Maryland highway officials narrowed their options for expanding the Capital Beltway and Interstate 270 to one that would add four new high-occupancy toll lanes — two in each direction — to both highways. The state also committed to building sidewalks, bike paths and trail connections as part of the project, officials said Wednesday.

Four toll lanes, highway officials said, would provide the fastest and most reliable travel times. The state rejected six other options, including one that would have had reversible toll lanes on I-270.

Maryland Transportation Secretary Gregory I. Slater said the lanes would provide a “consistent, reliable transportation network,” starting with replacing the 60-year-old American Legion Bridge. Relieving that chronic traffic choke point, Slater said, “is critical to Maryland’s economic recovery and growth.”

As part of a federally required environmental analysis, Maryland officials selected the four-lane option as their “preferred alternative,” meaning it will be analyzed in more detail. The state’s Board of Public Works would have to approve any construction contract, which state highway officials say wouldn’t occur until late 2022, after the final environmental study is complete.

The Maryland State Highway Administration also is discussing with officials in Montgomery and Prince George’s counties ways to divert some of the toll revenue to local mass transit.

Provisions under discussion include expanding bus bays at the Shady Grove Metro station and the park-and-ride lot at the Westfield Montgomery Mall transit center. In Prince George’s, where any highway expansion would come later, state officials said high-frequency buses could use the Beltway HOT lanes between the Branch Avenue Metro station and the eastern terminus of the future light-rail Purple Line at the New Carrollton Metro station.

The state also reiterated a commitment to adding a pedestrian and cycling path to a new, wider American Legion Bridge, with connections to the trail along the C&O Canal.

The project’s draft environmental impact study released in July found that what’s known as “Alternative 9” would be “the most likely to be financially self-sufficient,” based on estimated construction costs and toll revenue. Maryland officials have said the lanes’ construction will come at “no net cost” to taxpayers because private companies will build the lanes and finance them in exchange for keeping most of the toll revenue via a 50-year public-private partnership.

The announcement of additional work to better serve pedestrians, cyclists and transit riders while also seeking to minimize harm to adjacent parkland appears aimed at appeasing the project’s critics. Those include lawmakers in both counties, local land-use planners, environmental groups and transit advocates who have said widening the highways would hurt the environment and give short shrift to mass transit.

Casey Anderson, chairman of the Montgomery Planning Board, said he was disappointed, but not surprised, that Maryland selected the four-lane option, even though it would damage public parkland bordering the Beltway.

“It seems like this is what they had in mind from the beginning,” Anderson said.

He said the state could have spared parkland and streams with a narrower highway footprint rather than boast of “environmental enhancement” projects it has planned. The stream restoration and water-quality improvement projects the state announced, Anderson said, are the kind of environmental mitigation it would be required to do under federal law.

“You’re supposed to look for ways to avoid impacts before you look for ways to mitigate the damage you’re going to do,” Anderson said.

He said he was disturbed by highway officials saying they had committed to “ongoing collaboration” with the Maryland-National Capital Park and Planning Commission, even though staffers there first learned of Wednesday’s preferred lanes configuration from a reporter.

“I thought we were supposed to be collaborating now,” Anderson said. “If this is their idea of collaboration, it’s not very promising.”

The selected alternative would add four lanes to the Beltway, between the Virginia side of the American Legion Bridge and west of Route 5. I-270 would get one new lane in each direction, in addition to the existing carpool lanes being converted into toll lanes.

Maryland officials have said they would begin with replacing the bridge. Construction would then proceed around the Beltway to the I-270 spur and up I-270. The part of I-270 between I-370 and Frederick is several years behind in the environmental review process. State officials postponed widening the Beltway east of the I-270 spur after a study found doing so would require destroying up to several dozen homes and harm more public parkland.

The toll lanes would be free to buses and vehicles with three or more passengers, which would match the HOT lanes on Virginia’s part of the Beltway. As in Virginia, toll prices would change with congestion to keep the toll lanes free-flowing. The regular lanes would remain free.

John Townsend, a spokesman for AAA Mid-Atlantic, said his organization pushed for the four toll lanes because they would provide the most traffic relief, including by moving vehicles out of the free lanes.

Expanding the American Legion Bridge, he said, is crucial to Maryland’s economic competitiveness with Northern Virginia, which already has more than 60 miles of HOT lanes.

“It will make Montgomery County viable again as a job creation center,” Townsend said.

The Maryland Department of Transportation has said it plans to announce in February a winner among three private teams seeking to build and finance the project.

Under the first “predevelopment” contract, the companies would work with local officials, property owners, residents and others for about a year to try to work through potential design problems before reaching a 50-year partnership with the state.

In Montgomery, the project would include replacing and widening the Bethesda Trolley Trail bridges over both highways and building a separated bikeway along northbound Rockville Pike over the Beltway, between Bethesda and Rockville.

A wider path along Seven Locks Road beneath the Beltway would connect Moses Morningstar Cemetery with Gibson Grove AME Church, officials said. The Beltway’s original construction in the early 1960s divided the historical African American community of Gibson Grove in the Cabin John area, leaving its cemetery on one side of the Beltway and its church on the other. Descendants have said they object to moving any graves to widen the Beltway.

In Prince George’s, Cherry Hill Road near Beltsville would get a shared-use path on two bridges over the Beltway to provide trail connections. New eight-foot sidewalks along Glenarden Parkway over the Beltway would link Glenarden neighborhoods, and the Henson Creek Trail would get a new connection near Temple Hills.

The state said also it would create a “strike team” of experts to find “innovative options” to reduce the impacts of a wider bridge on National Park Service land below. That includes Plummers Island, a 100-year-old sanctuary for Washington-area field biologists, who say a wider bridge would destroy a vital research site.