The number of traffic fatalities continued its welcomed downward trajectory last year, falling 3% to its lowest levels since 1949, and a 25 percent drop from 2005, according to U.S. Department of Transportation estimates. Preliminary figures show that 32,788 people died in traffic accidents last year, down from the 33,808 killed the previous year and significantly below the 43,510 people killed only six years ago, according to the DOT's National Highway Traffic Safety Administration. Experts attribute the change to a variety of reasons, including changes to cars -- such as vehicle rollover protection -- and programs to change driver behavior -- such as campaigns addressing drunk driving, distracted driving and seat belt use. Laws aimed at young people also likely have had an impact, notably older minimum drinking ages and graduated drivers' licenses. But the rise and decline of the grim number has numerous peaks and dips, influenced by direct changes such as the national speed limit and indirect causes such as recessions.