Temperature monitoring of axle bearings and brakes on passenger and freight trains is an important factor for the reduction of downtimes or maintenance expenses. Measurement requires contactless methods. This is typically done by sensors which are mounted in the track to measure thermal radiation of the passing chassis. The data is subsequently analysed by mathematical methods. In a long-standing and successful cooperation with the company Progress Rail Inspection and Information Systems (PRIIS), we are developing the software for the chassis monitoring sleeper (FUES). The software analyses radiation profiles, detects overheating components, and transmits results to registration centers.