(To continue the hijack.)
I read about how this 'snakiness' is prevented in welded railtrack. It is installed stretched so temperature changes just alter the stress in the rail. Of course if the temperature goes too high the expansion overcomes the stretch and the raill buckles. Conversely, if it gets too cold the contraction imposes too much stress and the rail breaks. Both of which do happen but not frequently and the failures are normally found before a 280km/h train tries to go whistling by.