Silver Line-style bus could serve Sullivan Square, North Station and Kendall

Silver Line bus at the Chelsea stop in April 2018. Lane Turner/Globe Staff/File/Globe Staff

One year after the state extended the Silver Line to Chelsea, officials are now planning additional new service into Cambridge, Charlestown, and beyond.

A coalition of state, municipal, and regional agencies this week said they were planning to extend the route of the Silver Line from Chelsea to Sullivan Square and beyond, along two courses: one would go to North Station in Boston; the second would course through Somerville, ending at Kendall Square.

While the new service might not be in a Silver Line bus, the routes would likely run within their own roads for much of the trip, similar to the dedicated busway in Chelsea, before moving onto bus-only lanes on local streets to complete the trip. And both would have stops at the new Encore Boston Harbor casino in Everett, scheduled to open this spring.

There is no set timeline for when the service would come online, however; officials said they would begin the planning and engineering process in the coming years.

The proposed new service is the result of a study ordered up to assess the traffic impacts from the Encore casino on the lower Mystic River area, which is also seeing other big new projects that are expected to add population.

Transportation Secretary Stephanie Pollack said officials were “looking at the issue from a much broader lens than, ‘is the casino going to create traffic jams?’”

Sullivan Square — one of the most maddening sites for both motorists and pedestrians in Boston — is already slated for a huge makeover by the city, as is Rutherford Avenue, the main road between the square and downtown Boston.

The new study took a longer view, determining how to manage all the new growth expected by 2040.

The report also recommended building a footbridge over the Mystic River, between the Assembly Square Orange Line station and the casino, which Encore operator Wynn Resorts is currently paying to design; improvements to existing bus service; and municipal policy changes to reduce parking requirements at new residential developments.

All the new development may also require more service on the Orange Line, even beyond the current plan to reduce wait times between trains from six minutes to 4.5 in the coming years. Dropping wait times to as low as 3 minutes during rush hour would likely require the agency to buy more new trains than the 152 cars that are expected to come online over the next few years, though Pollack said that would be a longer-term ambition.

The study did not identify a funding source, but officials said they will begin making these projects a priority and finding money for them in the coming years. They noted that private developers, Wynn Resorts, and the Massachusetts Gaming Commission may provide some of the resources.