Effects of Tire Pressure Monitoring Systems on Tire Pressures in Consumer Vehicles

In response to a federal mandate, all new light passenger vehicles in the United States will soon be required to include tire pressure monitoring systems (TPMSs) that alert drivers when one or more tires become 25% or more underinflated relative to the pressure level recommended by the vehicle manufacturer. Although the goal of TPMSs is to reduce the population of underinflated tires, their ultimate effect on tire pressure in consumer vehicles is unknown. Tire pressure and survey data were collected from approximately 1,200 vehicles that had just entered a rest area from an Interstate highway. Comparisons between vehicles with and without a TPMS were made from 864 vehicles in the full sample and from a subset of 123 target vehicles. The presence of TPMSs was generally associated with a small (0.7 to 1.5 psi) but significant decrease in the severity of tire underinflation. In addition, vehicles equipped with TPMSs were significantly less likely to have at least one tire that was 25% or more underinflated. The effect of TPMSs on tire pressure might have been larger had the systems been designed to activate at a less severe underinflation level. Less than 2% of survey respondents believed that TPMSs should have a trigger threshold as extreme as the currently mandated 25% threshold. Surveys also revealed that drivers without a TPMS do not report large differences in their tire maintenance behaviors relative to drivers with a TPMS and that more than 25% of drivers of vehicles with a TPMS are unaware that their vehicle is so equipped.