It’s got a clunky name, but has a major aim: the $1.6 billion Regional Connector transit project will bring four different rail lines together in downtown Los Angeles, causing street traffic tie-ups while work proceeds but eliminating many of the transfers that frustrate passengers once completed.

The project’s thousand-ton tunnel boring machine was lowered ceremoniously underground Wednesday in preparation for major construction that begins next year.

The machine, which is 21.5 feet in diameter, gets assembled underground before it begins digging twin, 1.1-mile tunnels under downtown. Named Angeli after an old mining tradition when the equipment was called by a female moniker, the boring machine will create the path for a rail line to connect three currently disconnected light rail lines.

When it opens in 2021, passengers will have a one-seat ride from Long Beach to Azusa along the Blue and Gold Lines and from East L.A. to Santa Monica along the Gold Eastside Extension and Expo Lines. There won't be a need for transfers between Union Station and 7th and Metro station. Metro estimates the connector will reduce travel times by as much as 20 minutes.

The Regional Connector will span 1.9 miles through downtown from 7th and Metro station to 2nd and Hope Street, adding three new stations.

“This is a major milestone toward the completion of a vital project that truly connects the region by providing a one-seat ride to downtown Los Angeles for users of the Blue, Gold and Expo lines,” said John Fasana, Metro board chair and Duarte City Council member.

Tunnel-digging begins in January and will advance at a rate of about 60 feet a day.

The project has already hit cost overruns and delays due to unexpected underground utility lines discovered during early phases of construction. Because downtown L.A. is one of the oldest and densest areas of the city, many existing utilities have never been mapped.

Metro relocated the utility lines and extended its timeline for the project at a cost of an extra $130 million. The anticipated opening date for the line has been shifted from 2020 to 2021.

Street closures around Little Tokyo have ended as construction moves underground with tunneling, but several streets will remain closed around the construction of the future 2nd Street and Hope Street station.