Bez wrote:If you wouldn't, then what do you see as the significant difference between motorways and trunk dual carriageways that makes the latter suitable for cycling?
Motorways always started life as new constructions in addition to the existing road network (except where they severed back lanes, etc), and had no local traditions of being used by non-motor traffic. Many A-roads are not new supplements but are the neighbourhood's long-standing main roads and the only reasonably direct route from A to B, and in some case the only possible access to places located on them.
Similarly, motorways had practically no harmful impact on bus routes, but conversions of rural main roads with unrestricted side turnings into grade-segregated ones with motorway-style junctions has sometimes played havoc with rural bus routes where busses can no longer make the turns they used to for gaining access to villages and hamlets, or passengers cannot safely cross roads to access bus stops.