Most people spend each day trying to stay alive, and those with cars spend a lot of that time trying to keep those cars in prime shape. But, racing has been a time-honored tradition, dating back to when we rode animals. It's a way to garner street prestige, make easy cash... and a good way to get yourself killed.
A race is usually more than just two cars roaring down a strip of road. There is showing off the car beforehand, "talking smack" on the other drivers, boosting yourself and lowering them... a street race is as much a social hierarchy behavior as it is a test of skill. Some races, similar to the chariot races of Roman times, can be violent, brutal, and lethal. Some groupings of racers prefer to leave out dirty tactics to pit pure driving skill against pure driving skill, and others embrace it as part of the racing experience.
In all cases, each race is different. Typically, the cars will start out evenly. The rules, race course, and all other elements will usually be either stated or assumed to be understood. A signal will be given... and the race starts.
All racers roll a Drive Test. Any who get 15+ get a free action (not a free turn, just one action) before the others. This, typically, is used to accelerate forward.
All racers act simultaneously, although Initiative (Agility/Level/Luck) may be rolled for simplicity for a GM mediating the race and to keep track of rounds.
All other driving rules apply to the race. Distance traveled is tallied at the end of each round. For acceleration, treat distance traveled based on the speed after all acceleration takes place. Each round lasts a little less than 4 seconds. To calculate distance in feet traveled, multiply the current speed by 5.5 to get the number of feet traveled in 1 round.
Typically, the winner of a race is the car that crosses the finish point first, or the last car remaining in the race. If two cars cross the finish line in the same round, have each driver make a Drive Test Whoever wins this drive test crosses the finish line by a split second. Reroll ties.