Data Does Not Support Claims that Light Rail Improves Rider Health

The Department of the Treasury and the Council of Economic Advisors recently released a new report titled “A New Economic Analysis of Infrastructure” that lists many different reasons to improve infrastructure. Some of the reasons are good, some bad, and others bizarre. But the most noxious claim is that transit usage improves public health. Despite the report’s spin, the cited studies do not reach that conclusion.

The report is split into four major sections that detail the Return on Investment, Investing in Infrastructure, Uses (for) Underutilized Resources, Supporting the Middle Class and Americans Want More Transportation Investment. (Note to the authors: Americans might want more transportation investment but they do not want to pay for it. Unless the transportation genie builds a beautiful new highway, finding the funds to build that highway will be challenging.) Report subsections include such fluffy topics as Building a National Community and Creating a More Livable Community. The report also proclaims that “Now Is The Time to Act.” I am waiting for one of these reports that says tomorrow is the time to act. The report also details the role of a merit-based national infrastructure bank. Perhaps the authors can explain a merit-based national infrastructure bank to the President, because he still does not understand the merit part.

The report has several good suggestions. The Next Gen section correctly notes the delays from our existing outdated aviation system. The Analytic Approach for Measuring Congestion details the high quality analytic work of the Texas Transportation Institute. (This study is about the only document that praises analytical work to come out of the Executive branch.) And it is hard to argue with building a Safer and More Reliable Infrastructure Segment.

But the most bizarre and inaccurate claim buried on page 24 of the report is the Public Health Benefits of Transit Investments. The section begins by saying, “If improved infrastructure changed the way Americans live and work, there would be significant benefits to health and wellness.” The report then details several studies that supposedly show this happening in the real world. I have always been skeptical of these claims; logically, walking more should improve your health; but there are often many other factors at play. Furthermore, justifying expensive transportation investments based on small health improvements is a very weak argument.

Quoting from the actual study:

Using data on individuals before (July 2006 to February 2007) and after (March 2008 to July 2008) the completion of a light rail system in Charlotte, North Carolina, they find that the use of light rail to commuter to work is associated with a nearly 1.2 point reduction in body mass index as well as an 81 percent reduction in the odds of becoming obese. Moreover, improved perceptions of neighborhoods as a result of the availability of light rail were associated with 15 percent lower odds of obesity as well as higher odds of meeting weekly recommended physical activity levels for walking and vigorous exercise.

First, this is one study in one metro area. The results in Charlotte, North Carolina may not be transferrable to other areas of the country. Second, the sample size is very low. Only 26 of the 498 people used light-rail transit (LRT) to commute to work on a daily basis. Although this 5.2% of the total population living in the area is statistically significant, making generalizations based on its small size is a bad idea. Third, there are several lurking variables that might affect the results. LRT users were three times as likely to be African-American as residents of the neighborhood as a whole. Different population groups have different rates of high blood pressure and diabetes. This is something that report should have taken into consideration. The LRT commuters are twice as likely to rent as opposed to own their houses compared with the neighborhood as a whole. Does this affect health or propensity to exercise? It might.

There are also several key limitations to this study. Quoting from the study:

There is likely substantial reporting error in estimates of these outcomes. For example, the measure of meeting vigorous RPA is likely high because of self-reporting bias. … Establishing the potential long-term effects of light-rail use on obesity will require subsequent follow up studies with larger samples of individuals that specifically measure walking distances through pedometers.

In other words, the study does not definitively report anything.

The second related study that the report quotes considered whether building new light-rail systems could be justified based on the potential health benefits. The study was rather blunt:

While these results suggest that there is a sizable public health benefit associated with the adoption of light rail, they also indicate that the effects are relatively small compared to the costs of constructing and operating such systems. These findings suggest that planning efforts that focus solely on the health impact of modifications in the built environment are likely to overstate the economic benefits.

In other words, the benefits do not exceed the costs.

The fact that the health part of the report was buried deep inside the contents indicates the Department of the Treasury realized that this is not the strongest part of the report. So why include it at all?

The Obama administration is on a mission to increase transit spending. It is throwing everything at the wall in hopes that some of it will stick. Since there is little quantitative data to support the administration’s claims, the administration is changing the New Starts rule so its pet projects can be evaluated by qualitative measures instead. My colleague Bob Poole has more details here. This administration decides what transportation policy it wants and then tries to find the data that supports that policy. The claim that light-rail transit improves public health is not supported by the cited studies.