Kolkata Metro: The only Metro of IR. কলকাতা মেট্রো : তিলোত্তমার জীবন রেখা ।। - PPG

This video is taken on Kushtagi - Gangavathi road. The train is moving from Gangavathi station towards Koppal.
I took a pic here too last July /blog/post/3674316 last pic.

---

The rails are flexible. As long as they are fastened properly and the train moves at a uniform pace, there won't be any problem in going even through sharp curves.

---

Flexible? But flexible enough for sharp curves?

---

Yes. The rails are very flexible. That is why steel rails are used for laying tracks. They are flexible enough that they can be bent to lay curved sections of track, but are strong enough to bear the load of the train.
You can see the rails curving in a similar freight train in the following video. Note how sharp the curve is and how the rails too curve accordingly.

---