The vehicle is made such that you can walk around in it freely. Detailed colliders allow for good interaction. See screenshot.

This is low poly vehicle template, for simple game or testing purposes. 

This was originally a popular mod I made for a low poly game, but I've refurbished it to be the asset you see here.* The colliders are set up to allow a standard 2 meter character to interact easily with it. 

If you are developing a vehicle system, or using an existing one, this has the necessary parts to interact with, and make a minimally functioning vehicle.

*Although this was originally a mod, all parts on this asset are original and not a part of the game it interacted with.