Recent headlines screamed at us:
Traffic Fatalities Up Sharply in 2015
NHTSA: 2015 Sees Largest Increase in Traffic Fatalities in Half Century
Highway Fatalities Jumped 7.2% Last Year
Cheap Gas May Be Killing Us
No, we didn’t make that last one up.
The media reacted swiftly to the National Highway Traffic Safety Administration’s (NHTSA) announcement that 35,092 people died on U.S. roads in 2015, an increase of 7.2 percent over the previous year. In turn, NHTSA and the White House made a public plea for help in analyzing the raw data to determine the cause of the near-record increase in highway fatalities.
You know that the instant conclusion of many will be – already has been – that speed limits have to be lowered.
First it should be recognized that two data points – in this case traffic fatalities in 2014 and 2015 – do not constitute a pattern. The second equally important observation is that absolute numbers are misleading when trying to identify a trend. NHTSA, by virtue of its FARS (Fatality Analysis Reporting System) database, established the standard by factoring in distance traveled. The traffic fatality rate in terms of 100 million vehicle miles traveled provides a truer year-over-year comparison than looking at absolute totals.
The reason is simple: As more total miles are driven, the risk exposure to accidents also increases. NHTSA noted that vehicle miles traveled were 3.5 percent higher in 2015 than in 2014. So while the agency estimates that total fatalities increased 7.2 percent in 2015, the fatality rate increase was actually 7.2 – 3.5 = 3.7 percent.
Check out this progression of numbers: 1.73, 1.69, 1.65, 1.58, 1.55, 1.53, 1.51, 1.51, 1.48, 1.44, 1.46, 1.42, 1.36, 1.26, 1.15, 1.11, 1.10, 1.14, 1.10, 1.08. Those are NHTSA-published fatalities per 100 million vehicle miles for 1995 (when the 55 mph national maximum speed limit was fully repealed) to 2014. The long-term trend is a steady decline in fatalities with the most meaningful year-to-year rate increase being 3.6 percent from 2011 (1.10) to 2012 (1.14).
That is similar to the increase between 2014 and 2015. Note that after 2012, the rate reverted back to the 20-year pattern of declining highway fatalities, 1.10 in 2013 and 1.08 in 2014. Let’s see what happens to the fatality rate in 2016, 2017 and 2018 before declaring a new upward trend based on a one-year increase.
That is not to say that efforts to reduce the absolute numbers of fatalities shouldn’t continue in earnest. It is commendable that the government is reaching out to tech companies for help in that regard. But when it comes to calls for blanket lowering of speed limits, consider this: From 1995 to 2014 speed limits rose from 55 mph to 70, 75 and even 80+ mph. During that same period, fatality rates dropped 37.6 percent in a relatively steady line. If anything, highway safety improvements across the nation should include speed limit reform where speed studies and the 85th percentile traffic engineering principle that can lead to a smoother, more consistent flow of traffic.