Maryland is officially recommending the state build two express lanes in each direction from the Potomac River and the American Legion Bridge all the way up to Gaithersburg on I-270. The state announced its preferred plan out of seven options on Wednesday.

The 12-mile stretch would allow vehicles with three or more people, including transit buses, to ride for free. Others could pay a variable toll to get out of congestion. The setup would be similar to Virginia’s Express Lanes. MDOT is seeking a private partner to finance and operate the lanes.

Here’s a map of where the proposed lanes would go.

Several environmental and other groups are pushing back on the road expansion, saying it’s too costly to parkland and streams nearby, and would contribute to car-centric sprawl and development. They’re arguing for expanded mass transit in the corridors.

Maryland’s latest proposal is part of a years-long attempt to reduce congestion on the Beltway and I-270. This is the first phase of what Maryland hopes will be a larger project of bringing toll lanes to much of the Beltway in the state.

The plan would add two “High Occupancy Toll” lanes in each direction on I-495. Then on I-270, one existing HOV lane (essentially a carpool lane that allows vehicles with two or more people) in each direction would be converted into a HOT lane, and another HOT lane would be added as well.

The proposal also adds bike and pedestrian connections across a revamped American Legion Bridge over the Potomac River. It also proposes transit improvements like an expanded bus capacity at the Shady Grove Metro stations and more park and ride facilities.

“In addition to delivering significant congestion relief in the existing free lanes, this… provides Marylanders with new travel options including free use of the new managed lanes for carpoolers and transit riders, new bike and pedestrian connections in the community and across the Potomac to the C&O Canal, and a consistent reliable transportation network for the entire National Capital Region from Maryland into Virginia,” MDOT Secretary Gregory Slater said in a statement. “Addressing the congestion bottleneck at the American Legion Bridge and identifying a strategy to replace this 60-year-old infrastructure element of the regional transportation network is critical to Maryland’s economic recovery and growth.”

MDOT says it won’t move ahead with other phases around the Beltway until more environmental reviews and public engagement are complete.

A Record of Decision, the final approval or disapproval from the federal government, is expected this fall, MDOT says.

A vote from the Maryland Board of Public Works would also be needed before the project gets the go-ahead.