I notice people that want to switch positions in a warthog manually get out and walk to the spot that they want. I don’t blame them. That’s how it was in past Halo games. But in Halo 5 you can DOUBLE TAP A BUTTON to switch positions within a vehicle. Example: to switch between driver and gunner.
Due note this is for the default control scheme. That would be the jump and clamber button I would assume for other control schemes.