[onetimeuse92304]

Oh, so this is exactly like budgeting. It does not matter a lot how much something costs, what matters is where the money came from.

Here we improve the trains to emit less heat and immediately spend it on air conditioning.

In the meantime the debt (tunnel excess heat) continues to rise and somebody else in the future will have to pay for it.

[NamTaf]

It's more like budgeting at a home level, in that you have a set limit of heat that you can spend, and choosing to spend it less on equipment like brakes, traction motors, etc. and more on air conditioning means still remaining in budget.

Their overall limit of heat output by the trains remains the same. The tunnels won't be any hotter than they are now, thanks to savings found in other systems.

[onetimeuse92304]

No, it is more like government spending. It is like saying, "we need to be fiscally responsible and that means only spending no more than 160% of what we are earning".

The tunnels are getting hotter and hotter. Saying "the tunnels won't be any hotter" is completely unfounded in reality.

[NamTaf]

Reading a bit more into this, I'm still not sure whether the tunnels are actually continuing to meaningfully increase absent external changes to the system. Is it at a steady-state heat flux between the inputs (passenger, vehicles, infra) and output (into the surrounding earth), or is the surrounding earth still not effectively saturated?

I know heat inside the tunnels fluctuates with time of year, but I can't tell if year-on-year the tunnels are getting e.g. 1xx% hotter and, critically, what the causes are (more tph will obviously, global warming will, more pax will).