Traffic fatalities caused by alcohol-impaired drivers fell nationally in 2011 by 2.5 percent from a year earlier, a bigger decline than the percentage drop in overall traffic fatalities.

Despite that decline, the National Highway Traffic Safety Administration says, almost a third of the 32,367 highway fatalities in 2011 involved alcohol — including 393 during the last half of December alone.

“The holiday season can be an especially dangerous time on our nation’s roadways due to drunk drivers. That’s why law enforcement officers will be out in full force,” Transportation Secretary Ray LaHood said last week in announcing a holiday enforcement campaign with the Governors Highway Safety Association and Mothers Against Drunk Driving.

The number of roadway fatalities in 2011 was the lowest since 1949, and the fatality rate of 1.10 deaths per 100 million vehicle miles traveled was the lowest ever. Since 2005, the number of fatalities has declined by 26 percent.

LaHood credited NHTSA’s crash-ratings system, which tests crash worthiness and rollover safety, with making the vehicles on the roads today the safest ever. He also said aggressive enforcement of seat belt and drunken-driving laws have helped reduced fatalities.

“We’re still stuck with the fact that one in every three highway fatalities last year — 9,878 in total — was alcohol-related,” LaHood said in his blog.

NHTSA’s state-by-state breakdown released last week shows that impaired driving fatalities fell in 27 states, with Texas, New York, South Carolina and Tennessee registering the biggest declines. Colorado recorded the biggest increase in alcohol-impaired driving fatalities with 41, followed by 38 in Florida and 33 in New Jersey.

“Thanks to the hard work of safety advocates and law enforcement officers across the country, we’re seeing declines in drunk-driving deaths in many parts of the country — but there is still work to do,” NHTSA Administrator David Strickland said. “Ultimately, personal responsibility is critical to improving roadway safety, and we urge all motorists to be responsible this holiday season and never, ever drive drunk.”