Traffic flows along interchanges that link I-495 and I-270 in Bethesda. (Katherine Frey/The Washington Post)

An ambitious plan to widen lanes on the Capital Beltway and Interstate 270 is entering a new phase with the release of a long list of possible construction alternatives this week.

Maryland transportation officials Tuesday unveiled 15 preliminary options that include the addition of congestion-priced toll lanes as well as dedicated bus lanes that would address traffic congestion on the two major highways. The alternatives provide the most detail of what the project might look like on I-270 and the Beltway.

Gov. Larry Hogan (R) in September proposed a $9 billion project to widen the highways to add managed toll lanes through a public-private partnership. The concept is now part of a complex federal review that explores a variety of possible improvements before settling on a preferred alternative.

The improvements under study include the addition of tolled and non-tolled lanes on both highways, bus lanes, spot improvements on the existing road to allow shoulder use and the conversion of existing HOV lanes to tolled lanes on I-270. Here’s the full list.

State officials say the goal is to find the best solution that not only provides some relief for commuters but also is financially viable.

“This is a massive undertaking,” Jeff Folden, a project deputy director with the Maryland State Highway Administration told a group of residents and officials at a meeting Tuesday night in Greenbelt.

“Current funding levels from the transportation trust fund could not accommodate this,” he said, noting that construction could take decades if they wait for public funding. “We are looking for something that can provide improvements in a self-sufficient manner. We are looking to see if any of these alternatives can be self-sufficient.”

Hogan’s proposal in September called for the construction of four toll lanes on each of the highways, potentially more than doubling the state’s existing toll network of 124 centerline miles.

Hogan is also proposing toll lanes for the Baltimore-Washington Parkway, which is owned by the National Park Service. That plan is contingent upon Maryland taking ownership of the 29-mile highway, and it would be run by the state’s transportation authority, not a public-private partnership.

The state and federal governments agreed to evaluate a state takeover, signaling a foreseeable transfer that would allow the state to pursue its plan to add four toll lanes to the roadway between Baltimore and Washington.

Hogan and his transportation team tout toll lanes as a way to ease traffic congestion and give Maryland commuters more choices. A public-private partnership would allow the state to make the improvements faster, and provide operations and maintenance more effectively without a big financial burden, Lisa Choplin, the P3 (public-private partnership) project director said.

As the area continues to grow, she said, the existing traffic conditions will only get worse if nothing is done. The project’s study area is home to some of the most unreliable freeway sections in Maryland, she said, where commuters experience speeds of less than 15 mph. The severe congestion lasts for seven hours each day on 1-270 and 10 hours on the Beltway, she said.

Tuesday’s meeting in Greenbelt was the first of four public forums where residents get a peek at the plan for the I-495 and I-270 Managed Lanes Study. The study covers the state’s portion of the Beltway between the American Legion and Woodrow Wilson bridges and I-270 between the Beltway and Gaithersburg.

Another study to tackle congestion on the entire length of I-270 will kick off next year, officials said.

The proposal for the Beltway and I-270 is part of the wider Traffic Relief Plan exploring solutions to address congested roads in the Washington and Baltimore areas. Choplin said the state has included over $7 billion worth of investment in transit through the Purple Line and the D.C. Metro.

“Now it’s time to address the highway improvements,” she said. “We are looking at system improvement and innovative solutions to address the congestion.”

Gina Davis, a Silver Spring resident whose home is two blocks from the Beltway, said she is concerned about the impact of a road widening on her property, the neighborhood schools and the YMCA.

“I am opposed to any widening of the Beltway,” Davis told a state highway official at Tuesday’s meeting. The official, who was fielding questions from residents in an open-house setting, said it’s still too early to say which, if any, homes would be taken.

Another resident said he was concerned that toll lanes in the Beltway and I-270 would generate tolls as high if not higher than those on Interstate 66 in Virginia, where motorists have paid nearly $50 to travel a 10-mile stretch. Others questioned whether the state’s goal is to move more cars or more people along the corridors.

The environmental-impact statement prepared by the Federal Highway Administration and Maryland Department of Transportation will include a review of existing and future traffic, roadway and environmental conditions. The list of alternatives is a starting point in a year-long process to identify the most feasible and effective alternatives for further study and then select a preferred option. The report will assess potential impacts.

The review is not expected to be completed until fall 2019 at the earliest.

More meetings are scheduled this and next week at 6:30 p.m. in the following locations:

Wednesday: Clarksburg High School, 22500 Wims Rd., Clarksburg

Tuesday, July 24: Central High School, 200 Cabin Branch Rd., Capitol Heights

Wednesday, July 25: Thomas W. Pyle Middle School, 6311 Wilson Lane, Bethesda