WASHINGTON -- Transportation Secretary Ray LaHood, who lifted the profile of distracted driving as a national safety concern, is stepping down, presenting President Barack Obama with another Cabinet vacancy at the start of his second term.

The former congressman from Illinois and one of only two Republicans who served in Obama's Cabinet, LaHood worked for more safety in the air and on the ground and pushed for improvements of roads and bridges. Under his watch, the department demanded tougher fuel efficiency requirements for automakers and took steps to address airline pilot fatigue.

Obama, who at one point served with LaHood in the Illinois congressional delegation, said they were "drawn together by a shared belief that those of us in public service owe an allegiance not to party or faction, but to the people we were elected to represent. And Ray has never wavered in that belief."

LaHood, 67, said in an interview with The Associated Press that he told Obama a week after the November election that he needed to move on. But he also said he was still "conflicted" by his decision because he liked working for the president and considered it the "best job I've ever had in public service."

He said he plans to remain at the department until his successor is confirmed by the Senate, which he expects in about two months. The only other Republican who was in Obama's first-term Cabinet was Defense Secretary Robert Gates, who stepped aside and was replaced by Democrat Leon Panetta earlier.

LaHood, who was once considered likely to run for governor in his home state, said he would not seek public office and indicated he didn't have any specific plans.

"I have had a good run. I'm one of these people who believe that you should go out while they're applauding," he said. LaHood said he was content to watch from the sidelines as his oldest son, Darin, serves in the Illinois state senate.

His move continues an exodus that will give Obama's team a new look in his second term. Secretary of State Hillary Rodham Clinton, Panetta and Treasury Secretary Timothy Geithner are departing and in addition to LaHood, the heads of the Interior and Labor departments also have announced their resignations. Obama has nominated former Nebraska Sen. Chuck Hagel, a Republican, to serve as defense secretary to succeed Panetta.

Possible replacements for LaHood include Los Angeles Mayor Antonio Villaraigosa, who has pushed for increased rail service in Los Angeles and served as chairman of last year's Democratic National Convention, and Debbie Hersman, the chairman of the National Transportation Safety Board. The name of former Rep. Jim Oberstar of Minnesota, who led the House Transportation and Infrastructure Committee, has also been mentioned.

LaHood served seven terms in Congress representing a central Illinois district that includes his hometown of Peoria, Ill., before he was chosen by Obama for the post. He traveled widely, visiting 49 states, 210 cities and 18 countries promoting Obama's agenda. He made trips that allowed him to ride some of the world's fastest trains and inspect the latest vehicles at auto shows.

In Washington, he would occasionally don a bicycle helmet and pedal around the District to promote bike lanes.

At the start of the new administration, LaHood spearheaded efforts to stimulate the economy through transportation construction projects and promoted the administration's vision of a nation connected by high-speed trains. But the high-speed rail program, which was supposed to be one of the president's signature projects, has been on life-support since Republicans regained control of the House in the 2010 election.

LaHood was the administration's chief advocate for greater spending to repair and improve the nation's aging transportation network. But his impact was limited by the administration's refusal to back an increase in the federal gas tax or an alternative long-term funding scheme. Congress last year agreed on a plan that delays for two years decisions on how the nation will pay for highway and transit programs while giving states more flexibility in how they spend federal money.

Perhaps LaHood's most passionate work involved distracted driving, which he called a "national epidemic." He launched a national media campaign to end texting and cellphone use by drivers, an awareness campaign that drew comparisons to efforts to promote seat belt use more than a generation ago. He buttonholed auto executives to help reduce driver distraction and would even yell at other drivers on occasion to put down their cellphones.

"Every time someone takes their focus off the road – even if it's just for a moment – they put their lives and the lives of others in danger," he said in 2010.

During his tenure he slapped Toyota Motor Co. with record fines for delaying safety recalls and failing to promptly report problems to federal regulators. And he recently ordered United Airlines to ground its Boeing 787 Dreamliner following mishaps with the aircraft's batteries.

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Associated Press writer Joan Lowy contributed to this report.

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Follow Ken Thomas at: http://twitter.com/AP_Ken_Thomas

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