[esquire]

^ Your numbers 2 and 3 are no-brainers, definitely in need of twinning. 1 and 4 are really not that busy by traffic count to justify twinning... although the 6 is a somewhat treacherous highway for other reasons (many long haul drivers, etc.) where those factors could bump it up the priority list somewhat.

An Oakbank expressway (which has been planned for years if not decades now) could obviate the need to twin the 15 to Dugald.