Track is like road, it has to be maintained and once in a while replaced. It also helps if it was built right to begin with.Time-lapse movies shows trains that are actually moving very slowly and carefully. It is amazing how reliable 1800's railroad technology still is today, even when tracks are not properly maintained. Buckling of continuous steel tracks happens when temperatures change throughout the seasons, causing expansion and contraction of the tracks. Proper tracks are laid in sections with breaks between the sections so that expansion has room to occur. When expansion has this room, there is no buckling of the tracks. This applies also to some pavements and roads for cars and trucks.