For the first time since 2005, traffic fatalities are on the rise in the U.S.

The National Highway Traffic Safety Administration (NHTSA) just released final data for 2012, which confirms the agency's earlier predictions of an increase.

According to NHTSA, highway deaths rose by 1,082, or 3.3 percent  to 33,561 in 2012, compared with the previous year. The agency says the majority of the increase in deaths (72 percent) occurred in the first quarter of the year and involved motorcyclists and nonoccupants.

NHTSA has a theory as to why that is. The first quarter of 2012 was the warmest on record, which "may explain some of the increase in fatalities in 2012, especially the number and pattern of those during January through March."

(graphic via NHTSA)

Some key statistics from 2012:

• Fatalities among pedestrians increased for the third consecutive year
• Motorcycle rider fatalities increased for the third consecutive year
• Deaths in crashes involving drunk drivers increased 4.6 percent
• Bicyclist deaths (called 'pedalcyclists' in NHTSA parlance) increased 6.5 percent

"As a public health and safety agency, any increase in the number of deaths is cause for concern," said NHTSA Administrator David L. Strickland. While we're seeing some unfortunate trends, we're also seeing progress in some parts of the country."

NHTSA's preliminary 2013 numbers indicate traffic fatalities are decreasing when compared to 2012.

Read the report here.