No, the Subway Doesn't Have to Be Insanely Hot and Gross

London cooled its tube subway system, at least some of the time. Why doesn't New York do the same thing?
September 6, 2018, 7:44pm

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Nothing captures the absurdity of summer life in America’s largest city like the descent into disgusting subway sweat. Even on a mild day, the platforms of New York City’s massive metro system run hot. It is the quintessential panorama of life here from roughly May to September: overcrowded platforms of people, each wiping away beads of grime and moisture as they wait anxiously for their salvation in the form of a (hopefully) air-conditioned train—assuming it’s not insanely delayed.

This is, of course, not a laughing matter: I know a handful of people personally who have fainted underground. On a particularly steamy day this August, officials from the Regional Plan Association (RPA), a tri-state transit policy group, brought thermometers down into some of the busiest hubs in the city. At 1 PM, a platform at 14th Street-Union Square—where seven MTA lines converge—reached 104 degrees. Another platform at the 59th Street-Columbus Circle stop clocked in at 101 degrees by 11 AM. Other major stations across Manhattan were shown to be in the 90s around the same time.

“If we don’t tackle the issue of heat in the subway, the public health impacts will continue to worsen as our planet and our city warms,” the organization argued in a press release.


But New York is not the only metropolis on the planet where the subway can resemble the seventh level of hell come August. The London Underground is a sprawling system that carries close to five million passengers a day, and, like New York, was built below ground over a century ago—which is to say it lacks modern-day ventilation. Depending on any given line’s age, some stations are more subterranean than others. And, sure, London’s average temperature during the summer months may be ten degrees cooler than that of New York, but that hasn’t stopped commuters from absolutely dreading that morning and evening descent.

The major difference here is that Transport for London (or TfL), the government body responsible for London’s public transit, decided to do something about it. About ten years ago, it started an initiative known as Cooling the Tube, which sought to introduce innovative engineering techniques into station design in order to alleviate at least some of the heat. And while the initiative is still very much a work in progress—like with any century-old system, overhauling it isn’t easy—it represents yet another lesson in mass transit an ostensibly modern city like New York would do well to borrow from its counterpart overseas.

"We completely understand that traveling can be uncomfortable during periods of hot weather and are investing millions of pounds to make the Tube and buses cooler for customers,” a spokesperson for TfL told VICE. “We are constantly working on new ways to keep the temperature down on the Tube and have doubled the number of fans on the network since 2012 as well as installing chiller units to pump in cold air. There are also 192 air conditioned trains serving 40 percent of the network.” (Still, the spokesperson advised, Underground customers should carry water wherever they go, and give their seat to someone who may appear faint.)


But before going into some of those techniques, it’s first worth understanding what makes a station so hot, and why they tend to stay that way.

Contrary to what you might think, it’s not the sheer volume of human bodies around you. Nor is it something we can chalk up to coming climate catastrophe, necessarily—rising surface-level temperatures do not substantially affect how hot stations get, either.

In a lecture last year, Sharon Duffy, then the head of station systems engineering at TfL, said that sweat-laden human bodies only contribute about 2 percent of the heat at Tube stations. The rest, she said, came from physics: 21 percent from the train’s actual movement; 15 percent from the train’s motor engine; 12 percent from the heat given off by the electrical and auxiliary systems installed to run said trains; and the majority—or over 50 percent—from the train hitting the brakes as it pulls into the station, an intense friction that gives off an exorbitant amount of warm air.

The problem, according to Duffy, is the mechanical ventilation that was built into certain stations—which New Yorkers would recognize as subway grates—only takes away about 10 percent of that heat. Many older, deeper stations on the Tube, she noted, weren’t even built with this ventilation, because at the time that they were constructed, they were freezing. This was a popular selling point at the time, she explained, but a reality that no longer rings true, since the clay above these stations has packed in a century worth of heat. Now it keeps heat in rather than out, turning that once-cool basement into a public sauna.


Meanwhile, the rush of sweet, sweet cool air an arriving train brings in only takes away 11 percent of the heat, according to her analysis. And setting up massive fans, which the Metropolitan Transit Authority (MTA) in New York is known to do, doesn’t get rid of any heat, she insisted, even if it does make you feel slightly better. That leaves behind about 80 percent of the original heat, which is what causes that pool of sweat to appear on your back in seconds time.

To find out more, a TfL spokesperson referred me to details on their website. One of the major experiments I came across was on the Victoria line, which carries about 200 million passengers each year. On that line, groundwater cooling, as it’s known, resembles an engineered A/C: at the Green Park station, five holes were dug into the ground to carry up water from an underground supply, or sump. That water is put through a water cooler—the opposite of a radiator—located above the platform, which, in turn, lets off chilled air to commuters below. The remaining water is then deposited back into a sewer.

But perhaps the most far-reaching innovation was the mid-tunnel ventilation system. Also installed on the Victoria line, this one is simple: in between stations, the hot air a train is giving off naturally rises through lift shafts, where above-ground ventilation systems await. Those systems then cool that warm air, and shoot it back down to commuters at the separate stations below. In total, 14 of the Victoria line shafts had been overhauled at the time of her speech, according to Duffy.


That’s not to say that the initiative doesn’t have its issues. London is like New York; finding space to do anything, let lone build ventilation shafts or water chillers above ground, isn’t always easy. And you need a lot of shafts to really make a difference at busier terminals. Then there’s the issue of cost-effectiveness: this level of engineering can be incredibly expensive, especially if work must be done to accommodate said construction. Both factors have stymied efforts to cool all stations citywide.

Going forward, TfL is looking at ways to utilize that heat to warm housing complexes, or generate electricity for the city at large, through a process called trigeneration. Newer stations like the Crossrail, slated to open next year, were set to have under-platform exhausts that target the heat’s biggest culprit: the brakes. Vents located underneath the platform filter that heat out through shafts, as the train is waiting at the platform.

That brings us back to New York. The latest stations added to the system—namely 34th Street-Hudson Yards, and the stops along the Second Avenue Subway—have what’s known as “air tempering,” where platforms are kept as much as ten degree coolers through air-conditioning, and pumps take air out to mechanical ventilation towers built near each station. But what about the other 470 or so subway stations that do not?

When I asked Shams Tarek, an MTA spokesperson, about what the system can do to beat the heat next summer, he said the agency’s strategy was solely to reduce the amount of the time you’re stuck standing on the platform. In other words, the less time you spend waiting for a train, the less time you spend being hot and miserable underground. (To date, there has been no serious talk of any London-scale engineering project on this side of the Atlantic.)


“Climate control didn’t exist when the subway system was built more than a century ago, and the air conditioning units on trains discharge a lot of heat into tunnels and stations,” he noted in an email. “We’re working hard to reduce delays so we can get our customers off the platforms and on their way in an air conditioned car.”

That’s what last year’s Subway Action Plan, and the currently unfunded Fast Forward plan, are for: to revive New York’s subway system from the “state of emergency” it has been festering in, and drag the city’s mass transit into the 21st century. The only problem is, the statistics haven’t gotten any better. And so, like coping with the delays, swimming through the sweat of New York’s subway stations is likely to remain a fact of summer life here for years to come.

Just make sure you bring water.

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