Returning from Wales on Friday, I chose to vary my route (I wish I hadn't, but that's another point), going down the A470 from south of Rhayader and then the A40 to Gloucester; yes I could have taken the A479, but wanted to see the network around Brecon. Picking up the D2 at Abergavenny, I noticed two striking things:

1. Having had a painful drive through Abergavenny, where the A40 goes right through the centre of town (I don't know if it was market day, but we were at a crawl), you then pick up a D2 that is almost motorway standard, apart from the Raglan Roundabout, until it meets the A449 at a junction that seems absolutely brilliantly engineered.

2. The A40, having picked up from the A449, is still almost at motorway standard until it meets the A466 at Monmouth at lights. From then on till Ross-on-Wye, the road is of a much less high quality, with no metre strip for most of the way (perhaps some Sabristi would correct me on that), sections where a new carriageway has been placed alongside the old, and houses fronting straight onto the road.

Couple of questions for those in the know:

1. Why does the HQDC end so abruptly at Abergavenny? Was the A465 Heads of the Valleys Road supposed to link up with the A40? If so, why is no bypass for Abergavenny planned? The A40 is a real bottleneck there. Unless (in WAG terms), the A40 west of Abergavenny is not a trunk road.

2. Is there anywhere else where a really high quality dual carriageway gives way to something far inferior, while still continuing at D2? I know we have Handcross to Warninglid on the A23 here in Sussex, but that was always intended to be improved.

The only example I can think of that sort of fits your criteria would probably be the somewhat unfairly chosen "double roundabout mayhem" with the M3 and N3. M3 is fully grade separated, 2 lanes plus hard shoulder in each direction. Once on the all purpose N3 the two lanes are retained, hard shoulder plus all the motorway equipment disappears and is NOT grade separated as there is a whacking great roundabout with the R163 halfway-ish along.

My reasoning to the unfair disclaimer at the top of this post is that I'm comparing a motorway to an all purpose road. It does highlight the differences between motorways and certain dual carriageways, even if they both look the exact same in the legislation.

It does get poorer in quality when you reach Aber, but goes a bit further (to Gilwern) as a decent enough DCIt does, at AberBecause it has already been built! (at least on the A465 N-W axis, linking with the A40 to the east and A4042 to the south)It is.

A recent discussion of routes into West Wales did wonder why the A40/trunk route still goes through the middle of Aber, instead of via the current A4143, which misses the centre though still goes in the residential area for a bit.

I've come up with this sort of solution for completely avoiding the Aber urban area (in blue). Also a way of bypassing Crickhowell for not a huge cost. 3 bridges over the Usk (one for Aber, two for Crickhowell), and in the National Park - highly unlikely to happen, even though there's not much new road:

A1 Redhouse to Darrington sounds like a good contender!

I should imagine there are lots of roads around the country like this where upgrading to D2 has taken decades to complete and the quality of the road indicates its vintage. Probably too many to list. Here's one or two i know of:

A303, particularly Ilchester to Ilminster. Fairly high quality 1990's gives way to older 1970s D2 at South Petherton.

A27 between M27 and Worthing, regularly switches between modern HQDC and much older, lower standard sections, including Chichester bypass and between Westhampnet and Fontwell.

A38 Devon Expressway, like the A27 routinely switches between HQDC and older D2 sections. M5 to Chudleigh in particular spring to mind. Going southbound its Sub-Motorway up to Haldon Hill then old bendy D2 after the racecourse.

If we are talking Motorway to APDC (not sure if it counts though) then the classic one for me would be M27-A31 at J1. Same road but what a contrast in quality!

I always use the A4143 that skirts around Abergavenny to the west instead of using the A40 through Abergavenny and I've never had a hold up along there.

The A40 from Monmouth to Ross-on-Wye was built mainly along the route of the original A40 and dates back to the early 1960's and hasn't changed much since then. The A40, then A449 from Raglan to the Coldra where it meets the M4, was a new road, so there were no buildings to pass or compromises in design. This section has been improved over the years and it has a little more space to add a metre strip.

I think it would be very difficult to make any major improvements to the section from Monmouth to Ross-on-Wye where the road is in the Wye valley and running through Symonds Yat and I'm sure there would be huge local opposition to any major scheme. I quite like this section as it is rarely very busy but it's a bit quirky and more interesting than a flat, straight road, like the A40 from Abergavenny to Raglan.

