The U.S. 183 North expansion and toll project is no longer in the ditch.

The Texas Transportation Commission Thursday approved a deal with the Central Texas Regional Mobility to build the 9-mile, $500 million project between MoPac Boulevard and Texas 45 North. Under the deal, TxDOT would oversee the work, awarding a "design-build" contract next fallto build two toll lanes in each direction and, in several places, add a fourth free lane to either the southbound or northbound side of U.S. 183.

The road currently has several points where it narrows from four lanes a side to three.

The toll lanes would be in the highway’s broad center median, currently walled off by concrete barriers from the existing lanes. The project would include adding toll flyover bridges at the south end from MoPac’s newly opened toll lanes to the U.S. 183 toll lanes to come.

The project no longer includes one element: flyover bridges at the north end connecting U.S. 183 to RM 620 to the west. That lowered what had been a $650 million cost estimate to the $500 million now contemplated.

The project seemed to be in trouble this summer because of concerns over mixing TxDOT tax dollars with borrowed money from the mobility authority, particularly because of Texas Constitutional amendments passed in 2014 and 2015 that stipulate that some of TxDOT’s funds cannot be spent on toll projects. But TxDOT and the mobility authority worked out an unusual arrangement for the deal, one that passed muster with the commission.

TxDOT will provide $120 million, money that in theory will construct the added free lanes, along with bicycle and pedestrian improvements along the frontage roads. There would an added southbound lane between Lake Creek Parkway and near Texas 45 North, and from north of McNeil Road to Loop 1. Northbound, a lane would be added between Braker Lane and Spicewood Springs Road.

The mobility authority would kick in $380 million in borrowed money. About $240 million would come from a bond sale, authority executive director Mike Heiligenstein said. And the agency hopes to get another $140 million from a U.S. Department of Transportation loan program, one that the agency has borrowed from on previous toll projects.

If the timetable holds up, construction likely would begin in early 2019.