— The U.S. Department of Transportation will loan the North Carolina Turnpike Authority up to $501.5 million to help finance construction of the N.C. Highway 540 toll road in southern Wake County, U.S. Transportation Secretary Elaine Chao said Wednesday.

"This $501.5 million federal investment in transportation infrastructure in the Raleigh region will promote economic growth while enhancing mobility and reducing congestion for area residents and travelers," Chao said in a statement.

The state will use toll revenue from the highway to repay the loan.

Construction recently started on the southeastern part of N.C. 540 after years of delays prompted by environmental concerns.

The state Department of Transportation reached a settlement in August with several environmental groups to clear the way for the highway, known as the Triangle Expressway Southeast Extension.

Under the settlement, the DOT will take steps to reduce emissions from construction vehicles working on the project, will limit runoff to protect nearby streams, restore wildlife habitat and help Wake County preserve more open space.

The state has already awarded three contracts to build the six-lane highway from the N.C. Highway 55 Bypass in Apex to Pierce Olive Road, near Holly Springs, from there to east of U.S. Highway 401 and from there to Interstate 40.

The project is expected to open to traffic in 2023, officials said.

Work on the stretch between I-40 and U.S. Highway 264 in Knightdale won't start until 2029, according to DOT officials.