One of my favorite Disney exhibits of all time was a scale Imagineering model of Space Mountain with each turn marked with its speed. As I recall the maximum was about 25 mph / 40 kph, which is considered lame by coaster standards, but results in a thrilling ride due to the design. Unfortunately they screwed with the all-lefts setup and now it's merely very good.
I was riding the WEDWay People Mover in Florida, which goes through Space Mountain, and the lights happened to be on. Very cool to see how compact the whole thing is.