Washington (CNN) -- The U.S. government reports a 9% increase in motor vehicle traffic fatalities for the first half of 2012, the largest jump during the first six months of any previous year since data was first collected in 1975.
A statistical projection from January through June estimates 16,290 people died in vehicular crashes this year, according to the National Highway Traffic Safety Administration.
The previous highest increase during the first half of the year was 6.4% in 1979.
In releasing the report, the administration said, "While it is too soon to speculate on the contributing factors or potential implications of any increase on our roadways, it should be noted that the historic downward trend in traffic fatalities in the past several years... means any comparison will be to an unprecedented low baseline figure."
The government pointed out fatalities during the first half of the year have declined by about 27% from the recent high in 2006 (20,500 fatalities) to the first half of 2011 (14,950 fatalities.)
The American Automobile Association called this year's numbers "alarming."
"This news is very disturbing," Lon Anderson, spokesman for AAA Mid-Atlantic, said in a statement. "We have worked decades to reduce fatalities in America... but this is a serious shot across the bow, a warning that as we drive more, our roads may not be as safe as we thought they were."
Anderson cites an improved economy with more cars, trucks and traffic on the roads as one explanation for the rise.
"Another likely contributing factor to these fatalities is the continued deterioration of highways and deferral of needed maintenance and improvements by federal and state governments," he said.
Data from the Federal Highway Administration showed vehicle miles traveled in the first six months of 2012 increased by 15.6 billion miles, a 1.1% increase from 2011.