Background

Over the years there have been a number of fatal 15-passenger, single vehicle, rollover accidents which were initiated by a failure of one of the tires. In many cases the tire failure was in the form of either complete or partial tread separation causing the driver to lose control of the vehicle and resulting in a rollover. From 1997 through 2006, there were 534 fatalities of 15-passenger van occupants resulting from 312 single vehicle rollover accidents. Of those, tires were identified as a related factor in 61 of the accidents and 95 of the fatalities.[1]

In 2007, NHTSA issued a research report to Congress on tire aging (DOT HS 810 799). In that report, they state that “it is difficult to estimate, based on crash statistics currently available, how many crashes are caused specifically by tire aging. However, we know that tire aging is a significant factor in tire related safety”.[2] As a matter of fact, several vehicle manufacturers now recommend a maximum six year service life for tires on their vehicles … including the spare.[3]

In a recent study conducted by North Carolina State University, only 4% of those surveyed identified “aging” as a potential tire problem.[4] Indeed, most people identify “tread depth” as the measure of tire life and safety.

Many 15-passenger vans are owned and operated by Churches, Colleges & Universities, Communities Centers, etc. and are not used on a daily or in some cases even a weekly basis. If the annual mileage is low, the possibility exists that the tires could exceed their safe useful life by age in lieu of loss of tread depth.

According to one set of data from R.L.Polk and Company, there were 517,665 15-passenger vans registered nationally in 2006 … of those, 9,929 were registered in Tennessee.[5] Additional data from R.L.Polk and Company indicated that, as of July 1, 2006, there were 557,046 15-passenger vans registered in the US.[6]

This study was undertaken to obtain real data on actual mileage of 15-passenger vans and to obtain data on the age of tires installed on those vans.   

Data Collection

From mid February, 2008 through early April, 2008 data was collected from a variety of 15-passenger vans in Knoxville, Tennessee. The method was to randomly drive around the Knoxville area in search of 15-passenger vans. Once a van was found there was an attempt to find the owner to distribute van safety information and to obtain permission to record data from the van. In most cases the van VIN number was recorded along with the mileage and the tire manufacturing date from the tire TIN number. This data was then entered into a spreadsheet for analysis and charting.

Data from three vans involved in fatal accidents not in the Knoxville area were also included in the study. Data for two of those vans was obtained from a NTSB Accident Report (NTSB/HAR-03/03) … “15-Passenger Van Single-Vehicle Rollover Accidents, Henrietta, Texas, May 8, 2001, and Randleman, North Carolina, July 1, 2001”.  Data for the third van was obtained from the accident report for the 15-passenger van, single vehicle accident that occurred near Columbia,  South Carolina that resulted in the death of Alexis James on July 17, 2007.

Data was collected for a total of thirty two 15-passenger vans.

Findings

The distribution of the ages of the vans included in this study are very similar to the overall national average. Thus, a case might be made that the actual data collected may be representative of all 15-passenger vans in the US.

The average age of the vans in this study is 10.5 years vs. a national average of 12.5 years as of 2006.[7]

Tire ages were recorded for 30 of the vans as follows …

40% of the vans had tires that were six or more years old. Over 30% of the vans had tires that were eight or more years old while over 20% of the vans had tires that were over ten years old.

Looking at only the vans that are 10+ years old, approximately 60% of these had tires that were eight or more years old while approximately 46% had tires that were ten or more years old.

Mileage was recorded for 28 of the vans. The estimated annual mileage was calculated by dividing the total mileage by the van’s age in years based on the model year.

Conclusions

1. Based on the data collected approximately 23% of all 15-passenger vans have tires that are ten or more years old. According to the NHTSA research report on tire aging, ten years is the maximum service life recommended by the tire manufacturers.[8] Applying this to the total number of 15-passenger vans registered in the US, it can be estimated that approximately 110,000 to 120,000 of the 15-passenger vans on the road today might have tires that are ten years old or older … this is considered beyond the maximum safe service life by the tire manufacturers and thus at risk of failure by aging.

2. Several of the documented single rollover accidents that occurred in the southern states involved tires that were eight or more years old. It is believed that the higher temperatures in the southern states accelerate the tire aging process.[9] Southern states, including Florida, South Carolina, Georgia, Alabama, Mississippi, Louisiana, Texas, Arizona, New Mexico, Nevada and California, had a total of 188,000 15-passenger vans registered in 2006.[10]  The data collected in this study showed that approximately 33% of all the vans had tires that were eight or more years old. Based on this it can be estimated that approximately 60,000 of all the 15-passenger vans in the southern states listed might have tires that are at possible risk of failure due to aging.

3. The data collected indicates that the general public who own and operate these vans are unaware of the dangers of aged tires. The vast majority believe that safe tire life is based only on tread depth. Thus tires are in service until the tread depth reaches the recommended minimum or until severe cracking or other visible deterioration is evident. The data collected indicated that on average these vans are driven approximately 6,600 miles per year. This is less than half the national average for all passenger vehicles. Most OEM tires have a tread life of at least 60,000 to 70,000 miles. Thus if one only looks at tread depth, it is easy to see that even well meaning, observant van operators could keep tires on their vans for over ten years.

4. Considering the estimated 15-passenger van average mileage driven per year ,,, the number of 15-passenger vans registered … and the number of 15-passenger van occupant fatalities per year,

one can calculate the 15-passenger van fatality rate per 100M VMD.

 This table shows the results of that calculation for the years 2005 and 2006 and compares those number with the actual numbers for all passenger vehicles for the same two years.  

This indicates that even though the fatality rate for 15-passenger vans has declined significantly, it is still 20% higher than the national average for all passenger vehicles. Thus the 15-passenger vans can still be considered one of the most deadly vehicles on the road today.

Recommendations

1. Request NHTSA to conduct a nationwide survey to confirm or perhaps to dispute the data collected in this report in the Knoxville area.

2. Based on the outcome of that nationwide survey, request NHTSA to issue an alert to all owners/operators of 15-passenger vans regarding the dangers of tire aging … include instructions as to how to determine tire age and recommendations for maximum service life.

3. Continue to encourage NHTSA to improve the Federal Motor Vehicle Safety Standards and to continue to extend those standards to 15-passenger vans.

4. Continue to distribute the attached 15-passenger vans Safety Guidelines to the owners and operators of the vans … and encourage compliance with the Safety Guidelines.

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