## 4 Conclusions  
In this study, the effect of the IVS on the dynamic performance of a high-speed train is analyzed by creating force elements to simulate the mechanical properties of the suspension devices between vehicles. A multibody model of a CRH2 high-speed train considering the IVS is constructed. Considering different crosswind wind speeds and different curved lines, the safe driving speed is determined and dynamic differences between the two cases by considering the IVS and fixed connection when the curve passes in acceleration and deceleration conditions under crosswinds are analyzed. The main conclusions can be summarized as follows. Figure 17: Comparison of lateral vibration acceleration of car body when accelerating through the curved track. (**a**) The head car. (**b**) The middle car. (**c**) The tail car. Figure 18: Comparison of the car bodies’ motion angles in two cases during acceleration. 1. The safety of the train is sensitive to the radius of the curve track when the curve passes under crosswinds. When the vehicle speed is less than 250 km/h, the unloading factor changes little with increasing radius. When the vehicle speed is 250-350 km/h, the maximum value of the unloading factor reduces with increasing radius. However, the reduction will be little when the radius exceeds 7000 m. Moreover, the safe speed of the train should be less than 250 km/h when the wind speed exceeds 25 m/s. 2. Compared with fixed connections, taking the IVS into account will reduce the critical safety speed at the same radius. This reflects more realistic train dynamics. The safe speed decreases by 18 km/h, 9 km/h, and 14 km/h at a wind speed of 25 m/s at the radius of 4500 m, 7000 m, and 9000 m, respectively. The difference in safe speed between the two cases is very small when the wind speed is 30 m/s. Consequently, the true safe speed limit for CRH2 trains should be lower than the current recommended values. 3. Considering the IVS will reduce the unloading factor when passing a curve during deceleration under crosswinds. The BF bogie has the greatest reduction, of which the unloading factor is reduced by 3.38% and the derailment coefficient is reduced by 5.56%. Furthermore, the maximum value of lateral acceleration in the middle car is reduced by 49%. For the car-body motion angle, the head car and tail car are insensitive, but the pitch angle of the middle car is increased by 8.11% and the yaw angle is reduced by 14%. Taking into account the IVS, vibrations in the train car are reduced during operation. The level of reduction varies from carriage to carriage. 4. Considering the IVS will increase the unloading factor when passing a curve during acceleration under crosswinds. The BF bogie has the greatest increase, of which the unloading factor increases by 7.27%. The derailment coefficient of FB, MB, and BB bogies increases by 4.51%, 3.76% and 6.94%, respectively. Moreover, the maximum value of the lateral acceleration of the head car when driving out of the spiral transition curve track is reduced by 55.13%, and the middle car is also reduced by 32.26% when driving out of the circle track. However, the maximum value of the lateral acceleration of the tail car increases by 68.17% when entering the spiral transition curve track. These results suggest that considering the IVS effectively reduces the maximum value of the lateral acceleration of the vehicle when passing the transition areas of the curved track, especially for the middle car. In conclusion, considering the IVS will result in lower safe speeds than fixed connections but reflect more realistic and credible train dynamics. However, due to the workload, we did not consider the effect of wind speed variation and only used constant forces to simulate the traction and braking forces. In the future, the effect of wind speed variation and more realistic traction and braking forces will be considered to further deepen the study.