If the line for Test Track is long, and your party doesn’t mind being separated (or not being able to fully design a car), go through the single rider line. You will all go through the pre show together, and when it is time to get on a car, they fill you in one by one into the empty 3rd seat when 2 people sit. Sitting in different cars (usually one behind the other) was a small price to pay for this time-saver! And sometimes, two of you will even end up in the same car!