The authorities intend having about 60 miles of the A9 north of Perth covered by average speed cameras next year.They say the A77 ones have reduced casualties and this would happenon the A9, a dangerous road.Some lorry drivers oppose them because they would enforce the law making artics drive at 40mph. They say this would cause massive queues, but other road users believe they would allow safer overtaking instead of having cowboy truckers beasting on at 60mph.