Maryland transit officials have touted construction of a light-rail Purple Line as a way to shape communities in Montgomery and Prince George’s counties for decades to come — and that’s exactly what makes some residents nervous.

After the Maryland Transit Administration put the $2.37 billion project out to bid last week , residents along the 16-mile alignment scoured the 2,200 pages of bid documents for assurances that the winner would have to pay close attention to the Purple Line’s impacts on their neighborhoods.

It’s almost unheard of for citizens to get involved in the details of a highly technical government contract. However, some residents say they are concerned about the private sector’s unusually extensive role in the project via a 35-year public-private partnership that would cover all aspects, from designing and building the line to operating and maintaining it.

INTERACTIVE GRAPHIC: Mapping the proposed Purple Line

In communities such as North Chevy Chase, Bethesda, Silver Spring, Long Branch and Langley Park, even Purple Line supporters say bidders should have to meet more specific and stringent requirements to reduce train noise and vibrations, replace torn-out trees, make the trains’ electrical substations less intrusive, and help small businesses weather years of construction.

“In our past experience, the local communities get left out,” said Zorayda Moreira-Smith, of Casa de Maryland, a group that assists low-income immigrants in the Langley Park area. The group supports a Purple Line.

“We want these issues to be a priority,” Moreira-Smith said, “not an afterthought.”

The Purple Line would be Maryland’s first public-private partnership on a major transportation project and would rely on the private sector more extensively than almost any other U.S. transit project because the contractor also would help finance construction.

The MTA released a “request for proposals” Tuesday, formally beginning the bid process. Proposals from four previously selected teams of private companies are due Jan. 9, and state officials say they will select a preferred bid in spring 2015. If the project secures federal aid, state officials have said construction could begin in 2015 with the line opening in 2020.

What makes many community groups nervous is that unlike with a traditional transit contract, the project is going out to bid with only about 30 percent of it already designed by the Maryland Transit Administration. As long as bidders meet certain requirements, such as federal noise limits or the Americans With Disabilities Act, many of the details of what the line would look and sound like will be left to a private sector motivated by profit.

In the Silver Spring community of Lyttonsville, residents wanted the state to require that bids include an elevator to help people with disabilities reach the Purple Line station, rather than a 200-foot ramp that state plans showed. An elevator would be more expensive, but residents say a ramp would be too long for people with canes or walkers. Without the state requiring an elevator, they say, bidders will stick with the cheaper ramp option to remain competitive.

The Hamlet Place townhouse community in Chevy Chase is worried about privacy. The four-foot sound walls that the bid solicitation requires as a minimum height would allow train passengers to see into their living room and bedroom windows, said Guy Scango, chairman of the community’s Purple Line committee.

“The [bidders] are going to try to save money,” Scango said. “Unless something in the [bid specifications] tells them to do something, they have no contractual responsibility to do it.”

A Purple Line between Bethesda and New Carrollton would have 21 stations. Trains would run mostly along local streets to connect Metrorail lines with Amtrak and MARC commuter rail stations. Supporters say it would provide faster and more reliable east-west transit than buses and revitalize older suburbs, particularly in Prince George’s County.

Henry Kay, the MTA’s head of new transit project development, said the sensitivity of the procurement process prohibited him from discussing many details of the bid solicitation. However, he pointed to requirements that contractors abide by both federal and industry standards for noise and vibrations, both during construction and the trains’ operations.

He said the contractor also would have to abide by the federally approved “record of decision,” which spells out the state’s legally binding commitments to reduce impacts on the environment and neighborhoods. How the contractor meets those commitments, however, will be left to the bid proposals.

“We’re telling them [bidders] what we need to achieve and then leaving up to them how to achieve it,” Kay said.

He said the state could withhold payments to the contractor, both during construction and the line’s operations, if any of the standards, such as noise limits, aren’t met.

Communities’ desire for some kind of legal assurances — and complaints that state transit officials have too often dismissed their concerns — have fallen on sympathetic ears. Montgomery County Executive Isiah Leggett (D) recently formed a Purple Line Implementation Advisory Group to allow residents to meet twice a month with county and state officials.

“These are not minor concerns,” said Leggett, a Purple Line supporter. The train noise and vibrations “will affect many people for a lifetime. If we need more time to get it right or need to pay a little more to address it, I think we need to do it earlier [in the contracting process] than later.”

State officials said they have held nearly 2,000 public meetings and outreach events over the past two years and have made design changes in response to community concerns. Those included better shielding a Purple Line train maintenance facility from homes in Lyttonsville.

Kay said the winning contractor will have to meet with community groups, too.

“We at MTA will be there to bring the community and the contractor together to talk about design details,” Kay said.

Most of the community outcry has been in Montgomery, where much of the line would run through neighborhoods and adjacent to homes that now back up to the wooded Georgetown Branch trail.

In Prince George’s, trains would run more in the middle of busy roads, much of it in heavily commercial areas.

Prince George’s officials say they hear more from residents who want better transit and the economic development a Purple Line is expected to bring than from those worried about neighborhood impacts.

“When I talk to people about the Purple Line, they just want it built quicker,” said Prince George’s County Council member Eric Olson (D-College Park), whose district includes much of the route.

David S. Iannucci, a senior economic development adviser to Prince George’s County Executive Rushern L. Baker III (D), called the Purple Line a “critical breakthrough for Prince George’s County,” something county officials hope will spur economic development and grow the county’s tax base.

Iannucci said the only community concerns he’s heard have come from small-business owners worried about customers reaching them during a rail line’s construction and from people concerned about rents remaining affordable amid new development.

He said the county plans to create “some kind of formalized process” to hear community concerns.

“We want to make sure that communities embrace the Purple Line not just because it’s good for transportation and good for Prince George’s’ overall economy,” Iannucci said, “but also good for specific communities.”