What if every car wanted to turn on you, no matter what it takes? What if every single car would disregard its owner's commands and go on a violent rampage that would only stop once they were immobilized by either being turned upside-down or thrown in the ocean? Well, now you can find out what I mean by all these cheesy sentences.
Handling.dat files for GTAIV. Both the vanilla, unaltered, versions and the carmageddon'd versions included. Drop it right into your main GTAIV folder.