Windham — A Central New England freight train rolled slowly forward on a track behind Main Street on Tuesday morning until it crashed through a banner stretched across the tracks that read “Bringing Modern Freight Rail Service to Connecticut.”

A crowd of more than 60 people cheered and waved to the conductor as he motored past the white VIP tent at the rear of the Windham Chamber of Commerce office.

What was called the “most unique” and the “awesomest” ribbon-cutting ceremony in the region marked the start of construction for a much-touted $12.8 million freight rail upgrade project for the Central New England line that runs from New London through Montville, Norwich, Franklin, Willimantic and on to the Massachusetts border. There, the line ties into other Central New England tracks that run north into Canada.

The upgrades, with construction expected to start in spring, will allow the tracks to carry 286,000 pounds of freight, up from the current limit of 263,000 pounds. The improvement is expected to invigorate freight traffic on the tracks, allowing numerous manufacturing plants along its rails — including some of Norwich's biggest taxpayers — to expand operations and bring more traffic to the Port of New London.

The tracks end, or begin, at State Pier, now part of the Port of New London.

“This corridor is eastern Connecticut's opening to the world,” said Scott Bates, chairman of the Connecticut Port Authority, which runs the New London port.

New London Mayor Michael Passero said the rail upgrade project could be the most significant economic development advancement for New London “in decades.”

With much lobbying from local, state and federal lawmakers, the region was successful in 2014 in its third attempt to obtain highly competitive federal Transportation Investment Generating Economic Recovery — TIGER — for the project. The $8 million grant will be added to the $4.8 million contributed by Genessee & Wyoming Inc., owner of the Central New England line.

Dave Brown, CEO of Genessee & Wyoming, said company officials realized immediately upon purchasing the historical line that it needed a major upgrade. Bolted rails will be replaced with welded lines. New ties will be installed, bridges upgraded and street crossings improved, officials said Tuesday.

Brown cautioned municipal leaders that they might receive some complaints about noise along the way, and apologized in advance for any disruptions to local residents and businesses.

Brown said the exact time schedule and location for construction are not yet set for the project. All work will be done within the existing railroad right of way, with no property acquisition needed. While the new lines will be able to bear heavier trains, he said, the size of the train cars would remain the same for now.

Similar upgrades have been done to the Central New England lines in Vermont and New Hampshire, Brown said, and are underway in Massachusetts.

Amit Bose, a representative of the Federal Railroad Administration, said Connecticut spoke with a loud, unified voice in favor of the TIGER grant for the Central New England line. The application was among nearly 800 applications for the TIGER funds and one of the 72 that were approved.

Speakers Tuesday included U.S. Rep. Joe Courtney, D-2nd District, and U.S. Sens. Richard Blumenthal and Chris Murphy, both D-Conn. The congressional delegation has held meetings with local and state officials to support the TIGER grant application and rode a charter train car from New London to Massachusetts in 2012 to demonstrate the importance of the route.

Along the way, the train passed by rail-dependent industries in Montville, Norwich and Franklin. Participants then and again on Tuesday touted the future potential of adding passenger trains to the line, connecting riders to universities and tourist attractions, including fall foliage views in the rural northeast corner.

“People understood the value,” Courtney said. “The tracks go right to the Port of New London. It was a case where we felt the full effort was well worth it.”

c.bessette@theday.com