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Tire Known Unknowns: Decoding the Date

Human Factors researchers at the State University of North Carolina have recently concluded that consumers can’t read the date of manufacture obscured by the week and month configuration dictated by the Tire Identification Number (aka the DOT number).

Researchers Jesseca Taylor and Michael Wogalter asked 83 test subjects to translate tire markings as represented by different date configurations, ranging from the conventional month/day/year (12/05/07) to the DOT code’s four-digit week-year (2205). Effect of Text Format on Determining Tires’ Date of Manufacture, accepted by Annual Proceedings of 55th Human Factors and Ergonomics Society, found that when consumers chose to translate the different four-digit representations into a month and year, they consistently failed to understand that the first two digits represented the week of manufacture.

The DOT number, an alpha-numeric code found on the tire sidewall, has consistently confused consumers and tire professionals. The last four characters of the 11-character code contain the week and year the tire was made. For example, 0302 signifies that the tire was made during the third week of 2002. (Tires made prior to 2000 used a three-digit date configuration at the end of the DOT code.  In those cases, 039 signifies that the tire was manufactured during the third week of 1999 – or the 1989.)  No participant in Taylor and Wogalter’s study correctly identified examples such as 03/01 or 1102. They confused the first two digits with the month itself, for example, identifying “03” as March, instead of realizing that the third week of the year falls in January.

Taylor and Wogalter concluded:

“The method by which consumers are currently informed of the DOM [Date of Manufacture] of tires needs to be changed. A change is necessary because safety is involved, particularly the tire aging issue. One limiting factor to making the date more apparent and easier to use is that tire manufacturers are currently required to give the DOT number as specified by law. At the same time, manufacturers have a responsibility to ensure that consumers are provided adequate information for safe use of the product.”

Taylor said that one of the most striking observations was that the study participants came to the task ignorant of the DOT code itself.

“They don’t know what the different tire markings are,” Taylor said. “We asked if they ever looked at the DOT number and there were only a few people who said they had ever looked for it.”

Taylor and Wogalter are now working on a second study of consumers’ ability to correctly identify the date of a tire’s manufacture when it is embedded in the whole Tire Identification Number.

These results should surprise no one. Safety Research & Strategies has been studying and monitoring the tire age issue since 2003, and has presented its findings to NHTSA.

SRS pressed the agency to adopt a consumer-friendly date of manufacture for seven years. And the National Highway Traffic Safety Administration has promised to consider the issue, as part of a tire performance standard. As of this writing, it’s still in the making.

The Transportation Recall Enhancement Accountability and Documentation (TREAD) Act of 2000 required NHTSA to improve tire labeling to help consumers identify tires in the event of a recall. In 2004, the agency adopted a Final Rule that required the TIN be molded on the intended outboard side of the tire to give consumers easy physical access to the TIN. Manufacturers also had the option of molding a partial TIN, minus the date code, on the other side of the tire. NHTSA set the compliance date at September 1, 2009, and declined to change the date code to a readily recognized format using the month, day and year.

SRS first petitioned NHTSA to initiate rulemaking to require a non-coded date of manufacture molded into tire sidewalls in November 2004. The petition requested that tire labeling rulemaking be separated from the tire performance standards for expediency. We argued that changing the DOM from the obscure week and year representation to something that was immediately accessible to the average person wouldn’t conflict with other possible tire aging requirements. But, the agency decided to lump this petition into the tire performance rulemaking and indicated it would be considered at some future date.

In the meantime, NHTSA has identified a test protocol that has been generally accepted as a good artificial aging test followed by a roadwheel performance evaluation. And in 2008, the agency mentioned tire age as a hazard in a consumer advisory about tire care in the summer months.

While a performance standard would certainly ensure that tires were more robust, absent a change in the date code, consumers will still be in the dark about the age of their tires. That might please the Rubber Manufacturers Association, which has increasingly become isolated in its view that tire age doesn’t matter. But it won’t help consumers follow the recommendations of most automakers and some of the RMA’s own members to replace tires when they reach six to 10 years of age.

NHTSA might do well to take note of this latest study as it develops its proposal. Without a practical way for the average to consumer to easily read the date of manufacture, much of its excellent research and outreach will be wasted.

Tags: 
advocacy
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safety-research-strategies
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tire-aging
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