The head of the U.S. Department of Transportation (DOT), Secretary Ray LaHood, announced he is stepping down after serving for four years in President Obama’s cabinet. The Secretary sent a letter via email to DOT employees across the country, thanking the DOT’s staff for its hard work and mentioning specific accomplishments.

“I have let President Obama know that I will not serve a second term as Secretary of the U.S. Department of Transportation,” LaHood said in his farewell letter. “It has been an honor and a privilege to lead the Department, and I am grateful to President Obama for giving me such an extraordinary opportunity. I plan to stay on until my successor is confirmed to ensure a smooth transition for the Department and all the important work we still have to do.”

LaHood noted the role the federal agency has played in efforts to reduce incidents of distracted driving and its involvement in crafting new fuel economy standards. He also said the agency had been recognized as the “most improved agency” in the federal government in the 2012 “Best Places to Work” rankings published by the Partnership of Public Service.