jacobean wrote:Having to continually check routes with a smartphone or may takes the complete enjoyment out of cycle touring.
Sometimes you're better off on a secondary road(safety permitting of course).
Correct. In fact once close enough to a town or city centre that traffic is down to 30mph the major A roads can often be OK. Even time lost at traffic lights is cancelled out by saving time lost in frequent map checks.
For example the A74 is fine for cycling from Tannochside SE of Glasgow up to the city centre where it meets the A8.
Going west the A8 is fine as far as Bishopton past Paisley. It becomes a 70mph dual carriageway between Langbank and Port Glasgow. I see cyclists on it but I would avoid. Much of the old A8 and all the old A74 is now just local traffic as the M8/M74 carries all the through traffic.