• A novel 3D human-seat-vehicle-track coupling model was developed to accurately assess high-speed train ride comfort, incorporating multi-axis human body dynamics.
• Floor acceleration alone underestimates passenger discomfort; seat and backrest connection points exhibit higher vibration amplitudes in human-sensitive frequency ranges.
• Track geometric irregularities and train meeting conditions significantly degrade ride comfort, especially when excitation frequencies approach the natural frequency of the human-seat-vehicle system.
• Transient aerodynamic forces during train meetings induce car body roll and lateral motion at 2 Hz, further reducing passenger comfort.