Commuters are travelling in temperatures on the London Underground that would be illegal to transport livestock in, according to new reports.
As Britain basks in balmy temperatures to rival the Mediterranean, life on London's packed Tube lines and buses is less than comfortable.
According to the Evening Standard, temperatures on the Central Line on Wednesday reached a brow-mopping 34.8C and air humidity hit 45 per cent.
Bus passengers were also feeling the heat, with some services hitting 35.5C on the top deck, more than 5C hotter than the maximum of 30C allowed to transport cattle.
Speaking to the paper, Transport for London (TfL), pledged to make more improvements.
It said that by 2016 it will have tripled the number of air conditioned Tube trains to cover 40 per cent of the network services.
According to the Metro, David Waboso CBE, capital programmes director at London Underground, admitted there is still much to do.
He said: "We are investing millions to keep temperatures cool for passengers. New air conditioned trains are now operating on the Metropolitan, Circle, Hammersmith & City and are currently being rolled out on the Wimbledon to Edgware Road branch of the District line.
"By 2016, an air conditioned service of 191 trains will be in operation covering 40 per cent of the Tube network.
"But we know there is still much to do and cooling the other deeper lines of the Tube remains a considerable engineering challenge."
Passengers on the route 10 bus from Oxford Circus to Hammersmith on Wednesday experienced 35.5C on the top deck bemoaned the fact there were no windows open.
Speaking to the Evening Standard, Ella Goodman, 31, a PA from Wallington, said: "Just a crack of a window would make so much difference, but this is the first time I've noticed that on these new buses they haven't actually got any windows.
"The air con doesn't really seem to work. It's very uncomfortable, makes you feel you don't want to be on it and it makes you really lethargic.
"It just seems like they should have windows."
And, according to the Independent, a host of commuters have been venting their heat frustrations on social media.
One user Robyn Mellor tweeted: "London Underground u suck when it's hot and need to get better Ventilation! Can't wait for the day that I don't have to travel on there!"
Another, Callum Ross, wrote: "Descending into the London Underground is like descending into hell. Except hell isn't quite as hot and hell's people are more pleasant."
Have you been suffering in unbearably hot conditions on London's transport networks? Leave your comments below.
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