I introduced this game to my office a few years ago and we have been playing it during EVERY lunch hour since. To keep the game fresh and exciting, we have come up with some variants:
1. The game is much riskier if you permit drawing from the discard pile. You are forced to keep fixes in your hand (if another player has a STOP, you shouldn't discard a GO even if you have the right-of-way). You can also draw mileage from the discard pile if you are not having any luck with your draws.
2. We had a second, worn deck and added the 'super cards' and four '25 mile' cards to our deck. This way, there are two of each super cards. If you play the right-of-way, you could lose it if someone else plays the second one. Having one clean and one dirty (or two different card backs) adds to the fun because someone with a super could play it unnecessarily to be able to draw a dirty card at the top of the deck, in hopes that it is also a super. BUT it could be just a 25 mile card! We love this alternate! Only ONE super card is allowed in play so if you have one in play and another player plays the same super card, you must discard yours (and lose its benefits).
3. When playing with 5 players, we have come up with some interesting rules - otherwise, playing 5 is a boring game with a lot of stopped players. It is almost impossible to get far with 5 players:
A. 'share' all super cards (right-of-way, driving ace, extra tank and puncture proof) with the player to the left. This works out very well and is a lot of fun. You play a 'stop' on the player to your right in hopes he coupe forre's the card which would give him and you both the right-of-way.
B. We have two discard piles - one for mileage and one for non-mileage. That way, you can either draw a card from the pile, or draw from either discard pile.
C. Each time you play a GO card, you have the option to play a mileage card at the same time (but you don't get to draw so your hand goes down by a card).
D. Only one 'red' card is allowed per player. If you have a 'speed limit' card, you can put down as many 25's and 50's as you want because you can't be stopped by another card.
E. Game is to 500 miles, extension is to 700 (only one 200 mile card)
E. The final special rule for five-play: If you are stopped with a red card, and you fix it, you get to go again (draw and play). So if you have a 'stop', you can play a go (and play a free mileage- see C. above) and then you draw again and play. This does not apply if you play a GO on a previously fixed tire or gas or repair - only if you fix a 'red card' do you get a second play.
Give these a try and let me know what you think!