I would support regenerative braking, but I do not think it is a massive contribution since braking happens year-round, but overheating is predominantly a summe

I would support regenerative braking, but I do not think it is a massive contribution since braking happens year-round, but overheating is predominantly a summer problem! Yes everything gets hot, including the clay, but the clay does not spontaneously heat up, the heat has to come from somewhere and what I am suggesting is that its being reradiated from trains which have been solar irradiated on the overground section, which is why the problem did not happen in the early days of the Tube when it was all underground, and does not happen on Glasgow’s, Warsaw’s or Prague’s networks which are solely/predominantly underground. The principle is that the solar barriers stop the heat entering the tunnel so there will be no need to carry heat out!