Bletchleyite
Veteran Member
If you're doing this, you'd need to clear up the distinction between Dual-Carriageway roads with cross-traffic and frequent roundabouts and HQDCs that are not motorways for political/practical reasons (e.g. A14, A55). There's no good reason (in general) a 2-lane road with continuous Central reservation shouldn't be the same speed as a Motorway.
True. I suppose you could (and this might solve part of the smart motorway issue) define a motorway for these purposes as:
1. Has a continuous central reservation with a crash barrier and no right turns
2. Has a continuous hard shoulder of a specified minimum width
3. All public junctions including any lay-bys have acceleration/deceleration lanes of a minimum specified length
4. Does not permit cycling, pedestrians or other low speed vehicles
The ones you mention (I'd add A34, A5D* through MK, the Tingewick bypass on the A421) do fulfil (1) and look like motorways, but do have some non-motorway hazards like short laybys and no hard shoulder, which like the absence of (1) do increase the overall risk. Most of them also permit cycling which is a further potential hazard not present on a motorway.
The easiest way to classify these would be to very slightly loosen what can be described as An (M), while at the same time mandating smart motorways where there is no hard shoulder to be permanently set to 60 on the displays, and any sections of classic motorway without a hard shoulder or with particularly short acceleration lanes on a junction (there are a few; Leicester Forest used to be really short but has now been fixed) to be signed down to 60 through that section.
* Diversionary; not a formal name but is used locally to differentiate from the "old A5" i.e. V4 Watling St.
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