Thousands of London commuters endured temperatures of nearly 100F after their packed Tube trains became stranded for more than an hour yesterday.
Thirty people had to be treated for heat exhaustion once they were freed from four Victoria Line trains and 17 others needed hospital treatment.
Their ordeal came on one of the hottest days of the year and increased the pressure on London Underground to introduce air-conditioning systems. It also came on a day when LU launched an initiative designed to placate passengers, by offering free bottles of mineral water at two stations.
Problems began when a train leaving Highbury and Islington station in north London stopped when a safety system was set off just before 9.30am. A passenger is believed to have triggered a device on the outside of the train to open doors.
While that fault was investigated three other trains stacked up in the tunnel approaching the station. Passengers were led off the original train, whose last carriage was still on the platform, and the one behind it was brought forward to allow people off.
Both those trains developed faults, though, and could not move. Eventually passengers from the remaining two trains walked through the carriages and on to the platform, after some of them had been trapped for an hour and a half. Witnesses told of passengers having asthma and panic attacks, with some collapsing.
Ralph Hodgson, a college lecturer, said: "The heat became quite unbelievable. People started to collapse on the floor. Some people... became extremely disturbed, standing or sitting there crying."
Sara Wallis, a 22-year-old student, said: "There were kids crying, there were elderly people needing to sit down... at least half a dozen people were rushed through suffering from heat exhaustion."
As passengers emerged at the surface there were chaotic scenes in the station. Hundreds of people waited for water provided by paramedics. London Ambulance service sent 15 vehicles to the station.
London Underground said it was investigating the cause of the original breakdown with British Transport Police and "passenger misuse" of a safety device was a possibility.
Tube trains have air conditioning only on the new Jubilee Line extension. It is unlikely to be introduced elsewhere because of the cost and engineering work involved.
The free water offer at Oxford Circus and Piccadilly Circus stations was greeted with derision yesterday. Andrew Bosi, chairman of Capital Transport Campaign, said: "Will passengers even have enough elbow room to open their bottle?"Reuse content