At its most basic, the drive train is made out of metal, and therefore acts like a spring. If we ignore the gearbox and clutch for a tick, we imagine the energy the wheel rotation has (and the inertia of the vehicle, etc) as one end of the spring, and the energy the engine is producing as the other end of the spring.
Hooke's spring law then tells us how much engine force gets applied to the wheels, and vice versa. If the spring extension length gets too high, you can make the clutch slip, or the engine throw a piston, or one or more tyres can overcome friction (depending on how elaborate your diff is), or whatever you feel needs to happen.
That way, the accelerator is just another force acting on one end of the spring.
One problem though, is that this needs to be a *very* stiff spring. Or possibly two springs. Hope that helps :-)