• Long-term tracking of CRTSⅢ slab ballastless track reveals that irregularities with wavelengths longer than 10 m show larger amplitudes, faster evolution, and linear growth, primarily impacting vehicle stability.
• Shorter-wavelength irregularities (<10 m) exhibit minimal evolution and mainly affect vehicle safety, highlighting the need for wavelength-specific management.
• The arching of 32 m simply-supported beam bridges induces periodic irregularities with evolution rates significantly higher than other wavelengths, requiring focused monitoring.
• Recommended classified limits for track irregularity are proposed based on limit-exceeding probability of safety and stability indexes, aiding maintenance strategies for high-speed railways.