I forgot the most important point. The two (or more) units of hastati or other infantry should be ON TOP of each other. Yes, that's right, crowded into the same positoin .This seems to stop the chariot in their tracks. That will seem incredibly counter intuitive for an mtw player (given the severe crowding penalties), especially since chariots have an aoe attack. But having a thick mass of infantry seems to stop the chariots cold.

Once they're mired in the mass with 20 guys attacking them at once, they die rather quickly.

You can usually rout the chariots w/ minimal casualties using this method (assuming the chariots run directly into the mass).

Still very hard to get chariot archers to do this, however, without an elaborately staged trap.