Development of a new modified TSRST test to measure the thermal stress of asphalt supporting layer in the slab track system

•A modified TSRST test method was developed for asphalt supporting layer in the slab track system.•The HDPE-AC specimen was newly designed to realize automatic loading of the extra thermal load.•The development process of thermal stress in asphalt supporting layer was experimentally studied.•The effects of extra thermal load on cracking resistance of two asphalt mixtures were investigated.