that thermite-weld fatigue resistance can be significantly and reliably increased by improving the shape of the weld-toe in the web-base fillet and rail-base regions of the weld and by suppressing common weld-toe defects found there. Laboratory 4-point bending fatigue tests were carried out on five series of thermite welds: three series had a standard external shape currently in use and two series had an improved shape developed in this study. Test laboratory results show that improved welds have a fatigue life approximately 2 times that of standard welds.