In fact, New York City has a history with articulated trains. In 1924, the Brooklyn-Manhattan Transit Corporation introduced plans for the “Triplex,” with a hinged, multisectioned body. It operated on the B, D, N, Q and R lines over a period of 40 years, representing “the height of transit modernity” at a moment when elevated lines often still featured wooden cars, according to the New York Transit Museum.

Today, many of the city’s subway cars are well past their prime, most strikingly those on the C line, known by their model number, R32, and for the tin-can siding that will continue rolling beneath Eighth Avenue for at least a few more years.

Though newer models now on the tracks are expected to last 30 to 40 more years, transit planners have urged the authority to consider articulated trains for any future fleet upgrades.

“We’re one of the largest systems in the world that doesn’t do it,” said Richard Barone, the director of transportation programs at the Regional Plan Association. “Our trains don’t function right now to allow people to circulate.”

Elsewhere, the trains have proved largely successful. Brad Ross, a spokesman for the Toronto Transit Commission, which began using an “open gangway” model two years ago, said capacity had increased by 8 percent to 10 percent.

In the model’s early months, Mr. Ross said, passengers would often let trains with traditional cars pass them by, preferring the features — or at least the novelty — of the new ones.