A little knowledge…

A Texas TV station attempting to educate the public has instead misled the public (warning: autoplay video).

People in Vidor, Texas thought there were more crashes on I-10 since the speed limit went up. A KBMT investigator checked accident records. There were 130 crashes in 2010 and 180 in 2016, so the crash rate went up after the speed limit went up.

That’s at best misleading. The speed limit increase was in early 2012. Let’s look at the complete data set used for the report:

Year 2010 2011 2012 2013 2014 2015 2016
Crashes 130 77 100 109 109 115 180

The average crash rate for two years before the speed limit increase was 104 per year. For two years after it was 109. Those figures are statistically equivalent; you expect even more year-to-year fluctuation than that, and traffic was increasing. Only in 2016 did the highway become more dangerous.

The report linked to the Texas DOT crash report tool. (KBMT does deserve credit for providing that link.) The web site is very useful. I used it to find two important facts left out of the report.

First, about a quarter of the crashes reported on “I-10” were really on the frontage roads. The speed limit there is 55 or less.

Second, 106 of the 180 crashes in 2016 were in a construction zone compared to 12 of 115 in the year before.

What do you think — did the speed limit increase do nothing for four years then cause a spike in accident rates, or did road construction during 2016 have an effect that same year?

The opinions expressed in this post belong to the author and do not necessarily represent those of the National Motorists Association or the NMA Foundation. This content is for informational purposes and is not intended as legal advice. No representations are made regarding the accuracy of this post or the included links.

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