The message
from Mike Barnes contains these words:

As far as
motorways are concerned I am not at all sure that 85 mph is actually
high enough to bring 85% within the law. 90 mph might.

Obviously time and place matter. I don't do a lot of motorway driving
but I happened to do Manchester-Stirling and back recently. I trundled
along at my usual 77 mph (83 on the speedo), and I estimate that far
less than 5% of the traffic overtook me.

The thing that I find difficult to judge is how much traffic is not
going much the same speed as me. I do find that if I happen to be doing
90 as I occasionally do (per gps) very little passes, 80 and there is
likely to be a constant stream (sometimes headed up by a police car)
passing at more than walking pace hence my thought that 85 might not be
high enough.

--
Roger Chapman
Nearest Marilyn still to be visited - Great Orme.
89 miles as the crow flies,
considerably more as the walker drives.