Unclear why this paper is receiving so much attention when it has numerous weaknesses such as:
• The title "Transit makes you short" is misleading, because it suggests causation between transit and height, yet one of the critical messages (somewhat buried in the paper) is that association and causation are not the same.
• The authors correctly cite a number of studies that found an association between transit and health. Then they describe an opposing viewpoint, for which there is little evidence, suggesting that transit could be unfavorable toward health. They cite one study from London in which young adults given free bus passes substituted transit use for walking and biking. This study is not generalizable because it examines free bus passes rather than usual paid transit use found in most cities, and it studies only one age group.
• Another reason to think that transit is unlikely to substitute for walking and biking is that most walking trips are less than half a mile and bike trips are commonly less than 2 miles. Transit trips are usually at least several miles, so one would expect transit to rarely substitute for walking and biking. Transit is unlikely to be a substitute for short distance walking and biking because transit involves a waiting time; often for a short trip it becomes faster to walk or bike then to wait for the transit. Also for short trips it is probably infrequent the transit goes from exactly the origin and destination that are needed.
• The strongest claim for an association between health and transit relates to transit and physical activity, because most transit trips begin and/or end with walking. Whether transit can be shown to have an effect on overall health or on body mass index is less important, because general health status and body mass index are due to many factors, not just physical activity. A documented increase in physical activity from transit is a sufficient public health reason to encourage transit use.
From: h+t--friends-bounces@chrispy.net [mailto:h+t--friends-bounces@chrispy.net] On Behalf Of mbrenman001@comcast.net
Sent: Thursday, December 01, 2016 7:24 AM
To: h+t--friends@chrispy.net; thomas.goetschi@uzh.ch
Subject: Re: [H+T--Friends] Antwort: 'Transit Makes You Short'
What is "the power of large sample"? And of course correlation is not causality. One can imagine that in the us, transit riders are shorter than car driver s, because of ethnic difference s in users. And there have been various studies showing a correlation between height and higher pay, partly due to gender disparities.
Marc brenman
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-----Original Message-----
From: thomas.goetschi@uzh.ch
To: h+t--friends@chrispy.net
Cc:
Sent: 2016-12-01 6:48:32 AM
Subject: [H+T--Friends] Antwort: 'Transit Makes You Short'
this may have some value for a journal club - I see flaws at various levels. How it may contribute to our understanding of any possible relationship between public transport and health escapes me.
Thomas Götschi, PhD
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Bewegung und Gesundheit / Physical Activity and Health
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_____________________________________________________________Ann Hartell ---12/01/2016 12:14:34 PM---I'm not sure how many on this list follow David Levinson's blog The Transportist (over here: https:
Von: Ann Hartell <ahartell@gmail.com>
An: TRB Health and Transportation <h+t--friends@chrispy.net>
Datum: 12/01/2016 12:14 PM
Betreff: [H+T--Friends] 'Transit Makes You Short'
Gesendet von: h+t--friends-bounces@chrispy.net
I'm not sure how many on this list follow David Levinson's blog The Transportist (over here: https://transportist.org/ ), but he recently published a post about a working paper he co-authored with Alireza Emragun titled "Transit Makes you Short": On Health Impact Assessment of Transportation and the Built Environment.
The blog post is here:
https://transportist.org/2016/11/28/u-study-says-transit-does-not-have-impact-on-public-health/
The full paper is here:
http://conservancy.umn.edu/handle/11299/179812
Abstract:
The current research provides a test framework to understand whether and to what extent increasing public transit use and accessibility by transit affect health. To this end, the effect of transit mode share and accessibility by transit on general health, body mass index, and height are investigated, while controlling for socioeconomic, demographic, and physical activity factors. The coefficient-p-value-sample-size chart is created and effect size analysis are conducted to explore whether the transit use is practically significant. Building on the results of the analysis, we found that the transit mode share and accessibility by transit are not practically significant, and the power of large-sample misrepresents the effect of transit on public health. The results, also, highlight the importance of data and variable selection by portraying a significant correlation between transit use and height in a multivariate regression analysis. What becomes clear from this study is that in spite of the mushrooming interdisciplinary studies in the nexus of transportation and health arena, researchers often propose short- and long-term policies blindly, while failing to report the inherent explanatory power of variables. We show that there is a thin line between false positive and true negative results. From the weakness of p-values perspective, further, we strove to alert both researchers and practitioners to the dangerous pitfall deriving from the power of large- samples. Building the results on just significance and sign of the parameter of interest is worthless, unless the magnitude of effect size is carefully quantified post analysis.
~~~~~~~~~~~~
Ann Hartell
Doctoral Candidate
Institute for Multi-Level Governance and Development
Wirtschaftsuniversität Wien/Vienna University of Economics and Business
https://www.wu.ac.at/en/mlgd/
Personal: annhartell.com
Email: ahartell@gmail.com_______________________________________________
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