Trump to nominate Elaine Chao for transportation post: source

President-elect Donald Trump plans to nominate former Labor Secretary Elaine Chao to head the Transportation Department, a source with knowledge of the decision said on Tuesday.

The source, who requested anonymity, confirmed the pick to Reuters. Chao, the wife of Republican Senate Majority Leader Mitch McConnell, served as labor secretary under President George W. Bush and was the first Asian-American woman to hold a Cabinet position. The formal announcement was expected Tuesday afternoon.

Although Trump spoke on the campaign trail about wanting to "drain the swamp" in Washington, more than half of Trump's nine key appointments so far have been accomplished Washington insiders, such as Chao.

Chao will face a number of big decisions at the agency that overseas the nation's vehicles, airplanes, railroads, pipelines, ports and highways - including how to proceed on the use of self-driving cars on U.S. roads, the use of unmanned aerial vehicles, or drones, and whether U.S. fuel efficiency standards should be revised.

She may also take a leading role in Trump's plans to rebuild U.S. infrastructure. Trump has called for $1 trillion in infrastructure spending over 10 years to rebuild airports, bridges and other projects, but it is unclear how much of the funding would come from the federal budget.

Chao is a former U.S. deputy transportation secretary and sits on the board of Wells Fargo & Co .

(Reporting by David Shepardson; Writing by Doina Chiacu; Editing by Eric Walsh and Jonathan Oatis)