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.