In August 1999, Bridgestone ∕ Firestone Inc. recalled 6.5 million tires in the wake of a number of tire-related rollover accidents in the Explorer SUV produced by Ford Motor Company. Although Firestone tires have an admirable overall quality record and the Explorer ranks second in its safety record among eight leading brands of SUV, 88 fatalities in the United States and as many as 50 fatalities overseas have been linked to the combination of Firestone tires (three particular brands) mounted on the Explorer. A review of the Firestone ∕ Ford debacle shows that both companies (as well as the National Highway Safety Administration) lacked the data to permit early recognition of this accident risk. (To this day, there is no way to "prove" the exact causes of the tire failures. Evidence and analysis of the safety risk is purely statistical.)
a. Ironically, the low overall rate of tire-related accidents made it more difficult to detect the particular Firestone ∕ Ford risk. Why would this be the case? Until 1999, Firestone relied exclusively on the low rate of tire claims under warranty to conclude that its tires were safe. Why might reliance on warranty data alone be a mistake?
b. The rate of tire failure is associated with multiple factors. The Explorer accidents with Firestone tires tended to occur at high speeds and at high temperatures. In addition, low tire pressures, recommended by Ford to increase ride comfort, tended to create more road friction and heat. (Carrying heavy loads has the same effect.) Precisely because the risk was associated with multiple, simultaneous factors, it was much more difficult to detect. Why would this be the case?
c. Ford believed that the major fault was with Firestone's tires. Firestone contended that its tires were absolutely safe under its recommended operating conditions, and that the Explorer's design and operation were the major culprits. What kind of information would one gather to assess these rival arguments? Explain.