Senescence and capacity are half the problem; the other half is that the teams (public as well as private) maintaining these systems don't have the logistics ca

Senescence and capacity are half the problem; the other half is that the teams (public as well as private) maintaining these systems don't have the logistics capacity to 'repair in place', to make substantial fixes without taking a train line completely offline. (And I assume municipalities aren't offering to pay extra for that service).