AbstractTo illustrate the influence of differential settlement along the lateral direction of subgrade on the dynamic performance of a high-speed vehicle system, based on the vehicle–track coupling dynamic theory and finite-element method, a vehicle–track–subgrade spatial coupling dynamic model considering the lateral mechanical characteristics of the vehicle system is established, and the dynamic performance of the vehicle system under different lateral differential settlement parameters (amplitude/wavelength) of subgrade on one side and both sides and the vehicle speeds are studied. The study reveals the following. The vehicle dynamic response under the lateral differential settlement of subgrade on both sides is generally greater than that under the lateral differential settlement of subgrade on one side, and the difference becomes more obvious with increases in the lateral differential settlement amplitude. However, there is little difference between the two lateral differential settlement modes on the car body lateral acceleration. The wheel/rail vertical force of the left rail (with large settlement amplitude) is greater than that of the right rail (with small settlement amplitude), while the wheel/rail lateral force of the right rail is greater than that of the left rail. The dynamic response of the vehicle system increases with increases in the lateral differential settlement amplitude; the dynamic response of the vehicle system increases noticeably when the amplitude of lateral differential settlement exceeds 25 mm. The lateral differential settlement wavelength is inversely proportional to the dynamic response of the vehicle system, and the wavelength range 5–15 m has the greatest impact on the dynamics of the vehicle system. The vehicle driving speed is directly proportional to the vehicle system dynamic response, and the vehicle system dynamic response increases significantly when the driving speed exceeds 250 km/h.