areas, such as Portland, Oregon, and presents interpretations that a reader can understand.
Since 1980, when it decided to build its first light-rail line, the Portland region has constructed a growing rail network. Since 1990, rail ridership there has more than tripled, Litman observes. The expansion of rail transit is part of the reason, he says, that per capita vehicle travel in the Portland region has declined in recent years; it’s now about 15 percent below the national average.
In the report, issued in January of this year, Litman says that transit, in the right circumstances, can reduce road congestion. A key element is this:
Once a roadway reaches capacity, even a small reduction in volumes can significantly reduce delays. For example, a 5% reduction in peak-hour traffic volumes on a road at 90% capacity can reduce delay by 20% or more. Transit can provide significant congestion reduction benefits, even if it only carries a small portion of regional travel, because it offers an alternative on the most congested corridors. Reducing just a few percent of vehicles on such roads can significantly reduce regional congestion benefits.
In another January 2012 study, Smart Congestion Relief, Litman emphasizes that current demographic, geographic and economic trends— an aging population, rising fuel prices, increasing urbanization, changing consumer preferences, and increasing health and environmental concerns—are reducing growth in automobile travel demand and increasing demand for alternative modes: walking, cycling, ridesharing, and public transit.
Advocates of transit have sometimes overemphasized congestion as a rationale for building rail lines. That may help explain why Jaffe, at Atlantic Cities, has paid so much attention to the question of whether light rail provides congestion relief.
My view—and that of many others in the New Urbanism/smart growth movement—is that congestion relief is only one of the many reasons why rail transit is a worthwhile investment in cities and regions of a certain size. I asked Norman Garrick, a transportation specialist at the University of Connecticut, about the congestion-transit discussion. He replied:
The important point [about a robust transit system] is that the city benefits immensely on numerous fronts from the reduction in vehicle traffic: less space for roads and parking, less noise and pollution, lower energy use for transportation, better financial footing for the transit, and overall, lower travel cost in the city, not to mention the economic competitiveness of the city versus the suburbs on so many levels.
A single-minded focus on congestion really just leads to frustration. ... if the transit itself is sold just as a way to reduce congestion, it tends to end up being designed badly. ... this is the case in Denver, where many of the transit lines were simply plonked down on freeway corridor and will do little in changing the city’s character over the long run. In contrast, streetcar in [Washington] DC is being designed in a much more deliberate manner that recognizes all the potential benefits to the city of well-designed and located transit.
Jeffrey Tumlin, author of Sustainable Transportation Planning (the new book is extensively reported on in the March print issue of Better! Cities & Towns, soon to be distributed), made these points in an e-mail to me:
Great cities do not invest in rail systems in order to reduce congestion; they invest in rail systems in order to grow their economies with less congestion than they would get if they had invested in roadways instead. They invest in railways because they are a more space-efficient and cost-effective means of moving people under certain urban conditions, and because the real estate market responds with a higher level of investment along a rail corridor ... again under the right conditions.
Rail upgrades development
In Portland, Litman notes, the introduction of rail service has done much to encourage compact, mixed-use development within walking distance of the stations. This transit-oriented development further cuts the need to drive or own cars. It reduces highway demand. There’s a mix of ingredients, some of them subtle, that together can propel a region toward a generally more enjoyable and less wasteful way of life.
Litman explains how these mutually reinforcing factors work:
Rail transit tends to provide relatively high service quality; it is usually more comfortable, faster (particularly if grade separated), better integrated with other modes (walkable station areas, bike storage, park-and-ride facilities, and service to intercity bus stations and airports). Rail transit tends to leverage additional vehicle travel reductions by stimulating Transit Oriented Development (also called New Urbanism and Smart Growth), which consists of compact, mixed-use, multi-modal neighborhoods. ... Households in such areas tend to own fewer vehicles, drive less and use alternative modes more. As a result, rail transit usually attracts more riders within a given area, particularly discretionary riders (travelers who could drive, also called choice riders), and so tends to reduce per capita vehicle travel more than bus transit.
Rail benefits some urban areas more than it benefits others. Litman says rail transit “is particularly important in large, growing cities.” Large cities that lack well-established rail systems are at a disadvantage—in congestion costs, consumer costs, and accident risk—when compared to large cities that possess well-established rail systems, he observes.
“Rail transit can be a cost-effective investment in growing cities, provided it is supported with appropriate transport and land use policies,” he maintains. “Large cities with newer and smaller rail systems have not yet achieved the full potential benefits of rail transit, but, if their rail systems continue to develop with supportive public policies, their benefits should increase over time.”
So let’s have fewer discussions of whether rail systems reduce tie-ups on the highways. Traffic congestion is only a small part of the picture. What really matters is that rail systems, when well planned and when reinforced by other intelligent decisions, can improve the life of a metropolitan area in a huge variety of ways. That’s what we ought to be concentrating on.
For more in-depth coverage on this topic:
• Subscribe to Better! Cities & Towns to read all of the articles (print+online) on implementation of greener, stronger, cities and towns.
• See the January-February 2012 issue of Better! Cities & Towns. Topics: Value capture and transit, Social networks aid downtown, Live smaller, Rentals are market key, Streetcar inspiration, Box building, Civilizing suburbs, Alley houses, Sprawl repair, Healthy communities, Funding for infrastructure, Chicago River reversal.
• Get New Urbanism: Best Practices Guide, packed with more than 800 informative photos, plans, tables, and other illustrations, this book is the best single guide to implementing better cities and towns.
• See the December 2011 issue of New Urban News. Wall Street and urbanism, streets to plazas, Sustainable Communities grants, Choice Neighborhoods, TIGER grants, buyers prefer smart growth, protecting historic buildings, public health and planning, redevelopment in Georgia, Ecovillages, parklets.
• See the October-November 2011 issue of New Urban News. Topics: HUD’s Choice Neighborhoods; Parking reform, transit-oriented parking policy, Obama vs. Congress, West Virginia town revitalizes, suburb remakes its center, ecological dividend, cul-de-sac makeover, thoroughfare manual, and much more.