I might get some flak for saying this, but as far as when the most acceleration for any mass occurs, it is during the infinitesimally (spelling?) small period of time in which the car changes from stationary to moving. If I'm wrong, the engineers and such of this discussion please correct me and tell me where I'm wrong and why. It's only a self-arrived to conclusion of my own I've had for some time and now I have the chance to see if I'm correct or not, as well it applies to the discussion.