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Counting Tire-related Crash Deaths,
1992 through 2017


Fatal, tire-related crash.

Problem Solving by Official Statistics

It has been difficult to measure progress in reducing tire-related crash deaths in the United States because the full scope of the problem has been misrepresented by the federal agency chiefly responsible for motor vehicle safety, the National Highway Traffic Safety Administration (NHTSA).

Until October 2018 NHTSA promoted a sample-based estimate of the number of persons who die in tire-related crashes as "almost 200" yearly since the Agency's tire safety rulemaking in 2014. Based an actual census of such events, NHTSA's own Fatality Analysis Reporting System (FARS), this was a gross underestimate.

NHTSA's official view in 2014 that there had been a 50 percent reduction in tire-related deaths during 2007-2010 compared to 1995-2006 was also unlikely to be true. Not only was the estimated reduction produced without any publicly documented assessment of its sample error, the claimed reduction was at odds with changes in the actual numbers of tire-related deaths known from FARS. Even so, NHTSA cited this implausibly large reduction in tire-related fatalities as an important reason to halt regulatory action pending at that time related to tire safety.

At the invitation of the National Transportation Safety Board (NTSB) in December 2014, we presented the results of a study funded by The Safety Institute of Rehoboth, Massachusetts to the Board. Our study showed that NHTSA's fatality estimate undercounted the actual number of deaths in tire-related crashes by about two-thirds. Following our presentation, the NTSB reported a far higher count of deaths for 2013 (539) in its "Annual Report to Congress 2015" than the official summary from NHTSA ("almost 200"). Yet even this embarrassment did not cause NHTSA to change its official statistics about casualties from tire failures.

In 2014 we made many recommendations to the NTSB regarding statistical analyses of tire safety. For example, we suggested that the NTSB ask NHTSA to reconsider NHTSA's tire aging rulemaking based on accurate casualty counts of tire-related deaths and injuries in U.S. motor vehicles. We also recommended that NHTSA count tire-related crash deaths based on its census of fatal motor vehicle crashes rather than on an estimate from a probability sample with a large sample error. It was later revealed that the sample errors for NHTSA's estimates were so large that 95% confidence intervals included zero deaths for passenger vehicle occupants in tire-related crashes.

Years passed. NHTSA's official estimate of tire-related crash deaths stayed put at "almost 200."

That has now changed.

For reasons that are unclear, NHTSA is currently presenting to the public a much more candid assessment of tire-related deaths based on the fatality data it chose to ignore in 2014. As of November 5, 2018, the Agency reported that there were 738 "total motor vehicle traffic fatalities in 2017 in tire-related crashes." The magnitude of the difference in fatality counts (738 compared to "almost 200") calls for a re-examination of NHTSA's 2014 rulemaking analysis.

Reanalyzing the Data

NHTSA's 2014 decision was oriented to a light vehicle tire standard. For this reason, we reanalyzed FARS crash data involving tire-related issues in light duty passenger vehicles only. Also, the Agency choose to study tire-related casualties during the period 1995-2006 compared to 2007-2010. For the sake of consistency, we do the same here while adding some additional analyses for the period 2011-2017. 2017 is the last year for which FARS data were available at the time of this study.

Our present research shows that there were 582 fatalities in 2017 in the subset of crashes involving tire factors recorded for light duty passenger vehicles. This figure is based on the same underlying data that is now apparently used by NHTSA and it is consistent with NHTSA's currently publicized figure related to tire factors in crashes involving all types of motor vehicles. (Our count, however, is based on a slightly different method that utilizes more of the specific data related to tires that is available in FARS. See R. A. Whitfield and Alice K. Whitfield, "Quantifying Tire-related Deaths and Injuries in U.S. Motor Vehicles", slides 40 and 41.) Included in the 582 deaths are fatalities of all persons in tire-related crashes involving passenger vehicles, such as pedestrians struck in a crash sequence following a tire failure. Also included are any vehicle occupants killed in a multi-vehicle, tire-related crash of a passenger vehicle. NHTSA's new official figure also takes this same, inclusive approach.

Based on the FARS data since 1992, fatalities in crashes involving light passenger vehicles with tire-related issues have slowly decreased since 1992. Unfortunately, the average change is only 7 fewer deaths per year. Tire-related deaths have exceeded 500 per year in almost every year during this 25 year period. The total during this time is 16,381 tire-related fatalities.

Fatalities in Crashes Involving Light Passenger Vehicles with Tire-related Issues,
1992 through 2017.


Time Series of Tire-related Crash Deaths

There was a 14 percent reduction in the average annual counts of tire-related deaths involving crashes of passenger vehicles from 660 in 1995-2006 to 565 in 2007-2010. Of course, this result not consistent with the 50 percent reduction that NHTSA claimed in 2014 to support its decision to abandon rulemaking related to tire safety. And it is important to note that the average annual count of tire-related deaths involving crashes of passenger vehicles actually rose 6 percent from 565 in 2007-2010 to 598 deaths in 2011-2017.

NHTSA's decision in 2014 is also not consistent with the fact that non-tire-related crash fatalities involving passenger vehicles were decreasing faster than tire-related fatalities during the periods they studied. Based on the FARS data, we calculate that the average annual count of fatalities in crashes involving at least one passenger vehicle but without known tire-related issues involving those passenger vehicles decreased 18 percent from 38,215 in 1995-2006 to 31,413 in 2007-2010. This count fell again over the period 2011-2017 by 6 percent to 29,600. At the same time, the corresponding totals of tire-related deaths was rising by 6 percent.

Suggestions that the apparent failure to reduce tire-related fatalities is an artifact of a change in the way that the underlying data in FARS are reported since 2010 are not supported by the data. (See slides 53-56 of our study.) Tire-related fatalities in the United States do not appear to have to have been substantially reduced since the NTSB's Tire Safety Symposium in 2014.

Moving Forward

NHTSA should review past rulemaking decisions for tire safety that were based on data and methods that are known to be unsuited to a statistical study of this topic. The Agency's review of its rulemaking should be based on scientifically plausible casualty counts of tire-related deaths and injuries – such those it now presents to the public.

Questions?

To inquire about our research, please to send us an email.

Acknowledgement

This project builds on past research supported by The Safety Institute of Rehoboth, Massachusetts, a non-profit organization dedicated to injury prevention and product safety.

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