NEW YORK » It was called the "First All-American Tush Tally," an informal test to measure the behinds of two dozen New Yorkers to see if they could fit into the prescribed space in new subway cars made by Kawasaki.

The seats were about 17 inches wide; the rears ranged between 13 and 23 inches wide. The organizer of the tush tally was Carol Greitzer, then on the City Council. The year was 1984.

The problem of American waists that are too big for seats meant to accommodate them is certainly not new. Today, everything from love seats to toilet seats can be built bigger to accommodate wider profiles, and the seats offered on public transportation are no different.

Each time an agency decides to purchase new trains or buses, it must consider whether to make its seats wider, knowing that a decision to do so could come at the expense of passenger capacity.

New Jersey Transit has a five-year plan to add 100 double-decker train cars that have seats 2.2 inches wider than the 17.55-inch seats found in its single-deck trains; the seating configuration has been changed to two seats on either side of the aisle, rather than three on one side and two on the other.

Amtrak intends to introduce "designs that will be able to accommodate the larger-sized passengers" on 25 new dining cars starting next year, said a spokesman, Cliff Cole.

But while transit agencies consider the needs of heavier passengers, they do not always yield to them.

Over the past half-century, the width of New York City subway seats has not changed much, said Marcia Ely, assistant director of the New York Transit Museum. If anything, the seats have occasionally gotten smaller — and immediately encountered resistance.

The subway cars made by Kawasaki, the R-62 model, are still around on the No. 3 line. The bucket seats are still too narrow, Greitzer noted.

"It’s particularly annoying now when they’re wearing winter clothing," she said. "People are much bigger and heavier than they used to be."

The airline industry has also spent years trying to balance passengers’ desire for bigger, more comfortable seating with the bottom-line-driven inclination to squeeze as many seats as possible onto an aircraft.

"It is becoming much more of an issue for transportation, trains, buses," said Katharine Hunter-Zaworski, director of the National Center for Accessible Transportation at Oregon State University. "You can only make the trains so wide."

The Port Authority Trans-Hudson (PATH), which generally caters to riders with shorter commutes than those who use the commuter railroads, decided not to change the seat width when it finished replacing its fleet of 340 rail cars last year.

The Metro-North and Long Island railroads are expected to request bids for a new fleet of M-9 train cars next month. In their preliminary proposal, the railroads have asked for double seats that can handle a 400-pound load, but they did not change their seat width.

Cesar Vergara, an industrial designer who worked with Metro-North on its M-8 cars and whose plans will remain the same for the new bid, said the 58-inch-wide three-seaters have middle seats designed to look larger.

"The seats were sewn so that the center part looks a little wider and more appealing," Vergara said.

Heavier passengers are also a problem for national agencies creating crash-test standards for trains and buses. While it does not deal directly with width, the Federal Transit Administration has proposed to raise the standard for bus testing to 175 pounds and 1.75 square feet per passenger, from 150 pounds and 1.5 square feet. A committee for American Society of Mechanical Engineers is evaluating its crash-worthiness standard and plans to adopt a new one by April.

"It’s clear that the U.S. population is getting heavier," said Martin Schroeder, chief engineer for the American Public Transport Association and the committee’s chairman. "We are trying to get our hands on that and figure out what is the best average weight to use."

Seat width is just one of many things that transit agencies have to factor in when they are purchasing new train cars.

When PATH officials were working on buying their new 340 cars, said Ron Marsico, a spokesman for the Port Authority of New York and New Jersey, they had to consider adding more lumbar support in seats and room for broad-shouldered passengers. The officials also had to grapple with changes unrelated to customer comfort, like removing seats to make room for updated automatic train control equipment and complying with disabilities requirements.

New Jersey Transit decided to make wider seats a priority after hearing from riders, a spokesman, John D’Urso, said. The agency took the request to the manufacturer Bombardier, which had its seat maker, Kustom Seating, build the seats. Bill Luebke, manager of engineering for Kustom Seating, of Bellwood, Ill., said the company designed the seats to be comfortable for riders ranging from a woman in the 5th percentile to a man in the 95th percentile.

Sandra Lee, 39, a slender commuter on New Jersey Transit and PATH, said that the seats on PATH trains were too narrow and that she preferred the seats on New Jersey Transit’s newer double-decker cars because she found them more comfortable, if not wider.

"I happen to be hippy," Lee said. "So I take up the width of it."