NEW YORK (PIX11) — If New York City ran more trains or reduced the cold air inside subway cars, it could ease the suffering on sweltering platforms, experts said.

One of the biggest culprits for the hot and steamy platforms is the air conditioning units that cool the cars give off a lot of heat, according to Rachel Weinberger, the Peter W. Herman Chair of Transportation for the Regional Plan Association.

“The only thing that AC does is move hot air to places where the air is otherwise cooler — and because it is done by using a motor to move pressurized gas through a system, it adds heat in the process,” Weinberger said in a statement to PIX11.

“It’s like standing behind a fridge,” said Danny Pearlstein, Policy and Communications Director for Riders Alliance.

The subway system transfers air via a push-pull system. As trains enter a station, the existing air is pushed out of the ventilator grates at street level, according to an MTA source. When the trains leave, the air is pulled in from the outside via the grates.

The platforms one floor below street level tend to be the hottest, and those several flights below the street are a bit more bearable for riders, Pearlstein said. The above-ground platforms provide some shade from the sun but are otherwise no different than standing outside.

“If they ran more trains, there would be less people on the platforms, and the wait times would be less,” Pearlstein said.

The Nos. 4, 5, and 6 platforms at Grand Central Station are the only ones that have air conditioning because they are powered by Grand Central’s cooling system, and it’s too expensive to install in the rest of the subway lines.

Some of the hottest stations tend to correlate with the busiest ones, including Penn Station, Union Square, and Columbus Circle, according to a report from the RPA.

“Some of the waits can be punishing,” Pearlstein said. “It can be dangerous.”

A few years ago, the RPA recommended a few changes that could ease the heat in the city’s transit system, including reducing the amount of air conditioning in the cars to control the heat on the platforms. The agency also suggested the city open up the stations for more light and air and build more energy-efficient subway lines.

However, experts conceded that such projects, and even more subway service, are unlikely due to funding.

PIX11’s Greg Mocker contributed to this report.