Maryland highway officials opened a new Interstate 270 interchange Wednesday that will allow motorists to enter and leave the highway directly from Watkins Mill Road in Gaithersburg.

State officials have said the $124 million project, which spans 1.25 miles, will relieve traffic on surrounding roads. It also will provide better access to a highway that has one of the state’s largest jobs corridors and is a major commuting route connecting Maryland, the District and Northern Virginia.

Dave Abrams, spokesman for the Maryland State Highway Administration, said the $97.7 million that the state previously gave as the project’s cost did not include engineering, right-of-way acquisition or $4.9 million in unexpected costs.

Construction on the interchange north of one at Montgomery Village Avenue and Quince Orchard Road (Route 124) started in mid-2017. The project had been a top priority for Montgomery County officials who had said the Gaithersburg area’s growth over the past decade required it to have better access to I-270.

Maryland highway officials said the new bridge over I-270 also allows Watkins Mill to connect both sides of Gaithersburg and improves access to the Gaithersburg Medical Center, the MARC commuter rail station at Metropolitan Grove, and local neighborhoods and businesses.