Map shows the route of a proposed Purple Line light-rail line. (Gene Thorp/The Washington Post)

A proposed light-rail Purple Line through Montgomery and Prince George’s counties is a “good candidate” for being built via a public-private partnership, a top Maryland transit official wrote recently to state and local elected leaders.

The proposed 16-mile rail  link between Bethesda and New Carrollton is suitable for private investment due to the project’s size and complexity and because it could be built and operated independently of the Washington region’s other rail systems, according to the letter e-mailed Monday by James L. Knighton, director of the Maryland Transit Administration’s governmental affairs office. The Washington area also is familiar with other transportation projects built via public-private partnerships, the letter said.

Such partnerships are easier to do in Maryland now because of new legislation that streamlined and clarified the process, state officials have said.

The state transit agency recently sought ideas from private companies for ways they could help build and pay for a Purple Line’s construction.

State officials have said having a consortium of companies help design and build the line, while also being responsible for operating and maintaining it, would help guarantee a high-quality project that would run well and would last.

A Purple Line, which would have 21 stations and two-car trains running mostly along streets, is estimated to cost $2.2 billion to build. The line would be designed to connect Maryland’s ends of the Metrorail system with Amtrak and commuter rail stations, and to spur redevelopment around stations in older, inner suburbs.

State transit officials are still analyzing the potential for private investment for a 14-mile light-rail Red Line in Baltimore, Knighton’s letter said. That project is estimated to cost $2.6 billion to build.

Maryland’s new transportation secretary, James T. Smith Jr., was quoted in recent media reports saying that he’s confident that the state can build both rail projects. Smith reportedly cited the potential for private investment, as well as additional public revenues anticipated from a new sales tax on gasoline that began to kick in Monday.

However, Smith also was quoted as saying the Red Line still had some local opposition to overcome. A Purple Line also has faced opposition from the Town of Chevy Chase and Columbia Country Club, which abut a wooded biking and running trail that critics say a Purple Line would destroy.

Both transit proposals also would have to win highly competitive federal transit aid to cover half of their construction costs, state officials have said.