The National Highway Traffic Safety Administration released a new analysis showing that highway deaths fell to 32,367 in 2011, marking the lowest level since 1949 and a 1.9% decrease from the previous year. Large-truck fatalities, however, rose, with the number of large-truck occupants killed jumping by 20%.

The updated 2011 data show the historic downward trend in overall fatalities in recent years continued through last year and represent a 26% decline in traffic fatalities overall since 2005.

However, fatalities increased by 20% among large truck occupants, rising from 530 in 2010 to 635 in 2011. Injuries are up as well, by 15%. Yet the number of other vehicle occupants killed in large-truck crashes fell by 3.6%, resulting in an overall increase of only 1.9% in people killed in large-truck crashes.

NHTSA says it is working with the Federal Motor Carrier Safety Administration to gather more detailed information on the large truck occupant crashes to better understand the increase in fatalities in 2011.

Speculation as to the cause of the jump in track crashes has included the fact that more trucks are returning to the road as the economy improves, as well as higher speed limits in some parts of the country.

The highway bill passed earlier this year, MAP-21, directs NHTSA to study how well large trucks protect their occupants in crashes, a provision pushed by both the American Trucking Associations and the Owner-Operator Independent Drivers Association.

The number of people killed in distraction-affected crashes rose to 3,331 in 2011 from 3,267 in 2010, an increase of 1.9%. NHTSA believes this increase can be attributed in part to increased awareness and reporting.

An estimated 387,000 people were injured in distraction-affected crashes, a 7% decline from the estimated 416,000 people injured in such crashes in 2010. Thirty-six states experienced reductions in overall traffic fatalities, led by Connecticut with 100 fewer fatalities.

Read NHTSA's report