BOSTON – Next month’s expansion of the Silver Line into Chelsea will plug the city into Boston’s two commuter rail hubs and make it a prime location for transit-oriented development, Transportation Secretary Stephanie Pollack said Monday.

 “Chelsea will actually be one of the only places in close proximity to Boston where folks can get to both South Station and North Station easily,” Pollack told the MBTA’s Fiscal and Management Control Board.

 The city has a commuter rail station linked to North Station and the Silver Line will connect to South Station. North and South stations are not connected.

 Dubbed Silver Line 3, or SL3, the bus rapid transit is expected to carry nearly 9,000 passengers per day, making a total of seven stops, linking the South Boston Seaport to Airport Station in East Boston and four new bus stations in Chelsea.

 Construction on the $56.7 million project began in 2015 and was primarily funded by the MBTA. The Massachusetts Department of Transportation contributed $7.6 million and MassDOT’s Highway Division managed the construction. The construction contract was awarded to McCourt Construction Company in 2014.

 Buses will run within about 10 minutes during rush hour and 12 to 15 minutes in off-peak travel times, and fares will be the same as the subway, said Jess Casey, the MBTA’s deputy chief operating officer for service planning and strategy.

 On much of the five-mile route, the bus will be unimpeded by traffic, traveling in its own dedicated corridor in nearly all of Chelsea.

 The Chelsea Street Bridge – a drawbridge linking Chelsea and East Boston – will create a wrinkle in routes and scheduling, Casey told the MBTA’s Fiscal and Management Control Board, calling it the “elephant in the room.”

The Silver Line will travel in traffic across the bridge, which takes a total of 20 minutes to raise and lower for ships, according to Casey, who said the T is working with the U.S. Coast Guard on protocols to alert T dispatchers when the bridge is opening or closing so they can divert bus traffic around it.

The vertical-lift drawbridge was built over the Chelsea Creek in 2012, replacing an older span, and last summer the Massachusetts Department of Transportation announced new dynamic road signs to alert travelers when the bridge is up or down.

 The Silver Line extension will be the first new introduction of service on the T in more than a decade, since the Greenbush commuter rail commuter-rail line, according to the T. The new service will start on Saturday April 21, and the T plans a ribbon cutting the following week, Casey said.

 In 2014, the T completed the construction of Assembly Station on the Orange Line, the first new subway station in 27 years. The MBTA and MassDOT are also working on the more ambitious and expensive Green Line Extension to extend trolley service from East Cambridge through Somerville to Medford.