A review of techniques for measurement of forces and neutral temperatures in railway track

Track failures in the form of thermally induced buckling events or rail breakages on continuously welded rails (CWRs) have long posed challenges for the rail industry. These issues arise because CWRs cannot freely expand or contract as rail temperatures fluctuate during operation, resulting in compressive or tensile stresses. As temperature variations increase, these stresses can lead to rail buckling under compression or separation under tension. Buckling, in particular, poses a serious threat, as it is often associated with derailments, carrying substantial social (rail safety, public perception) and economic (track downtime, damage to freight, rolling stock, and infrastructure) consequences. For this reason, understanding the thermal stress state or neutral rail temperature (NRT) of installed track is critical for rail network owners and operators. This knowledge enables more precise planning of maintenance, targeted rail replacement, and monitoring of high-risk areas. Consequently, there is growing demand for in-situ, non-destructive methods to measure NRT. This paper reviews existing methods for measuring NRT, encompassing approaches developed from the 1960s to the present. Each method is critically evaluated, with the findings summarized in a table that outlines their operational principles, limitations, reported accuracy, and current technology readiness level.