Vehicle Stats

How do you get per-vehicle stats? The players site gives, for example, score earned while on a Flash, or amount of time spent in a Liberator. I assume this is accesible through the API, but I can't figure out how to do it. I've tried using characters_weapon_stat, resolving with vehicle, and adding up stats for each weapon on a specific vehicle, but it doesn't take into account score accumulated while in the drivers seat or as a passenger.

Any ideas?