Past Research

Tire Pressure Special Study (2001)4 This study used the 24 primary sampling units (PSUs) located
throughout the United States established by the National Automotive Sampling System
Crashworthiness Data System (NASS-CDS). Within these PSUs, drivers were sampled for observation at
gas stations from February 1, 2001, to February 14, 2001. According to the study, approximately 10
percent of the vehicles on the road in the United States were equipped with TPMS. A total of 11,530
vehicles were observed and the distribution of observed vehicle types (SUVs, vans, passenger cars, etc.)
was consistent with national estimates of vehicle registration. There were no restrictions on the model
years of included vehicles. The primary finding of this study was that 27 percent of passenger cars had
at least one tire that was underinflated by at least eight psi (which would correspond to 25%
underinflation for a tire with a common recommended pressure of 32 psi).
Tire Pressure Monitoring System Study (2009)5 This study also used the NASS-CDS infrastructure and
was specifically designed to analyze the effectiveness of TPMS. This study collected data from a limited
sample of 2,316 vehicles (data collection was halted before the planned sample size of 12,000
observations could be realized) from model years 1997 through 2003. The primary findings of this study
were that most of the surveyed vehicles with correct tire pressure were equipped with TPMS. This
study also found that 8.4 percent of observed vehicles with TPMS had at least one tire that was more
than 25-percent underinflated, while 9.9 percent of observed vehicles without TPMS had at least one
tire that exceeded the same level of underinflation. Most of the TPMS in this study (83%) were indirect
systems.