A new fast moving sidewalk is undergoing field trials in Paris. It transports walkers at 9kph (5.5mph), about twice as fast as existing moving sidewalks.

Larry Niven wrote a lot about what he called 'slidewalks.' He envisioned as many as 10 sliding floor tracks edge to edge next to each other, with each one to the left moving a few mph faster than its neighbor. That way someone could step from a stop onto the first 3mph moving sidewalk, then make one more 3mph faster transition, stepping to the next one, until they were going 30mph (or faster) in the 'fast lane', emulating how multi-lane freeways work. People could get on and off wherever they chose, and there would never be a situation where someone would accidentally accelerate or decelerate drastically.

The Paris system is much more like a traditional moving sidewalk, but uses a 'ramp up' section to accelerate passengers to the fast speed, and a ramp-down at the end to bring them to a halt. the animation provided in the article does a great job of showing how this works. It's more sophisticated than just a shorter sidewalk of intermediate speed.

It'll be interesting to see where this goes. Personally, I still see the biggest problem being the point-to-point nature of these sidewalks, making them useful for simple high-traffic routes, but not so useful for, say, getting from one gate to another in an airport, or navigating a city, because with the current design you'd have to get on and off the system at every possible stop.