Four vehicle accidents between February and May of 2014 took 12 lives and injured 42 more. While the specifics of the accidents varied, all four were due to tread separations on tires. Later that year the National Transportation Safety Board (NTSB) hosted a Passenger Vehicle Tire Safety Symposium to address areas of concern regarding passenger vehicle safety due to tire issues. A special investigation report, which was adopted October 27, 2015, provides a summary of the issues and industry-wide recommendations to improve passenger vehicle safety.
There are multiple issues causing safety concerns with tires, and multiple recommendations to mitigate these safety risks. When dealing with a complex issue such as this, it can help to visually diagram the cause-and-effect relationships. We can do this in a Cause Map, or visual root cause analysis. This analysis begins with an impact to the organization’s goals. According to the NTSB report, tire-related accidents cause more than 500 deaths and 19,000 injuries every year in the US. Customer service (customers being members of the public who purchase and/or use tires) is impacted due to a lack of understanding of tire safety. The regulatory goal is impacted due to a lack of tire registration, and the production goal is impacted due to a low recall completion rate. Lastly, the property goal is impacted due to tires that are improperly maintained.
Cause-and-effect relationships are developed by beginning with an impacted goal (in this case, the deaths and injuries) and asking “why” questions. In this case, the deaths and injuries are due to tire-related accidents, of which there are about 33,000 every year in the US. Tire-related accidents includes accidents that are due to tire issues (such as tread separation) caused by improper maintenance or an unrepaired manufacturing issue with a tire (specifically those resulting in a tire recall). While the NTSB is recommending the promotion of technology that may reduce the risk of tire-related accidents, they also made recommendations that can reduce the risk of these accidents in the near term.
From 2009-2013, there were 3.2 million tires recalled in 55 safety campaigns. However, 56% of recalled tires remain in use, because of very low recall work completion rates. In a typical tire recall, only about 20% of recalled tires are returned to the manufacturer. (In comparison, about 78% of recalled cars are repaired.) Many tires aren’t registered, and if they aren’t, it’s difficult to reach owners when there are recalls. Independent dealers and distributors, which sell 92% of tires in the US, aren’t required to register tires. While it is possible for consumers to look up their own tires to determine if they’ve been recalled, it’s difficult. The full tire identification number may not be printed in an accessible location, and the National Highway Traffic Safety Administration (NHTSA) website for tire recalls was found to be confusing.
The NTSB has recommended that tire manufacturers include the full tire identification number on both the inboard and outboard side walls of each tire so it can be more easily found by consumers. The NTSB has also recommended that the NHTSA, with the cooperation of the tire industry and Congress, if necessary, improve its recall site to allow search by identification number or brand and model, and improve registration requirements and the recall process.
Regarding improper maintenance, the report found that 23% of tire-related crashes involved tire aging and that 50% of drivers use the wrong tire inflation pressure, 69% have an underinflated tire, 63% don’t rotate their tires, and 12% have at least one bald tire. The report found that consumers have an Inadequate understanding of tire aging and service life and recommends developing test and best practices related to tire aging, and developing better guidance for consumers related to tire aging, maintenance and service life.
The NTSB has issued its own Safety Alert for Drivers, which includes the following guidance:
– Register new tires with the manufacturer
– Check your tire pressure at least once a month
– Inflate your tires to the pressures indicated in your vehicle owner’s manual (not on the tire sidewall)
– When checking tire pressure, look for signs of damage
– Keep your spare tire properly inflated and check it monthly for problems
– Rotate, balance and align your tires in accordance with your vehicle owner’s manual
– If you hear an unusual sound coming from a tire, slow down and have your tires checked immediately
To view the Cause Map, including impacted goals and recommendations, click on “Download PDF” above. Or, click here to read the NTSB’s executive summary.