For the worn state of the wheel, metro vehicles often suffer a serious carbody swaying issue, which causes the lateral stability of the vehicle to exceed the limit and affects the ride comfort. An experimental test was carried out on this investigation to study the carbody swaying of the metro vehicle. The field results show that the vehicle system vibrates at around 2.5 Hz in the lateral direction, which leads to the low-frequency swaying on the carbody. In order to explore the formation mechanism of the carbody low-frequency swaying and its relationship with the geometry matching of wheel-rail contact, measured rail and wheel profiles are employed to present a comparative analysis with respect to the initial contact geometry. A multibody dynamic railway vehicle system is established further. Time-domain simulations state that the 2.5 Hz vibration on the carbody belongs to the natural frequency of the vehicle, and the amplitude is larger for the measured wheels than that of the standard wheel profiles. By using the root-locus method, it can be determined that the 2.5 Hz vibration corresponds to the upper swaying mode of the carbody. With the increase in the wheel-rail equivalent conicity, the hunting frequency of bogie increases gradually, which converts frequency with the upper swaying frequency of carbody and leads to carbody low-frequency swaying.

In the operation process of metro, abnormal vibration occurs at the axlebox, and causing structure damage on some components, so the dynamic test was carried out. The result shows that the abnormal vertical vibration about 80–120 Hz is the direct cause in the vehicle operation, and it relates to the type of track bed. According to the track and vehicle, two finite element vertical models of vehicle-track coupling system were established. It determines that the first order vertical bending mode of rail in the coupling system is the excitation source of the abnormal vibration through frequency analysis. And this mode is mainly related to the vertical stiffness of fastener and rubber cushion under short sleeper, which will increase with these stiffness values. Finally, through actual stiffness measurement, it sees that the fastener vertical stiffness values in ordinary track section are mostly reduced to the frequency range corresponding to the first vertical bending mode of rail in the coupling system, which is the cause of abnormal vibration. Therefore, by adjusting the fastener vertical stiffness or adopting the track type to be a damping track bed, the impact of vibration near 80–120 Hz can be reduced, so as to avoid the structural failure of vehicle components and ensure the operation safety of metro vehicles.

Wheel polygonal wear of metro deteriorates the vibration environment of the vehicle system, potentially leading to resonance-induced fatigue failure of components. This poses serious risks to operational safety and increases maintenance costs. To address the adverse effects of wheel polygonal wear, dynamic tracking tests and numerical simulations were conducted. The modal analysis focused on the vehicle–track coupling system, incorporating various track structures to explore the formation mechanisms and key influencing factors of polygonization. Test results revealed dominant polygonal wear patterns of the seventh to ninth order, inducing forced vibrations in the 50–70 Hz frequency range. These frequencies closely match the P2 resonance frequency generated by wheel–rail interaction. When vehicle–track coupling is considered, the track’s frequency response shows multiple peaks within this range, indicating susceptibility to resonance excitation. Additionally, rail joint irregularities act as geometric excitation sources that trigger polygonal development, while the P2 force resonance mode plays a critical role in its amplification.