12 & 15 passenger vans tire pressure study : preliminary results

Thiriez, Kristin K.; Ferguson, Eric; Subramanian, Rajesh · 2005 · ROSA P / United States. Department of Transportation. National Highway Traffic Safety Administration

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Summary

This research note presents preliminary findings from the National Highway Traffic Safety Administration’s (NHTSA) Van Tire Pressure Study (VTPS), conducted to assess the extent of tire underinflation and condition in 12- and 15-passenger vans. The study was motivated by public and regulatory concerns regarding the safety of these vehicles, particularly their rollover risk, following the introduction of the Passenger Van Safety Act of 2003 and recommendations from the National Transportation Safety Board. As part of NHTSA’s 15-Passenger Van Action Plan, the agency utilized the infrastructure of the National Automotive Sampling System to determine if poor tire maintenance contributed to safety hazards in these high-occupancy vehicles. The VTPS employed a convenience sample design, collecting data from 1,242 vehicle inspections across 16 locations in the United States during spring and early summer 2004. The sample included 937 15-passenger vans, along with 12-, 14-passenger, and cargo vans with similar body styles. Vehicles were selected from organizations such as colleges, churches, camps, and transportation services, focusing on fleets that transport children and young adults. Researchers measured tire pressure, tread depth, and sidewall temperature, comparing actual pressures to manufacturer-recommended placard values. To avoid bias, participants were not informed that tire pressure was the specific focus of the inspection. Additionally, nine anecdotal interviews were conducted with fleet managers to assess maintenance practices and safety awareness. The results revealed significantly higher rates of tire misinflation in vans compared to passenger cars. Fifty-six percent of all vans had at least one tire underinflated by 25% or more relative to the recommended pressure, more than double the rate found in passenger cars in previous studies. Furthermore, 22% of vans had at least one tire overinflated by 25% or more, often because operators incorrectly used the maximum pressure listed on the tire sidewall rather than the vehicle placard. Rear tires were disproportionately affected, with 50% showing significant underinflation compared to 8–9% of front tires. The average underinflation for vans was 29% below recommended pressure. Regarding tire condition, 6% of 15-passenger vans had at least one bald tire (2/32nds of an inch or less), and 4% showed visible signs of aging or damage. The study concludes that poor tire maintenance in 12- and 15-passenger vans poses a substantial safety risk, particularly given that these vehicles often carry groups of children and are driven by inexperienced operators. The high prevalence of underinflation and overinflation suggests a critical need for improved driver training and public awareness regarding proper tire maintenance. NHTSA recommends countermeasures such as integrating Tire Pressure Monitoring Systems (TPMS) into these vans, equipping vehicles with tire gauges, and enforcing monthly cold tire checks. The findings underscore that regardless of technological interventions, educating operators on using vehicle placards rather than tire sidewall markings is essential for improving van safety.

Key finding

56% of 12- and 15-passenger vans had at least one tire underinflated by 25% or more compared to manufacturer recommendations.

Methodology

field_study

Sample size: 1242

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

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