Hey there,
If I understand correctly, you are talking about the movement of the vehicle to impact the player when they stand on it.
Depending on what tools you use to develop your project, the main idea is to keep track of how many objects are on top of the vehicle. When the player steps on it, add that player to that list.
Now when updating the vehicle’s motion, apply the same amount of offset to any object on that list. When an object gets of the vehicle (like when the player jumps) remove them from the list, until they step on the vehicle again.
This explanation is a bit vague because I’m not sure what tools you use, but hope it helps give you the right ideas.