Objective When heavy-haul trains apply brakes at grade change points, the sudden change in gradient resistance and the asynchronous braking of vehicles will induce significant longitudinal impulse. Suppressing the longitudinal impulse during the train braking process is of great significance for ensuring train operational safety.

Method A multi-rigid-body particle longitudinal dynamics model is established. Taking a '1+1+1' marshaled combined heavy-haul train as the research object, the influencing law of grade slope, the distribution ratio of electric braking force among locomotives at different positions, and the asynchronous application modes of electric braking force on the train longitudinal impulse under the condition of electro-pneumatic combined braking at grade change points are analyzed.

Result & Conclusion  The greater the grade slope, the more severe the train's longitudinal impulse. When combined braking is applied at a concave grade change point from a downgrade to a level track, the maximum coupler force is predominantly compressive, reaching up to −2019.48 kN. For the '1+1+1' marshalling, when the middle and rear distributed locomotives are allocated 1/3 and 2/3 of the electric braking force respectively, the maximum coupler force is −937.00 kN. Compared to the scheme of average distribution among all locomotives, the maximum coupler force is reduced by 15.7 %, and the braking distance increases by only 10.93 m. Under the same electric braking distribution ratio, reducing the electric braking force distribution of the master locomotive and selecting an appropriate electric braking ratio for the middle and rear distributed locomotives can effectively alleviate the longitudinal impulse of the train. Under the premise that the braking distance remains basically unchanged, delaying the application time of the electric braking force for the master and rear distributed locomotives can moderately alleviate the train longitudinal impulse.