problems underground
How are the passengers maintained at normal atmospheric pressure and air flow, the slightest over or under pressure would destroy their lungs instantly. to have a self contained independent air supply would be heavy and bulky even for emergency use. Which brings to the point of breakdown 500 miles + from either end with no access points say within 100 miles how do you get them out as the tube would be blocked by their car( mechanical stuck fast) so air powered car of similar type would not work to get to it and even if you did get to it how do you get in and get passengers out. No insurance company would touch it without these answers so back to the drawing board as they say.
While I am here This may interest London underground users that travel to terminal 4 at London Heathrow airport (LHR). I was told by an electronic systems suppler at the time of building, that the surrey fire brigade( not London) rescue service did an exercise to get to people trapped in a train in the tunnel if the incident was half way along the firemen would not have enough air in their breathing apparatus to get to the train and BACK again. It would not be possible to carry extra cylinders due to weight of other equipment they would have to take with them and would not be able to give air to passengers. So smoke filled train no survivors. It was kept quite at the time but I wonder what the plan is now???.
