“…Raw data type: it is observed that 70% of studies used image-type raw data for the deep learning models. Nevertheless, acoustic emission signals [65,71,100,103,108] , defectogram [96,109] , speed accelerations [98] , concatenated vector of curve and numbers [101] , current signal [89] , maintenance records [80,99] , synthetic data from generative model [63] , time-frequency measurement data [82] , time-series [60] , geometry data [87] , and vibration signal [119] could all be possible input data sources as well. Purpose of study: it is observed that detection, classification, and/or localizing rail surface defects including various components (rail, insulator, valves, fasteners, switches, track intrusions, etc.)…”