Instead of empty warehouses, cardboard cutouts, and heat lamps (like you'd see at Test Track), in RSR you will find full-sized CARS cars that wink and blink and move and talk - animatronics. You basically drive outside town and then into town while on the ride (yes, the town is also built just outside the ride, but you accept the fakeness of that), enduring a few adventures and seeing familiar friends.
Then you meet up with the car in front of you (or maybe the one behind you) and have a friendly race. It's a fun ending that offers thrills without needing to take up too much real estate (which is at a premium here in Anaheim).
My overall verdict: this ride is great. Much better than Test Track. Maybe that's because I like dark rides and animatronics in general, but I rather suspect it's just a better ride, better realized, and better themed. Definitely worth the long wait in line (FastPass is better if you get there at park opening to snag one. And single-rider line is not a bad option, either).
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Kevin Yee is the author of numerous independent Disney books, including the popular Walt Disney World Earbook series and Walt Disney World Hidden History.