The Transportation Department estimates that 32,788 people were killed on U.S. roads last year, a three percent drop from 2009. It's also the fewest number of deaths since 1949, when more than 30,000 people were killed.
A regional breakdown shows California, Arizona and Hawaii saw a decline of nearly 11 percent.
Officials credit more people wearing seat belts, better safety equipment in cars and effective campaigns to stop drunk driving.
The numbers are projections for 2010. The government expects to release final data on deaths and injuries, including specific state-by-state totals, later this year.
Traffic deaths typically decline during an economic downturn because many motorists cut back on discretionary travel. The number of deaths fell in the early 1980s and early 1990s, when the U.S. economy was struggling.
But people spent more time in their cars last year, making the estimates more noteworthy. The number of miles traveled by American drivers in 2010 grew by 20.5 billion, or 0.7 percent, compared with 2009, according to the Federal Highway Administration. The number of miles traveled increased slightly in 2009 after declines in the previous two years.
Separately, the rate of deaths per 100 million miles traveled is estimated to have hit a record low of 1.09 in 2010, the lowest since 1949. The previous record was in 2009, which had a rate of 1.13 deaths per 100 million miles traveled.
The Associated Press contributed to this report.