story identification - Novelette - mobile cities follow 'fast' radiation

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.

Answer

I think this is Roller Coaster World by Kenneth Bulmer (1972), in which, as you say, the setting is a world of mobile cities, moving in search of stimulative radiation ("Parsloe's Radiation".) To quote the cover blurb:

Parsloe's Planet was in its death throes. A world of mobile cities, the populace had moved frantically from radiation site to radiation site - for without this life-giving radiation the inevitable result would be insanity and death.

Now the radiation was failing. Soon it would be no more. The planet was going to die.

The radiation is also called "berries":

Of course Wormleigh had not been able to feel the increase in Parsloe's Radiation. The effects were too subtle. ... Everyone claimed a private gimmick to tell when Papa's Rad was beating strongly into them. If they did poorly at anything they'd say: "The berries must have been weak." ...