NPR Here & Now – The Economics For And Against Trump’s Infrastructure Plan

I will be on NPR’s Here & Now on today’s episode talking infrastructure.

A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King
A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King

One area where Democrats are hoping to work together with President-elect Donald Trump is infrastructure.

Before he was elected, the Trump team put out a proposal for infrastructure that would include public-private partnerships and tax credits for companies to invest in roads, bridges and more.

Here & Now‘s Robin Young speaks with University of Minnesota professor David Levinson (@trnsprtst) about the economic arguments for and against such a plan, and why infrastructure shouldn’t be thought of as a jobs program. Levinson is also author of the book “The End of Traffic,” and writes the Transportist blog.

Update: Audio Available (download) or stream

U study says transit does not have impact on public health

While many click-bait articles have headlines that claim using public transportation has a significant impact on health, a University of Minnesota study, which explored the correlation between transit and public health, found that there was no significant evidence showing that using public transit improves health.

“For the last 10-15 years, people have been saying they want people to be walking or using transit because there is a significant health benefit,” said David Levinson, University transportation studies senior research associate and co-author of the study.

“It may or may not be true, but it’s a very weak correlation.”

There is an idea that commuters are a more healthy population due to the fact that they use public transit, Levinson said.

Transit is often associated with walking or biking. Previous studies have found that citizens in areas with more transit options have a lower BMI.

But using BMI for that conclusion doesn’t account for commuters who may eat fast food every day or substitute buses and trains for walking from place to place, Levinson said.

Ultimately, the researchers found transit did not have a significant impact on public health.

Alireza Ermagun, University urban and regional planning Ph.D. candidate  [sic – he got a PhD in Civil Engineering, he was also a MURP] research assistant and co-author of the study, said he wanted to point out problems with associating insignificant correlations to data and making assumptions not backed up by sufficient research.

Researchers often rely on data they already have to draw conclusions because research is expensive and difficult to compile, he said.

For example, the researchers analyzed the height of transit users relative to their location because other researchers often correlate travel method and body mass index. They found that people were shorter in locations like cities, where transit was more readily available.

This could justify the claim that transit makes you shorter, he said.

“People are too quick to use these results to draw conclusions,” Levinson said.

But Ermagun said he hopes this study will caution future researchers from making assumptions about their data based on exaggerated connections.

“The result of this study helps people gain a clearer view,” he said. “It allows them to put these resources in a more effective direction.”

Elizabeth Wrigley-Field, [ed. note, apparently a real person] sociology assistant professor, said researchers often try to narrow down one specific way to improve public health.

“There is a lot of tendency in the topic of health to focus endlessly on things that actually make a small difference,” she said. “Like exactly what fruit we should be eating or what exercise we should be doing.”

Instead, Wrigley-Field said promoting larger-scale research would be a more efficient means to improving health through initiatives like reducing air pollution, combating poverty and eliminating food insecurity.

“The relative lack of attention to these topics isn’t a lack of knowledge,” she said, “but a lack of political will to talk about them.”

Elements of Access: Hierarchy

In binary networks, the focus is on whether or not a connection between two nodes exists.  However, not all links (or nodes) are created equal, particularly when it comes to transportation networks.  When we know about the presence of a link as well as the strength of that link, it is called a valued network.  For instance when traveling from A to B in a street network, there is usually discontinuity in street type.  In other words, one might move from a local street to a collector road to an arterial road and then back to a collector before reaching their destination.  While engineers know this sort of differentiation as functional classification, it is also referred to as hierarchy.


Hierarchy, which is embedded in many natural and societal systems such as biologic cells and the Internet, is a common transportation complexity that requires a more complicated topological analysis (Tomko, Winter, & Claramunt, 2008).  Typical topological measures such as Degree or Betweenness can be useful in helping understand network hierarchy, particularly in tree-like networks; however, such measures would fail to properly distinguish between streets in a gridded street network.  In the above version of Metropolis’ street network, the major streets are represented by thicker lines and easily discerned, even in a gridded network (Fleischer, 1941).   Using the basic set of topological metrics, we would have no idea that 8th Street is functionally different from 7th Street or F Street from D Street.  These metrics fail to consider attributes – such as urban design, number of lanes, active transportation infrastructure, adjacent land uses, and speed – beyond network structure and would not necessarily be able to distinguish such streets.

Elements of Access: Transport Planning for Engineers, Transport Engineering for Planners. By David M. Levinson, Wes Marshall, Kay Axhausen.
Elements of Access: Transport Planning for Engineers, Transport Engineering for Planners. By David M. Levinson, Wes Marshall, Kay Axhausen.

Working with hierarchical networks often involves dividing networks in multiple layers or tiers.  Measurements of heterogeneity have also become common proxies for characterizing hierarchy.  To identify heterogeneity among street segments, researchers have used entropy measures as well as discontinuity measures (Xie, 2005).  Discontinuity, for example, does not necessarily denote a disconnected network; rather, the reference is to the discontinuity in moving from one street type to another.  If we sum the number of times a traveler goes from one type of street to another while traveling along a shortest path route, we find the trip discontinuity.  Dividing that number by the length of the trip gives us the relative discontinuity (Parthasarathi, 2011).  Other simplistic hierarchy measures calculate the relative percentage of a particular type of road.  For instance, we might divide the number or length of arterials by the total number or length of roads to find the relative percent arterials (Parthasarathi, 2011).


Interestingly, it is not uncommon for large-scale transportation models to delete streets on the lower end of the hierarchical spectrum (i.e. local streets) for the sake of computational efficiency.  Yet, removing such streets creates a bias against more connected networks because less connected networks typically need to be supported by major streets with more capacity than would be needed in more connected networks (Bern & Marshall, 2012).  Some topological researchers – where the focus should be on understanding the full network – unfortunately reach the same conclusion: “urban streets demonstrate a hierarchical structure in the sense that a majority is trivial, while a minority is vital” (Jiang, 2009).  If we only care about vehicle traffic flow, such statements may be true.  However, my previous street network research confirms that understanding the full network holds the key to pushing toward improved safety, increased active transportation, and better environmental and health outcomes (Bern & Marshall, 2013; Marshall & Garrick, 2009, 2010a, 2010b, 2012).

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