Overall, the single rider really only "works" at TT. That line is constantly moving since the vehicles hold such an odd amount. Doesn't work quite as nicely at EE or RnRc.
The "success" of the Single Rider lines is very much dependent on the CM working the grouper position at the head of the line, and to a lesser extent the Guests in the Single Rider line themselves. (An inattentive Single Rider who's next in the line can cause the whole thing to slow down if they're not paying attention when they're called on)
During my last trip, I rode EE multiple times over multiple days, and saw mostly so-so groupers but one excellent grouper. She was definitely a take-charge kind of person who knew what needed to be done to keep all the lines moving. It was actually kinda cool to stand there and watch her work. Kind of a ballet, really. (Just without the tutu and jumping) And every time there was an odd number of Guests coming from the main queue came the call of "Single Rider!". That one position is managing 4 things all at once: Feeding the correct number of Guests down toward the front of the train where the front grouper deals with them, grouping Guests into the rear cars, inserting Singles where appropriate, and directing people who ask for the front row into the Front Row Holding Queue adjacent to the Singles Line. And then when she completes one train, she grabs the next people from the Front Row Queue, sends them to the front and starts the whole process over again. Definitely takes talent.
Oh, and if a wheelchair Guest comes along, they need to be directed to the handicap-accessible Row 17.
Compare that to Test Track and RnRC. At Test Track the grouper just loads 8 rows of 3, using Single Riders for all odd groupings. And over at RnRC it's a similar situation as EE, but there's only 12 rows instead of EE's 17. I also believe the dispatch interval is faster on EE than on RnRC.
So EE groups 34 people at a time, whereas TT and RnRC both group 24 people at a time. (And in slower periods TT only uses three load zones, making it 18 people at a time).
-Rob