Abrannan's description of the basic gameplay is a good one. Really did play out alot like StarFleet Battles.
There were many scenario options available. The idea was that in this sorta post-apocolyptic world (Think Mel Gibson's
Road Warrior sorta) people armed their vehicles to defend against maurading gangs and just everyday road rage filled drivers. This carried over to the sport of Demolition Derby when (I forget his name and don't have my sourcebooks here) a guy mounted a surplus .50 caliber machine gun to his car. The sport of AutoDuelling was born. Typical scenario setups were either an AutoDuel layout in a large arena, or an on-the-road setup.
You'd typically be given vehicle requirements and an amount of money to spend on your vehicle. Say you were competing in an Arena Duel. You may be limited to mid-sized cars and under with $35,000 to spend. I always felt that designing the car was the most fun part.

You had an almost limitless amount of decisions to make. Body style, frame, suspension, engine, accessories, tires, offensive weaponery, defensive weaponery, targeting & driving aids, personal body armor, the list goes on and on.
If you wanted to get really in-depth there were some RPG elements put forth so that you could play a continuing character. A group I gamed with did that for a while. I had a
Smokey and the Bandit type pair that included a long-haul trucker with an escort in a sports car. We'd fight on long stretches of straight & curved highway with scattered debris and oncoming traffic and whatnot. Fending off hijackers and such.
While there doesn't seem to be much in the way of the original source material available on the net, many of the issues of AutoDuel Quarterly have been HTMLized. (Looks like the issue that I was doing never got finished by anyone else either. Guess I should get it done.

) This was the quartely magazine which included rules updates, scenarios, car designs, fiction, etc. A good place to get a feel for the game.
http://www.sjgames.com/car-wars/adq/I may hafta see if there's gonna be a big game going on at Gen-Con this year.