M3 - A31 Comments

The onslip here has now become a 'ghost island' merge, with two lanes and adequate room for HGVs to speed up, so I think this should now be upgraded to 'Mundane Junctions'.

To be honest, the best solution would be to make junction 8 a proper junction so that you can join and leave the A303 from both directions. This would then also reduce the congestion on that part of the A34.

The hills and existing roads here made it difficult to come up with a decent set of junctions, and I imagine that the budget was quite small after building the Twyford cutting. The real problem however is the A34. I am unaware of any plans, but I would hope that this junction will be improved soon, as has been done at the A34/M4 junction.

The gradients when joining the M3 at Twyford could be eased by building crawler lanes (I think there may just be room to do this without needing to cut more rock) as planned for Portsdown Hill on the M27. I think that this would help ease congestion all the way back to the southern end of the M3 in the mornings, and back to J9 in the evening. Not the best solution, but substantialy cheaper.

The main problem with this junction (along with the junction on the other side of the cutting) is the steep gradients on the sliproads. Coming off the motorway you really have to brake firmly to slow down, and joining the motorway you have to really rev the car before changing gear in order to join the motorway at a reasonable speed. Of course, there tends to be traffic in front, and these drivers aren't fussed about joining the motorway at 35mph!

The suggestion you make about placing the A31/M3 southbound slip to the south of the site is unfortunately impossible, as the road is climbing amazingly steeply at this point, which would make the on-slip even steeper than it is at the moment, which in itself is ludicrous.

To be honest, the junction you highlight simply should not be there at all. The A31 comes to a stop one roundabout earlier, where the spitfire link goes up to the A34/M3 junction. This is fine for (what little) northbound traffic there is. The idiocy of the whole arrangement of the M3 between J11 and J9 is that the old road, to the west of St Catherines Hill (the alignment of which is still obvious on an aerial photo), should never have been removed. This should have been kept for A31 southbound traffic to then join the M3 south at J11. This would also have allowed traffic for Winchester south to exit at J11 and follow the old A31. J10 is not only a pointless waste of time, but the weaving that it causes on the northbound carriagway has to be seen to be believed. The problem is that traffic joining at J11 northbound does so at a snails pace (the uphill slip is again ridiculously steep) and so traffic on the M3 moves over one or maybe two lanes. At that point faster traffic from J11 pulls out, just as traffic for J10 is trying to move over 2 lanes... the entire 3 lanes of motorway becomes one big weave!

From a local perspective, it's not quite as bad as you make out... The A31 really comes to a halt at the next roundabout to the north, where any northbound traffic (for the M3 north, the A33, the A34 and local northern Winchester traffic) heads up to J9, whilst anything going south comes to this junction.

The weird routing from city to M3 is indeed strange, but overall, the junction (I am sure, as you suggest, done on the cheap) does seem to work OK. Maybe the junction was designed with more local knowledge than many?

Although you have correctly identified the M3-A31 junction at Winchester as a 'bad junction', you have neglected to highlight:

* The horrifically steep and curved southbound entry slip onto a blind bend of the motorway - anyone stuck behind a lorry at this point has to merge with the traffic coming through the Twyford cutting at around 20mph.
* The recent and wholly unnecessary addition of traffic lights on the western roundabout.
* The bizarre signposting around Winchester which takes all city-bound traffic leaving the M3 or A34 at junction 9 all the way down to junction 10 (alongside the motorway), around both roundabouts and back north again.