Even as Maryland’s $5.6 billion public-private partnership for the Purple Line project is on the verge of collapsing mid-construction, the state is continuing to pursue a similar arrangement to add toll lanes to the Capital Beltway and Interstate 270.

State highway officials said they will work with companies earlier on the toll lane project to refine designs and cost estimates before any deal is signed. Hashing out such details via a “predevelopment agreement,” they said, would prevent the kind of unexpected costs that have left the Purple Line’s private concessionaire preparing to quit in mid-October.

In a briefing to the Prince George’s County Council last week, state highway officials also reiterated promises that the lanes will come at “no net cost” to the state. Council members asked how that squared with a state study released in July that found government subsidies of $482 million to $1 billion could be required, depending on how toll revenue stacks up against construction and financing costs.

Lisa Choplin, the toll lane project director, said the state will work with the concessionaire during the “predevelopment” phase to ensure that the firms’ financing package would require no state contributions. The private partners also will reimburse the state for what it is spending on the environmental study, state officials said.

Maryland Gov. Larry Hogan (R) has said companies will pay to widen the two highways and rebuild the existing lanes in exchange for keeping most of the toll revenue over 50 years. A state study found the two options that would provide the greatest traffic relief would cost $8.7 billion to $10 billion to build.

“It’s the governor’s commitment that this would have no net cost to the state,” Choplin told council members. “If it doesn’t pencil [out], then we have the ability to not go further.”

Added deputy project director Jeff Folden, “We are absolutely committed to working with the developer to ensure that when we get to financial close, it’s not going to cost the state taxpayer dollars. If we can’t reach that agreement, then we wouldn’t sign that deal.”

But the impending dissolution of the Purple Line’s 36-year public-private partnership hung heavily over discussions about the toll lane proposal. Maryland transit officials had told the council in a briefing a couple of hours earlier that the light-rail contractor had stopped construction and begun packing along 16 miles of building sites in preparation for leaving.

Under the Purple Line agreement signed in 2016, the private concessionaire, Purple Line Transit Partners, was to build the rail line, help finance its construction and then operate it for 30 years in exchange for annual payments from the state.

However, PLTP says the state owes it $800 million related to more than 2½ years of construction delays. The state is preparing to take over the project after PLTP’s expected departure next month, and both are suing each other over accusations of violating the project’s 876-page contract.

Council member Deni Taveras (D-District 2) sounded skeptical that a public-private partnership for the toll lanes project would go more smoothly.

“We currently have a bad taste in our mouth regarding the Purple Line and how it was structured and the damage that it has caused in some of our communities,” Taveras said.

Council member Dannielle M. Glaros (D-District 3) questioned how the state would prevent companies from cutting construction costs in ways that might harm communities. She said cost-saving changes proposed for the Purple Line would have left the Riverdale Park station atop a 26-foot-tall concrete wall through the area if the county hadn’t agreed to pay for a more airy bridge.

“I still don’t believe this won’t cost us money,” Glaros said of the toll lane plan. “I don’t think you’ll ever convince me of that.”

Choplin said the toll lane proposal and Purple Line are “different projects entirely.” On the toll lane project, she said, the state would reach a “predevelopment agreement” with the chosen companies. The state would then work with the companies, utilities, other state agencies and communities to refine construction cost estimates, reduce impacts and ensure the necessary right of way is included, she said.

“We are bringing on that potential developer earlier in the process,” Choplin said.

The Purple Line concessionaire has said major delays and cost overruns stemmed from CSX changing design requirements for a crash wall, the Maryland Department of the Environment changing storm water system rules, and disagreements over what right of way the state must provide.

“We’ll be eliminating risks so they don’t become issues,” Folden said. “All of the stakeholders’ needs are known, and we can move forward and have all that addressed . . . before we break ground.”

Prince George’s Council member Mel Franklin (D-At Large) questioned how state officials could guarantee no taxpayer money would be necessary when megaprojects often end up over budget.

“That risk is not something you can really dispense with completely,” Franklin said. “I’m sure the folks doing the Purple Line didn’t anticipate all that occurred.”

Under the state’s plan, teams of companies would add up to four toll lanes — two in each direction — to I-270 and the Maryland portion of the Beltway and build a new, wider American Legion Bridge. Toll rates would vary based on congestion to keep traffic moving at a minimum speed of 45 mph. The existing lanes would remain free.

State officials have said they plan to start with I-270 and the western part of the Beltway, between the Virginia side of the American Legion Bridge and the I-270 spur.

The state indefinitely postponed widening the top part of the Beltway after local officials objected following a state study showing that up to 34 homes could be destroyed. The rest of the Beltway through Prince George’s to Route 5 also has been delayed, with no time frame announced.

The public comment period on the project’s draft environmental study is scheduled to end Nov. 9, and state officials said they plan to announce a “preferred alternative” in the spring. Meanwhile, the state recently approved four teams of companies to submit proposals late this year. The state plans to select a winner in February and submit a contract to the state’s Board of Public Works for approval in March or April, Choplin said.

Hogan has said the state needs new ways to relieve some of the worst traffic congestion, which stifles job growth and harms residents’ quality of life. Opponents say widening the highways would cause too much environmental destruction, unfairly allow wealthier motorists to buy their way out of congestion and encourage auto-dependent sprawl development.