Thursday, October 6, 2016

The Truth About Traffic: Putting Fatalities in Context

In my lectures, I often provide context about the risks associated with use of tobacco products by comparing those behaviors with the use of automobiles.  Putting risk in context is important, as can be demonstrated by focusing on traffic safety data alone.

The U.S. National Highway Traffic Safety Administration (NHTSA) recently reported that there were 35,092 traffic fatalities in 2015 – a small increase from the previous year (here).  Some media reports treated the incremental change as if it demonstrated a growing epidemic.  National Public Radio headlined their story, “Largest increase in decades” (here), and CBS called it the “Largest increase in a half century” (here).  Transportation Secretary Anthony Foxx said in a press release (here), “…far too many people are killed on our nation's roads every year…we're issuing a call to action and asking researchers, safety experts, data scientists, and the public to analyze the fatality data and help find ways to prevent these tragedies.” 

Reducing carnage is certainly a worthy goal, but NHTSA ought to kill the hype and present traffic fatality statistics in a meaningful fashion.  In past years, NHTSA framed fatality rates based on population (e.g., deaths per 100,000 residents) or on vehicle miles traveled (see Table 2 of last year’s report here).  Those rates are more meaningful than press release hyperbole such as, “2,348 more people died in traffic crashes compared to previous year.” (here) 

This year’s NHTSA report downplayed the miles traveled rate and omitted the population rate.  Fortunately, using Census Bureau data, one can calculate the latter.  The chart shows both rates since 2005.

Traffic fatality rates, after falling almost continuously for several decades, have been stable since around 2009.  The small 2014/2015 uptick to 11 deaths per 100,000 population or 1 billion miles traveled is not an increase of epidemic proportions.

The risk of traveling by automobile in the U.S. remains very small.

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