Surprised no one has answer this!
Allears.net has great write-ups on all the rides.
http://allears.net/tp/mgm/tsm.htm
The car seats 4 people back to back. 2 on one side 2 on th other side. Sometimes I have seen two adults with a small child in the middle or 1 adult and 2 children. But for the most part 2 adults.