Subsurface trainsIn 2010, new S-stock trains were delivered to replace the A, C and D stock trains on the subsurface Lines (Metropolitan, Circle, Hammersmith & City, and District). These have standard air-conditioning, as the subsurface tunnels are large enough to displace the exhausted hot air.
Well, according to Engineering & Technology, one major reason is there has to be somewhere to vent the hot air pushed out of the carriages by the air conditioning systems, otherwise it would just heat them even more. Building new ventilation shafts for the deep Tube lines would just be an incredibly expensive task.
In July and August, the average tube temperature can be over 29°C. Note: The Deep Level lines are Bakerloo, Central, Jubilee, Northern, Piccadilly, Victoria, and Waterloo and City. Sub-surface lines are the Circle, Hammersmith & City, District and Metropolitan lines.
In most New York City subway cars, the air-conditioning works. But if you find yourself in a hot car, the journey can be excruciating. Just ask the riders of Car 1859. Sign up for Your Places: Extreme Weather.
Instead, air is passively released through ceiling grates and circulated when trains blast through the tunnels. (It's impossible to provide air conditioning in stations, because the system wasn't built with space for the machinery, and there are too many openings to the street.)
Wear light clothing. Even if you think you might need to wear a jacket, when you are on the hot Tube, it's likely you'll want to take it off immediately. Heavy, dark, thick clothing will make you more likely to sweat, and hold on to the sweat your body does produce – keeping you hot and clammy for longer.
High temperatures can impact Amtrak operations as the extreme heat can cause rail, bridge and catenary wires to expand. As a safety measure, Amtrak imposes heat restrictions, which require locomotive engineers to operate trains at lower speeds than under normal operating conditions.
The Channel Tunnel (French: Tunnel sous la Manche), also known as the Chunnel, is a 50.46-kilometre (31.35 mi) underwater railway tunnel that connects Folkestone (Kent, England) with Coquelles (Pas-de-Calais, France) beneath the English Channel at the Strait of Dover.
THE world's deepest metro system is the Pyongyang Metro in North Korea which is 110 meters deep. The tunnel was built as part of an underground military facility. THE world's deepest metro, underground station is the Arsenalna Station on the Kiev Metro in Ukraine, at 107 meters deep.
Decades of accumulated heat from train brakes; which get hot from friction and heat up the air. With limited ventilation, there's no real way for the hot air to escape quickly. That's the case in London and I can imagine it is very much in the same in New York.