The rollover risk of 15 passenger vans is exceptionally high and has contributed to hundreds of serious injuries and deaths. On June 1, 2004, Dr. Jeffrey Runge, head of the U.S. Department of Transportation's National Highway Traffic Safety Administration (NHTSA), issued a warning to users of 15-passenger vans because of an increased rollover risk under certain conditions. Similar warnings were issued in 2001 and 2002. When filled with passengers, or driven above 50 miles per hour, the vehicles become substantially more unstable than SUVs or pickup trucks. Large vans are five times more likely to roll over when filled than when only the driver is in the vehicle. The greater passenger weight in a fully loaded van raises the van’s center of gravity and shifts it toward the rear. As a result, the van has less resistance to rolling over in an accident or emergency situation. Placing any load on the roof also raises the center of gravity and increases the likelihood of a rollover. The NHTSA found that eighty percent of those who died in 15-passenger van rollovers nationwide in the year 2000 were not wearing their seatbelts.