Transportation Secretary Ray LaHood, whose job status had remained unclear since President Barack Obama's re-election, announced he will not stay on board for a second term.

For months, transportation officials and stakeholders had been guessing whether LaHood would remain in office. His announcement today will likely further the speculation over who will serve as his successor.

LaHood made the announcement to U.S. Department of Transportation employees this morning. He said he will remain in his position until a successor is confirmed.

After serving for all four years of the president's first term, LaHood departs at a key time of transition in the transportation community. During his tenure, Congress spent years debating a long-term highway bill that was often the subject of bitter partisan debate. It ultimately passed a two-year bill last year. His departure ensures that a new transportation secretary will be in office when Congress begins planning out the successor to that legislation.

As transportation secretary, LaHood's signature issue was the reduction of distracted driving, and he addressed it as often as he could. He also presided over the department at a time when it helped oversee $48 billion in infrastructure investment associated with the 2009 stimulus bill.

His tenure in office also coincided with the development of the innovative TIGER grants, which have awarded $2.7 billion in several rounds of funding to jurisdictions that had to compete for the projects. Many in the transportation community viewed TIGER as an innovative program that could serve as a model for other transportation grants.

"Under his leadership, we have made significant investments in our passenger rail system and laid the groundwork for the high-speed rail network of the future," President Obama said in a statement. "And every American who travels by air, rail or highway can thank Ray for his commitment to making our entire transportation system safer and stronger."

Yet LaHood's tenure was also marked by some frustrations. While President Obama made high-speed rail a priority, Congress has worked to cut off that funding, and LaHood sometimes faced criticism of the program, especially after three Republican governors' rejected high-speed rail money.

His time in office was also marked by frustration with Congress over its inability to pass a long-term transportation bill. While Congress last year did pass a highway and transit bill, known as MAP-21, that offered level funding, it failed to make the major changes necessary to transportation policy that would ensure transportation funds remains sustainable in the long term.

Famously in 2009, LaHood endorsed the idea of exploring the idea of moving towards a vehicle miles traveled fee, which would provide a more stable funding stream than the gas tax and is an idea endorsed by many in the transportation community. The White House quickly backed away from that suggestion.

 "Now is not the time to let up - we still have a number of critical safety goals to accomplish and still more work to do on the implementation of MAP-21," LaHood said in his email to DOT employees.