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Many U.S. Passenger Cars Are Driven on "Bald" Tires, NHTSA Research Shows

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American Government

Many U.S. Passenger Cars Are Driven on "Bald" Tires, NHTSA Research Shows

NHTSA
November 30, 2001

NHTSA 61-01
Friday, November 30, 2001
Contact: Elly Martin
Telephone: (202) 366-9550

U.S. Transportation Secretary Mineta Announces Launch Of Major Nationwide Campaign to Promote Tire Safety

Responding to new studies showing that a significant number of American motorists are driving on bald tires and that many gas stations that provide air pumps fail to provide accurate tire pressure gauges, U.S. Transportation Secretary Norman Y. Mineta today urged motorists to closely monitor their tires.

"It is extremely important to motorists' safety that they ensure their tires have ample tread and are properly inflated," Secretary Mineta said. "Motorists who drive on tires that are bald or substantially under-inflated risk injuries or fatalities."

To better protect motorists, the U.S. Department of Transportation's National Highway Traffic Safety Administration (NHTSA) is launching a new tire safety campaign based on the theme: "Tire Safety: Everything Rides on It." The purpose of the campaign, to involve radio public service announcements, print ads and brochures, is to stress the importance of proper tire inflation and vehicle load limits. The campaign is also designed to encourage motorists to check their tires monthly, as well as prior to a long trip, to be sure they have adequate tread.

"It is vitally important that motorists monitor tread depth to guard against tire failure and replace unsafe tires. Checking tires is a crucial element in regular vehicle maintenance," said Dr. Jeffrey W. Runge, NHTSA's Administrator.

According to a major survey conducted by NHTSA, fully 9 percent of passenger cars on U.S. roadways are driven with at least one bald tire.

Moreover, another major NHTSA study found that 14 percent of gas stations are either not equipped with air pumps or have malfunctioning pumps. Also, only 49 percent of gas stations that are equipped with air pumps provide tire pressure gauges, which are critical to determining if the correct amount of air has been delivered to tires. However, for a nominal price, motorists can purchase a tire pressure gauge.

To help vehicle owners better monitor the air pressure in their tires, NHTSA in July proposed a new federal motor vehicle safety standard that would require the installation of tire pressure monitoring systems in new passenger cars and light trucks. The new system would warn the driver when a vehicle has a significantly under-inflated tire.

One alternative would require that the driver be warned when the pressure in one or more tires, up to a total of four tires, has fallen to 20 percent or more below the vehicle manufacturer's recommended cold inflation pressure for the vehicle's tires, or a minimum level of pressure to be specified in the new standard, whichever is higher.

The other alternative would require that the driver be warned when tire pressure in one or more tires, up to a total of three tires, has fallen to 25 percent or more below the vehicle manufacturer's recommended cold inflation pressure for the vehicle's tires, or a minimum level of pressure to be specified in the new standard, whichever is higher. Only one version will be in the final rule.

Tire tread provides the gripping action and traction that prevent a vehicle from slipping and sliding, especially when the road is wet or icy. In general, tires are not safe and should be replaced when the tread is worn down to 1/16th of an inch. Tires have built-in treadwear indicators that let a motorist know when they should be replaced. These indicators are raised sections spaced intermittently in the bottom of the tread grooves. When they appear "even" with the outside of the tread, it's time for tire replacement.

Another method of checking tire tread involves use of a Lincoln penny. The motorist should place the penny upside down within the tread. If the top of Lincoln's head is visible, the tire needs to be replaced.

NHTSA's new tire safety campaign will involve three new public service announcements to run on 2,000 radio stations throughout the country; print ads in newspapers and magazines; and more than 500,000 flyers to be given free-of-charge to consumers through tire retail outlets and other channels. Some of the materials will be in Spanish as well as English. Consumers can obtain tire safety information from NHTSA by calling the agency's Hotline: 888-327-4236. NHTSA's new flyer and brochure, both titled "Tire Safety: Everything Rides on It," can be viewed on the agency's web site, www.nhtsa.dot.gov.

Printed materials used as part of the campaign will be distributed by NHTSA as well as Championship Auto Racing Teams, Inc. (CART), the Rubber Manufacturers Association (RMA), and the Tire Association of North America (TANA).

NHTSA's analysis of tire wear was based on information gathered on 6,240 passenger cars during a 14-day period earlier this year. Information for the survey was collected with the cooperation of motorists who visited gas stations for refueling at 300 sites in urban, suburban and rural settings located throughout the country.

To conduct its survey on air pumps at gas stations, NHTSA collected information at the same 300 stations where data were gathered on tire wear. Just 139 of those 300 stations were found to have working air pumps, along with tire pressure gauges. These stations were later revisited to evaluate the accuracy of their gauges.

Key findings of the NHTSA study on tire tread include these estimates:

  • Nine percent of passenger cars are being driven on at least one "bald" tire. (For purposes of this survey, a tire was considered bald if it had 1/16th of an inch or less of tread depth.)
  • Bald tires are between 1.5 and 1.8 times more likely to be underinflated than are tires with deeper tread, depending on tire location. Key findings of the NHTSA study on gas station air pumps include these estimates:
  • Well over 90 percent of U.S. gas stations are equipped with air pumps. However, nearly 10 percent of these pumps are out-of-order.
  • Fewer than half of the pump-equipped gas stations also provide a tire pressure gauge for customer use.
  • Nearly 20 percent of the stations providing customers with tire pressure gauges on their air pumps use gauges that over-report the pressure present in a tire by at least 4 psi (pounds per square inch) or more. (This means that motorists who use such gauges in the belief that they are inflating their tires to the recommended pressure would, in fact, be under-inflating them by 4 psi or more.)
  • At the pressure levels that are typical for most passenger cars or SUVs, nearly 10 percent of gas station air pump gauges over-report by 6 psi or more.

    A NHTSA research survey of U.S. passenger vehicles that was released in August found that 27 percent of passenger cars on U.S. roadways are driven with one or more substantially under-inflated tires. In addition, the survey found that 33 percent of light trucks (including sport utility vehicles, vans and pickup trucks) are driven with one or more substantially under-inflated tires.

    A radial tire can lose much of its air pressure and still appear to be fully inflated. Operating a vehicle with substantially under-inflated tires can result in a tire failure, such as instances of tire separation and blowouts, with the potential for a loss of control of the vehicle. Under-inflated tires also shorten tire life and increase fuel consumption.

    Tires should be inflated in accord with the vehicle manufacturer's recommendations. These can be found in the owner's manual or on a placard, which is often located in the glove compartment or on the driver's doorjamb. Motorists should not rely on visual tire inspections to determine whether a tire is properly inflated but should use a tire pressure gauge to do so.

    Like tires that are under-inflated, bald tires also pose risks to motorists. A tire with insufficient tread can cause a driver to lose traction, especially under wet conditions. In addition, bald tires are more prone to damage caused by road debris.

    NHTSA's National Center for Statistics and Analysis conducted the two new studies. Statistics from the studies are contained in research notes on the agency's Website at: www.nhtsa.dot.gov/people/ncsa.

    --------------------------------------------------------------------------------

    Research Note

    Tire Pressure Special Study Tread Depth Analysis

    Air Pumps at U.S. Gas Stations: Major Findings Regarding Availability, Reliability and Fees

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