In my neck of the woods, I can think of the A19. Near motorway standard through Teesside with stretches as wide as D4 and a fully free flowing junction between the A19 and A66 that even puts motorway/motorway junctions to shame for free flow and capacity. But north of Teesside and the Billingham Bypass, the road becomes littered with at-grade gap intersections with rural roads which is dangerous on a stretch of road that is very busy at peak periods. The A19 south of Teesside also has at-grade gap intersections between Crathorne and Thirsk but traffic isn't as dense to make this a serious concern. That said, the Black Swan Crossroads was grade separated because it developed a poor accident record but I think the issue related to the amount of local traffic that needed to cross over the A19 at this junction.

Arguably, and this often also seems the case elsewhere, the 1970s sections are of higher quality than he 1990s bits. Certainly in terms of slip road lengths and quality.

The top end of the A1(M) at Peterborough is quite striking, you go from 4 lane motorway, to three lane motorway, to old 2 lane all purpose road, with a twisty 1960s alignment.

All good examples; I am so used to the bad bits of the A27 I don't really notice the good bits, as they're not long enough to form a single, decent quality road: The only good bits are the Brighton and Hove bypass (and the section from Patcham to Stanmer Park is arguably less good quality), the Patching-Clapham diversion, which was intended to link up with the Worthing bypass which was abandoned, the Crossbush bypass, which was supposed to link with the Arundel bypass (again abandoned), and Chichester to Havant plus the existing Havant to M27 section, which are really the only bits that are near motorway standard. The Westhampnett bypass I cannot understand: A full GSJ at the not particularly busy A285 junction, then the road meets the old A27 (far busier) at yet another bally roundabout on the Chichester bypass. With the A40, it just seemed that the change from HQDC to a substandard road was particularly noticeable: Does anyone know whether the high quality section was intended to go beyond Monmouth?. Redhouse to Darrington (which I am very familiar with from coach trips following the Albion) I forgot about partly as it's surrounded by motorway on either side, but yes, I suppose the contrast there is pretty huge.

I was thinking the other way around. Later dualling has hardstrips and (some) GSJs while the 70s section has a crossroads and no hardstrips and generally feels more claustrophobic. Despite having a strange mix of GSJs and at grade junctions the 1990s section is the better section of the two IMO.

The A31 Hogs back.

Not to mention the other end at Alconbury.

I would nominate the A2/M2 route from M25 to Dover. It starts as D4H as you keave the M25 and gets narrower and narrower as you get closer to the coast. D4 AP - D4 Motorway - D3 Motorway - D2 Motorway - D2 AP - S2 AP.

Tony

The single track bit of the A887 in the middle of two modern S2 sections springs to mind.

The A82 out of Glasgow is a variety of roads, firstly the old Victorian/Edwardian Great Western Road, then the 1920s Boulevard with up to 3 lanes each way, but basically only 2 lanes in the same carriageway width, then the narrower section through Dumbarton before the 1970s Alexandria Bypass. For a starker contrast, keep going up the 1970/80s S2 to the road north of Tarbert which is barely changed since Telford built it in the 1810s.

The A86 also changes rather abruptly, from the WS2 built with EU money in the 1990s to Telford's near-200 year old road just here.

The A5 varies from wide dual-carriageway in various places in the Midlands, to Telford's narrow and twisty coaching road through north Wales.

The A41 out of London springs to mind; from the end of the A1 multiplex there's an interesting mix of plain S2 (in North Watford), WS2 with reserved strips for dualling (and an extra-wide bridge over M1), at-grade D2 and even a couple of lavish GSJs (with M1 and the North Orbital)thrown in. After the M25 jct. there's the long Langley - Berkhamsted Bypass section; classic bargain basement 90s HQDC with some ridiculous slips and interesting gradients, but a good quality mainline nonetheless. Next is the ex-A41M Tring Bypass, with shoulders and a rough surface which contrasts with that of the next section, the Aston Clinton Bypass from 2003. This is essentially one massive sweeping bend, speaking of the greater lengths gone to to avoid properties nowadays than in the 70s when the preceding section cut straight through Tring Park. At the end of this section it gives up and plods meekly into Aylesbury.

I drove the A39 from Wadebridge to Street on Sunday. No D2, but I was amazed by the S1-with-passing-places bit by Lynmouth. Incredible that this is an F99 road in England.

I believe there was another scheme to upgrade the A1 southwards past Brampton Hut and Buckden, but the NIMBYs prevented it from happening. That is why the current splended Alconbury to Peterborough section is somewhat isolated!

Chris.