Non-stationary random vibrations gained increasing interest in vibration testing. Often, a changepoint detection procedure handles the decomposition of Road vehicle vibrations (RVV) when analysing the recorded series. Unfortunately, only subjective justifications support the proposed methods, and mainly the validation of the non-stationarity of simulated signals is concerned. Thus, if a detector is inherent to the procedure, it is also recommended to calibrate it. The current paper concerns the Receiver operating characteristics (ROC) of a CUSUM-type algorithm and supplies contextual support by Segment length distributions (SLD).