Basically, the PHM system presented in figure 1 encompasses two rugged RotoSense wireless sensor modules packaged for standard mounting on the wheels of a rail car or locomotive axle, one Sentinel Gateway wireless data collection hub, to collect and store RotoSense data and the RailSafe Toolbox, including the necessary software packages to set up and operate the RotoSense sensors and the Sentinel Gateway, and to extract and display diagnostic and prognostic information based on RotoSense data.The sensors are mounted on each end of an axle, right where the wheels and track meet, the three-dimensioned microelectromechanical systems (MEMS) based instruments continuously capture wheel and track vibration data with maximum sensitivity. The data are analysed using the RailSafe Toolbox, including the Adaptive Remaining Useful Life Estimator™ (ARULE™), which has been proven in aerospace and industrial condition-based maintenance (CBM) systems.The RotoSense sensors are easy to install and use, and one on-board Sentinel Gateway™ Internet of Things (IoT)-enabled wireless data collection hub can receive and store data from 1,440 hours of operation across all the sensors on a car. The data can be compressed and uploaded to the cloud through an optional cellular connection, sent via Ethernet to another on- board data storage/processing device, or transferred manually for off-board analytics. The RailSafe toolbox can be installed on the train to alert operators to dangerous conditions in real time. The RailSafe Toolbox produces graphics depicting key performance parameters such as track or wheel state of health (SoH) and remaining useful life (RUL) as shown the figure 2.