NHTSA Report on Tire Safety:

Section of Report from The National Highway Traffic Administration (NHTSA), Department of Transportation (DOT)

Topic on Importance of Tire Pressure in Relation to

a.    Vehicle Safety
b.    Tire Tread Life
c.    Fuel Economy

III.  Safety Problem

Many vehicles have significantly under-inflated tires, primarily because drivers infrequently check their vehicles' tire pressure. Other contributing factors are the difficulty of visually detecting when a tire is significantly under-inflated and the loss of tire pressure due to natural leakage and seasonal climatic changes.

A. Infrequent Driver Monitoring of Tire Pressure

Surveys have shown that most drivers check the inflation pressure in their vehicles' tires infrequently. For example, in September 2000, the Bureau of Transportation Statistics (BTS) conducted an omnibus survey for NHTSA. One of the questions posed was: "How often do you, or the person who checks your tires, check the air pressure in your tires?" The answers indicated that 29 percent of the respondents stated that they check the air pressure in their tires monthly; another 29 percent stated that they check the air pressure only when one or more of their vehicle's tires appears under-inflated; 19 percent stated that they only have the air pressure checked when the vehicle is serviced; 5 percent stated that they only check the air pressure before taking their vehicle on a long trip; and 17 percent stated that they check the air pressure on some other occasion. Thus, 71 percent of the respondents stated that they check the air pressure in the vehicles' tires less than once a month.⁽¹⁷⁾

In addition, NHTSA's National Center for Statistics and Analysis (NCSA) conducted a survey in February 2001. The survey was designed to assess the extent to which passenger vehicle drivers are aware of the recommended air pressure for their vehicles' tires, if drivers monitor air pressure, and to what extent actual tire pressure differs from placard pressure.

Data was collected through the infrastructure of the National Accident Sampling System - Crashworthiness Data System (NASS-CDS). The NASS-CDS consists of 24 Primary Sampling Units (PSUs) located across the country. Within each PSU, a random selection of zip codes was obtained from a list of eligible zip codes. Within each zip code, a random selection of two gas stations was obtained.

A total of 11,530 vehicles were inspected at these gas stations. This total comprised 6,442 passenger cars, 1,874 sports utility vehicles (SUVs), 1,376 vans, and 1,838 pick-up trucks. For analytical purposes, the data were divided into three categories: (1) passenger cars; (2) pick-up trucks, SUVs, and vans with P-metric tires; and (3) pick-up trucks, SUVs, and vans with either light truck (LT) or flotation tires. 

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