The success of the new average speed cameras on the A9 still does not address the problem of frustration caused on the single carriageway sections with different speed limits for normal vehicles and PSVs or HGVs.
Regularly a build-up of 60mph-limit vehicles behind a 50mph-limit bus or truck occurs, with the same slower vehicle refusing to pull in at the numerous lay-bys to allow the line behind him to overtake.
I regularly drive a bus along the A9 and find it costs a few seconds to pull in and out again in one movement, often without needing to stop, to allow this procedure. Yet how often do police stop drivers to advise (and occasionally penalise) those who will not do so?
This applies to all non-urban roads, of course, from the A9 to single-track with passing places.