I searched on google for “heat kink” and all it returns are references to the Metro rail system. It seems like this would be a noticable problem in many other places, but it doesn’t seem to be a problem anywhere else. Perhaps they need new rail engineers that have dealt with the sun before.
Try googling warped rails, heat warping, derailments, etc.
“It seems like this would be a noticable problem in many other places...”
This has never happened in NYC, so far as I can remember. There are miles and miles of outside tracks in NY, and while there have been problems in the winter with switches freezing, I don’t ever remember a derailment caused by heat.