Traffic flows along interchanges that link I-495 and I-270 in Bethesda. Maryland is planing a multibillion project to rebuilt the Beltway and I-270 in what the state says will be the biggest such public-private partnership in the country. (Photo by Katherine Frey/The Washington Post)

Public comments submitted to Maryland transportation officials about a proposal to alleviate congestion on the Beltway and Interstate 270 raise concerns about widening the highways and the effect on private property. A top transportation official said Thursday the state intends to keep improvements within the existing right of way.

The project is part of Gov. Larry Hogan’s (R) $9 billion proposal to widen three of the state’s most congested highways — the Beltway, I-270 and the Baltimore-Washington Parkway — in what he said would include the biggest public-private partnership in the country.

The concept for the Beltway and I-270 is part of a federal review process that explores a range of improvements before settling on a preferred option. Last month, the Maryland State Highway Administration unveiled 15 possible construction options but left out details about their effects on residents.

“Everyone is concerned there are things we are not being told," said Lynn Marble, 72, a retired editor whose home is next to I-270. “They must have some idea of how that’s going to affect us."

Residents and elected officials have questioned why the state didn’t include the possible effects on private property as part of this first round of options. But state transportation officials say the exclusion of details isn’t unique to this project. They say the project is in its earliest stage of study and more details will come as the process moves forward and the public comment is received.

Detailed traffic, environmental and property studies will come later this year, said State Highway Administration spokeswoman Cathleen Gillen, as will drawings that show the potential effects on private property. Those will be presented to the public at workshops in the winter.

Maryland State Highway Administrator Greg Slater said the state plans to keep any changes within the existing right-of-way.

“There are many innovative solutions for transportation features in tight spaces around the world and we want to see them and others here in Maryland," he said.

State officials say the goal is to find the best solution that not only provides relief for commuters in some of the region’s most congested corridors, but also is financially viable. Commuters endure speeds below 15 mph during the most congested hours of the day along the two highways, state officials said. The severe congestion lasts for seven hours each day on 1-270 and 10 hours on the Beltway, according to state data.

“We are focused on doing this right, in a way that not only provides the greatest amount of congestion relief to Marylanders, but in a way that doesn’t disrupt their lives or communities,” Slater said.

For the past month, Marylanders have been able to review the 15 potential construction options. They include congestion-priced toll lanes, dedicated bus lanes, new non-tolled lanes and spot improvements on the existing road to allow shoulder use. They also include the conversion of existing HOV lanes to tolled lanes on I-270. Most options would require the widening of the roadways.

Critics said they doubt non-toll options are being seriously considered as the state pursues growth to its toll lane network. Hogan’s plan for I-270 and the Beltway calls for four toll lanes on each highway. The governor also envisions four 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, which would be run by the state’s transportation authority, rather than a public-private partnership.

The Maryland chapter of the Sierra Club called Hogan’s plan “misguided” and “deeply flawed." The addition of four toll lanes to the Beltway and I-270 would result in “even more traffic, demolishing our homes, and destroying our environment,” the group said.

Citizens Against Beltway Expansion, a group of residents and civic associations, has distributed fliers, set up meetings and organized on social media against the proposal. The city of Rockville, members of the Montgomery County Planning Board and some neighborhood civic associations say they oppose any project that would widen the footprint of the highways and affect private and public property.

“We urge (the Maryland Department of Transportation) to pursue mass transit, which is the only viable solution to lasting traffic congestion,” Rockville Mayor Bridget Donnell Newton said in a letter to the state last spring.

At a July meeting of the Montgomery County Planning Board, commissioners pressed State Highway Administration officials to release details of any potential width changes to the highways. They said residents can’t understand the project without knowing how much wider the state wants to make the highways or how high tolls would be to make the project financially viable.

Commissioner Natali Fani-Gonzalez scorned project leaders for presenting options about transit and non-toll improvements that she said aren’t likely to make the shortlist.

“Your whole proposal is not really about congestion," she said. “It is really about making money."

Nearly 600 people attended four public forums on the project last month. Residents have until Aug. 27 to comment on the first round of options. The state will then start the process of bringing down 15 options to about five or six by the end of the year. Officials hope to settle on a preferred construction option for each highway in fall 2019.