It reminds me of Heinlein's moving highways.
Have to agree with Vert, it only moves the queue around. Maybe you travel 100 MPH once on it, but you are going to wait an hour to get on it. In fact I cannot see how it would not net out to MUCH more time consuming from point to point. And there does not appear to be any hope for a solution if the exit you want is already backed up - you WILL go on forward possibly for many many miles. Alternately of course, the entire glideway could stop until Every ramp has at least one slot.
Combine this with the sky high death toll caused by the tiniest computer glitch, and the 5000 King's ransoms to build it into a single city...
Sorry, honestly it looks like one of the most impractical ideas I've ever seen.
Edit: In Heinlein's system the highway was actually several (eight?) belts that got progressively faster as you worked to the center. Thus you had some better queuing on and off. But still there is no solution for over crowding.