Dozens of aluminum-coated train cars sit disconnected outside a warehouse at New Haven’s Union Station, waiting in line to be repaired. While running, their exterior paint is chipped, their navy and red plastic seats are torn, and their air conditioning struggles to cool down the standing-room-only crowd — if it is functioning.

Carrying 110,000 passengers to and from their jobs in New York and Connecticut every day, the New Haven line of Metro-North Railroad is the one the nation’s busiest. The 350-car New Haven-based fleet includes 241 cars that were purchased 30 years ago. State officials embarked earlier this year on a $149 million, six-year plan to refurbish the aging trains by replacing their critical parts.

The trains have 30-year-old technology, said Harry Harris, chief of public transportation for the state Department of Transportation. He said the basic frame of the equipment is structurally sound, but the technological equipment is a problem.

As long as Connecticut remains strapped for cash, funding for new cars will be put on the back burner, Harris said. Such an endeavor would likely cost over $1 billion — even though new cars cost $5 million, an average car can be refurbished for $800,000.

“Eventually we will have to replace the fleet,” Harris said. “We are taking a real hard look as for which direction we should take for the next generation.”

Metro-North spokesman Dan Brucker said the New Haven line fleet is the company’s oldest and busiest. With more commuters riding trains to avoid traffic, he said the fleet will need to expand soon to 400 trains to meet demand.

“On the New Haven line we are looking at our aging fleet needing major overhauls and rebuilding to serve an ever-growing ridership,” Brucker said. “More and more people are traveling further distances on ever-older equipment.”

The logical choice for the state to make, Brucker said, is to replace the aging trains. But the state’s attention has focused recently on other transportation projects, including a $300 million effort to replace overhead wires above the tracks on the New Haven line, which date back to 1913, he said.

“This fleet is reaching the end of its economic life, meaning they will have expensive repairs and will make their usage simply not the most logical approach,” Brucker said.

The New Haven line trains, two-thirds of which were purchased between 1972 and 1975, were intended to last 25 years and the state is trying to breathe a few more years of life into them, said Jim Cameron, spokesman for the Connecticut Metro-North Rail Commuter Council, a commuter advocacy group.

While state officials denied that safety was an issue with the old cars, Cameron said there have been four train fires in the last year-and-a-half. He said it was fortunate that those fires occurred aboveground and nobody was injured, but he expressed concern that a tunnel fire could happen.

“Given the way Hartford tends to work where it takes a crisis to force change, I am fearful that it will take a crisis on a train, a fire with some injuries, before Hartford says maybe we ought to find the money to order these new cars,” Cameron said.

Harris said the aging cars only pose reliability concerns, not safety ones. Walter Spear, 52, who commutes via Metro-North to New York from New Haven, said he has rarely felt unsafe on board.

“Once in a blue moon you’ll be in a car when the car will be shaking and rolling,” Spear said. “They’re not the most comfortable in the world. I’ve traveled on Amtrak and Eurostar and there’s no comparison. But they’re better than the subways of New York.”