I am writing a sports simulation game in which the simulated players will interact physically with each other (i.e. tackle, push, bump...) as well as do individual actions such as changing direction of motion quickly in response to a changing game state.
At the moment all movement occurs with no inertia and infinite acceleration (so each step of the game loop the player can move at their top speed in whatever direction they want, regardless of their current motion). This has been sufficient to develop the main parts of the player AI, but it's time to get a little more realistic. The game has a cartoony look and feel so it doesn't need to be perfectly realistic, but player movement and interaction should give a semblance of reality.
So, how could human movement be summarized in a few key restrictions? I've toyed around with setting maximum acceleration and turning rates, as well as a momentum/inertia model for dealing with player collisions, but the game ends up looking like it's played by a bunch of bumper cars, rather than people (i.e. these restrictions and collision model describe cars on a slippery surface, not bipeds).