Ok
I have no idea what the minimum separation is on the busway but I suspect that they could easily double or treble capacity by adding more buses.
The same as any other road, so effectively "a safe distance". I have seen vehicles following each other down the busway on plenty of occasions.
I believe the speed limit for the busway is 55mph, the Highway Code stopping distance for 60mph is 73m/240ft. Though the changing speed between 55mph and 30mph when they cross public highways probably stops you having a steady stream of buses following each other at minimum distance.
I suspect the limiting factor on the northern busway will ultimately be like on a tram line - the traffic light phasing at some of the road crossings on the route. But yes, current usage is well short of that being a problem (the bigger problem is dealing with all the buses in the centre of Cambridge).
On the southern busway, the "single line" section on approach to Trumpington Park and Ride will be the determinant of capacity (and the single deck restriction)
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I believe the speed limit for the busway is 55mph, the Highway Code stopping distance for 60mph is 73m/240ft. Though the changing speed between 55mph and 30mph when they cross public highways probably stops you having a steady stream of buses following each other at minimum distance.
I recall there are rules where a bus approaching an occupied stop must wait a certain distance behind (presumably it's quite easy to misjudge braking on approach)