M25 junction 28 improvements

[crowntown100]

When I first looked at that, I wondered whether they were planning on later adding in the Dark Blue slip road on my poor drawing of the my imaginary full layout of the scheme. However, that it completely redundant as there is an unhooked left turn at J28, so why would they then do that... Still not sure.

(The drawing is by no-means perfect. It is just a ten minute mock up of what I'd do, ignoring the fact that the A12 from London now plugs directly into the roundabout.)

[jackal]

Statutory consultation. No real change, still a basically sound design, but I'm still not keen on the sharp turn at the start of the loop.

https://highwaysengland.citizenspace.co ... sultation/

[Bryn666]

That loop is going to be a safety problem down the line. A smoother alignment was surely possible.

You're looking at a potential 30 mph curve on top of a structure which if a vehicle breached the parapets they'd be on the carriageway below.

Surely RSA1 picked that up.

[jackal]

The original consultation had two smoother options for the curve as well as the tight one. Seemingly all are the same 75kph design speed, which I agree is hard to believe for the preferred route.

One of the options (5C) is basically a smoother version of the preferred route (5F) but with only one lane. I think 5F's tight curve is the designers' way of making space for a generous two-lane diverge without increasing land take. Common sense would suggest the loop's horizontal geometry should take priority over providing a tigertail or whatever.

https://highwaysengland.citizenspace.co ... ochure.pdf

[jackal]

Supplementary consultation on minor changes to the scheme:

https://highwaysengland.citizenspace.co ... sultation/

[Peter Freeman]

No real change, still a basically sound design, but I'm still not keen on the sharp turn at the start of the loop.

Yes, "basically a sound design", and I don't share the worries about geometry/radii on the 270 loop. However, the brochure says that a problem is the Nags Head traffic signals causing queues to backup onto the roundabout. The proposal doesn't address that issue. Perhaps some work should occur at that intersection too (I haven't actually looked at it).

Also, if the northbound to eastbound turn is heavy then presumably westbound to southbound is also heavy, and therefore, if the Brook Street arm (the only unsignalised one) carries significant traffic, then it should also be signalised. Although I dislike roundabout signalisation, once you do it you should do it properly, usually meaning completely.

It's a pity a filter lane ('jet-lane') for a direct left turn westbound-to-southbound isn't feasible, owing to Brook Street being in the way. A bridge could fix that problem of course, and there is space.

[jackal]

You can see AM peak volumes here:

The next major upgrade would probably be to freeflow westbound to northbound, as shown in this ambitious HE plan:

[c2R]

If they do that they might need to consider actually widening the Brentwood bypass. I can imagine it will become a bit of a bottleneck northbound in the evening peak...

[Peter Freeman]

You can see AM peak volumes here:

Thanks for those figures. The volume symmetries exist as expected, and so a free left turn at the SE corner does seem necessary, and it would be the easiest next addition (one structure).

The next major upgrade would probably be to freeflow westbound to northbound, as shown in this ambitious HE plan:

That is ambitious, but yes, it complements the existing NE corner jet lane, which is in the correct position. A cheaper version of that turn would be another 270 loop, but it looks a bit tight. Use a lower design speed, with warning signs?

The take-away from this difficult problem is, once again: don't build any more of these discredited stackabouts. They are expensive, land-hungry, perform poorly - and are difficult to rectify without wastage, up to a disruptive complete re-build.

[c2R]

The take-away from this difficult problem is, once again: don't build any more of these discredited stackabouts. They are expensive, land-hungry, perform poorly - and are difficult to rectify without wastage, up to a disruptive complete re-build.

It's tricky, because their initial land-take isn't that high, compared with other junction types, and they aren't necessarily bad where turning traffic volumes are low, e.g. on the new junction east of Galway. And they aren't as expensive as a four level stack. However, the M25 was definitely under-specified, both in terms of capacity as well as in junction design.

[Chris5156]

The take-away from this difficult problem is, once again: don't build any more of these discredited stackabouts. They are expensive, land-hungry, perform poorly - and are difficult to rectify without wastage, up to a disruptive complete re-build.

It's tricky, because their initial land-take isn't that high, compared with other junction types, and they aren't necessarily bad where turning traffic volumes are low, e.g. on the new junction east of Galway. And they aren't as expensive as a four level stack. However, the M25 was definitely under-specified, both in terms of capacity as well as in junction design.

They also permit the inclusion of local roads - which is useful but adds further to their complexity, congestion and difficulty to upgrade.

Unfortunately it would be difficult to come up with a free-flow replacement for most stackabouts because they have more than four arms - M25 J28 being just one example.

