The National Highway Traffic Safety Administration (NHTSA) announced this week new research that reinforces its existing concerns about 15-passenger vans. As a result, NHTSA reissued its consumer advisory for users of 15-passenger vans for the third time in the past four years. In a new research report related to improper tire maintenance on 15-passenger vans, the NHTSA study found that 74 percent of all 15-passenger vans had significantly mis-inflated tires. By contrast, 39 percent of passenger cars were found with significant inflation problems. NHTSA research has consistently shown that improperly inflated tires can change handling characteristics, increasing the prospect of a rollover crash in 15-passenger vans. "The vans are convenient, but drivers and passengers have to use extra caution. The risks associated with 15-passenger vans can be minimized if users take some basic safety precautions", said Jeffrey Runge, M.D, NHTSA administrator. "Routinely checking the condition of the tires, including the tire pressure, should be at the top of the list".To reduce the risks associated with 15-passenger vans, NHTSA’s safety advisory recommends that drivers insist all occupants wear safety belts at all times; drivers of 15-passenger are trained and experienced; tires are checked at least once a week, using the manufacturer’s recommended pressure levels; and no loads are placed on the roof of the vehicle.Prior NHTSA research has shown that 15-passenger vans have a rollover risk that increases dramatically as the number of occupants increases from fewer than five to more than ten. In fact, 15-passenger vans (with 10 or more occupants) had a rollover rate in single vehicle crashes that is nearly three times the rate of those that were lightly loaded (with fewer than five occupants).Nearly 80 percent of those who died in 15-passenger van rollovers nationwide between 1990 and 2003 were not buckled up. Wearing safety belts dramatically increases the chances of survival during a rollover crash. In fatal, single-vehicle rollovers involving 15-passenger vans over the past decade, 91 percent of belted occupants survived.NHTSA is reissuing this advisory to specifically alert summertime users of 15-passenger vans.