Many of Connecticut’s shoreline commuters would love a faster trip to New York City, but aging railroad bridges and a backlog of transportation projects pose a pricey stumbling block of at least $3 billion.

Both politicians and a Fairfield County business group argue that such an investment is worthwhile because faster trains between the two states would improve the region’s traffic flow and Connecticut’s economy. A recent 12-day disruption along Metro-North Railroad’s New Haven Line caused a $62 million drop in the gross state product, a measurement of economic output.

“This is the life blood of the economy here,” said Joseph McGee, vice president of public policy for the Business Council of Fairfield County.

McGee has advocated the “30-30-30” plan, which calls for 30-minute rail trips between Hartford and New Haven, New Haven and Stamford, and Stamford to Grand Central Terminal in New York. He contends faster speeds on the New Jersey Transit commuter rail line gave an economic boost to northern New Jersey. Connecticut legislators included $200,000 in the state budget to study the plan.

Democratic state Sen. Toni Harp recently proposed an hourlong ride from New Haven to New York as part of her economic development plan in a bid for mayor of New Haven. The trip currently takes about two hours.

Metro-North Railroad, which operates the commuter rail line, has been cool to the concept. And in an interview with The Associated Press, Connecticut Department of Transportation Commissioner James Redeker said that while he understands the desire to “bring Connecticut faster, closer to Manhattan,” the solution is more expensive and complicated than “30-30-30.”

“I see the 30-30-30 as a representation of what the business community would like to see for the New Haven Line,” he said, adding that limited resources must also be spent on improving highways, expanding access to public transportation and improving airports and ports.

“I need a strategy for the whole DOT,” he said. “I’m responsible for something bigger than the railroad.”

DOT recently unveiled an 18-to-20-month-long initiative called Transform CT to gauge the public’s desire for transportation improvements and then build a plan based on what the stakeholders want.

If people want rail upgrades, they should be prepared for a hefty price tag.

Despite the state having spent more than $3.2 billion on the New Haven Line over the past decade, with two-thirds from state bonds and the rest from federal funding, Redeker said at least $3 billion more of “state of good repair” needs are pending.

The backlog includes replacing and upgrading the overhead catenary lines, upgrading the antiquated mechanical signal system and addressing the aging railroad bridges, some of which are more than 100 years old.

Once such improvements are made, Redeker said, commuter train trips should speed up and any routine repairs and maintenance become less disruptive of service.

“If you could expedite the investment in that repair process, that upgrade process, the need to slow trains down during repair efforts or to bypass because of a wire system or a signal system disappear, and you can maximize speed at that point and frequency for that matter,” he said.

The DOT is already in the process of upgrading the catenary lines. The agency also is designing a new signal system and plans to address the immovable bridges. Redeker brought in outside experts to come up with a plan to build a replacement train bridge alongside the aging Atlantic Street Bridge in Stamford. Once complete, it can be popped into place over two weekends in 2016. Building it in place would take until 2024.

Redeker said movable bridges remain a big challenge to increasing speed. The New Haven Line has five, including the steel truss bridge over the Mianus River in Greenwich. Constructed in 1904, the bridge is operated by crews who make sure it closes perfectly after opening for marine traffic.

“People literally have to realign this structure with mechanical equipment, by hand,” he said.

Connecticut may benefit financially from its decision in the 1970s to retain ownership of the New Haven Line. A new federal rule could require Amtrak, which pays the state an access fee to use the line, to pay a share of the line’s infrastructure costs.

“When all is said and done, based on their proportionate share of traffic, it’s my belief that we’ll see some resources come into the system, which would be good,” Redeker said.

But he stresses that whatever extra money Amtrak provides, Connecticut won’t come close to the figure needed to cover the upgrades.

And the New Haven Line is not the only stretch that requires improvements. Altogether, the backlog of work along the Northeast Corridor represents a cost of about $52 billion.

A federal advisory commission, which Redeker oversees, is examining the financial responsibility of state and federal governments, as well as freight operators and other groups.