“…In the former category, sensors are usually mounted on rails (Yue et al., 2016), sleepers (Le Pen et al., 2016), ballast (Liu et al., 2021), or concrete slabs (Zhang et al., 2021) to measure their dynamic response under train passage and to support the identification of track properties. However, these techniques are cost‐prohibitive for large‐scale infrastructure monitoring, so they are usually applied at hot spots, such as joints (Yang et al., 2018) and crossings (Boogaard et al., 2018; Shen et al., 2019). In the category of train‐borne measurements, sensors are mounted on trains, such as on their axle boxes or bogie frames, to detect anomalies in railway tracks (Bocciolone et al., 2007; Li et al., 2022; Salvador et al., 2016).…”