I read this in the early nineties in an anthology UK.
There was a planet the male protagonist arrived at. It was famed in the local star system due to the speed of it's technological advances.
Apart from static spaceports, harbours and ports and suchlike infrastructure all the cities (I think there was only three or four) were mobile.
Not forever moving, every few months they packed up and migrated a few miles to a fresh area to follow this speed-up radiation. This enabled the fast tech stuff.
New arrivals had to acclimatise because they saw the inhabitants as blurred fast figures who did high pitched squeaking to communicate. The city people saw newbies as very slow and clumsy but within a couple of days they fitted right in.
One phrase constantly used was "The berries was bad" whenever a city dweller slowed down a touch, if more and more acted like this then a decision is taken to move the city to a new locale.
I can't remember much about the adventures the visitor had, that berries phrase popped up in my memory and is now tormenting me.