First of all, CWR isn't heated to the maximum expected temperature when installed. The rail will expand and contract some in cross section before expanding length-wise. However, CWR must be installed at a specific temperature, which is determined by the normal highs and normal lows for that area. the installation temperature (IT) is VERY important. If it is colder than the IT, you heat the rail with special portable rail heaters. If it is hotter than the IT, you can cool the rail with chilled water sprayed on the rail. Special hi-rail trucks are equipped to do this.

The problem comes from unusually high temperatures (sun kinks) or unusually low temperatures (broken rails, pull aparts). This is caused by either improper installation or post installation track-work creating sections of rail that are stretched out or bunched up. The use of rail distressing equipment, which vibrates the track to even it out is very helpful.