Continuous welded rails (CWRs) have significantly strengthened the railway tracks by eliminating rail joints between rails. However, as the ambient temperature changes during a year from cold winter to extremely hot summer, high thermal stresses exist and change within the CWR. In some circumstances, it may cause catastrophic disasters such as track buckling, broken rails, and/or derailment. To ensure the CWR track is in stable, longitudinal stress (neutral temperature of CWR) measurement is the most important of the CWR track maintenance. Using the non-destructive method to measure the longitudinal thermal stress in CWR tracks is one of the effort directions for railway track engineers and researches for decades. Within Australia, in the last decade, three types of non-destructive technologies have been approved by the railway infrastructure authorities for neutral temperature measurement. In this paper, the physical theories and technical background of these three technologies are introduced and discussed. In addition, the advantages and limitations of these technologies are discussed based on the experiences that are obtained by using them.
