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 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 o