Abstract: China boasts a vast territory characterized by diverse climate types, resulting in significant variations in temperature and humidity across different regions. The wheel-rail contact condition of subway vehicles during long-term operation is closely linked to the environment. Occasionally, subway vehicles experience abnormal lateral shaking, which severely impacts vehicle performance and passenger comfort. To obtain a deeper understanding of the mechanisms behind this lateral shaking phenomenon and its relationship with the environment, this study focuses on subway vehicles operating on ground or elevated bridges in semi-open environments, while considering different temperature and humidity conditions. Firstly, the year-round temperature and humidity fluctuations in four cities across various regions of China are investigated. Subsequently, a transverse dynamics model of subway vehicles is established, taking into account the operating conditions influenced by temperature and humidity. Three classical creep theories are selected based on the varying temperature and humidity conditions in the model. The impact of temperature and humidity on the lateral stability of vehicles under different levels of equivalent conicity during service is studied. Additionally, the lateral ride stability of subway vehicles in typical cities with diverse climates was analyzed. Finally, the causes of lateral abnormal shaking are discussed, considering the three influencing factors: temperature and humidity, equivalent conicity, and velocity. The results indicate that the occurrence of lateral abnormal shaking of subway vehicles under changing ambient temperature and humidity conditions may be attributed to the substantial creep force between the wheel-rail interface and the frequent transition between stick and slip friction states. Furthermore, in extremely cold areas, the likelihood of lateral abnormal shaking increases, especially when combined with high conicity and high running speeds. Conversely, such occurrences are less likely in hot and humid regions. To address the issue of lateral abnormal shaking, improvements in the wheel and rail lubrication, effective management of equivalent taper, and appropriate deceleration in sections prone to abnormal shaking are recommended. The work provides valuable insights into understanding the causes of lateral abnormal shaking of subway vehicles, particularly in extremely cold regions.

Key words: subway vehicles, temperature and humidity, running stability, lateral abnormal shaking, equivalent conicity