THe biggest block in my neck of the woods is the A34 south of Chilton. There is no cycle provision, it's one of the heaviest used dual carriageways, and there is a 1-mile section where there is no alternative N-S cycle route for 8 miles in either direction. There's never a safe time to use it as it is the main truck route from the Midlands to Southampton docks and it's also heading to the base of a steep hill where drivers are concentrating on not getting stuck behind something.