[jackal]

Brook Street is fairly important (volumes are about half those of the western arm of the A12). It needs to plug in somewhere and putting it directly onto the A12 would create mainline weaving problems. So it's not hard to see how they ended up with a stackabout.

The ambitious plan is about right for the long run. The roundabout would be fine if it's only handling Brook Street and turns to/from the western arm of the A12, which has half the volumes of the eastern arm. A quirk of the plan is that there still isn't the freeflow left turn over/under Brook Street (this despite the fact the existing freeflow left is upgraded) but it could be added presumably.

[jackal]

This has been before the Planning Inspectorate since the summer. Works to start 2022 if approved. This is presumably considered a foregone conclusion as a £124m contract with GRAHAM has been signed.

https://www.eppingforestguardian.co.uk/ ... ring-2022/

[multiraider2]

Good grief, this needs doing now. I went to see my sister and her family on Saturday. It used to be an hour trip from my house with perhaps an extra 15 minutes needed if the tunnel and its approaches are slow. I saw the traffic on Google Maps showed red past J2 and so I left at 3.35pm for a target arrival time of 5.00pm. The tunnel was't actually as bad as had been suggested and I thought I might get there early. Oh no, wrong again Ian.

The queue from J28 anti-clockwise went back half a mile and Lane 1 looked fairly stationary. I pushed it a bit and cut into the lane as the slip road started at the dashed lines here. I was protected by cars still stationary behind me and others ahead who I knew were going to push in later. In three quarters of an hour from that point, I had not passed the gantry before the Greater Anglia rail bridge. At that point I gave up. When I passed the gore there were indeed many vehicles still in the running lane trying to get off and it looked utterly still on the roundabout below. I reckon my only movement was from other vehicles ahead giving up. I know Brook Street can get into a near gridlock position and I don't know if this was the case here or some other restriction onto or on the A12 itself. The cars who were in Lane 1 at the back may still be there now. The exit queue from the clockwise carriageway looked grim also.

I went to J27 and onto M11 J7 and the A414 and A128. There were a few cycles of the lights needed to exit at M11 J7 but the alternative route was uneventful until Pilgrims Hatch. Gas main works on the A128 there had me doing a u-turn and back along the Straight Mile to Ashwells Road and back roads back to Pilgrims Hatch. Roads I haven't driven on since the 1970s as a teenage cyclist. We arrived 6.25. Truly awful.

[Bryn666]

A cloverleaf would be more efficient than this horror show and that's saying something.

Removing Brook Street from the equation somehow is going to have to be a component of upgrades before long as well.

[Runwell]

Good grief, this needs doing now. I went to see my sister and her family on Saturday. It used to be an hour trip from my house with perhaps an extra 15 minutes needed if the tunnel and its approaches are slow. I saw the traffic on Google Maps showed red past J2 and so I left at 3.35pm for a target arrival time of 5.00pm. The tunnel was't actually as bad as had been suggested and I thought I might get there early. Oh no, wrong again Ian.

The queue from J28 anti-clockwise went back half a mile and Lane 1 looked fairly stationary. I pushed it a bit and cut into the lane as the slip road started at the dashed lines here. I was protected by cars still stationary behind me and others ahead who I knew were going to push in later. In three quarters of an hour from that point, I had not passed the gantry before the Greater Anglia rail bridge. At that point I gave up. When I passed the gore there were indeed many vehicles still in the running lane trying to get off and it looked utterly still on the roundabout below. I reckon my only movement was from other vehicles ahead giving up. I know Brook Street can get into a near gridlock position and I don't know if this was the case here or some other restriction onto or on the A12 itself. The cars who were in Lane 1 at the back may still be there now. The exit queue from the clockwise carriageway looked grim also.

I went to J27 and onto M11 J7 and the A414 and A128. There were a few cycles of the lights needed to exit at M11 J7 but the alternative route was uneventful until Pilgrims Hatch. Gas main works on the A128 there had me doing a u-turn and back along the Straight Mile to Ashwells Road and back roads back to Pilgrims Hatch. Roads I haven't driven on since the 1970s as a teenage cyclist. We arrived 6.25. Truly awful.

It seems, although not reported elsewhere, the issue was the sequencing of the traffic lights, which has apparently been a problem again today in to the evening and on a number number previous occasions. It seems some of the lights were only letting out two cars, other adjacent lights were green at the same time. Absolute chaos. Some drivers stuck for well over three hours at the junction, and a regular scenario. You would think HE, for such an overloaded junction, would have made sure this did not become a repeat problem, but it seems they only seem to find a quick fix. It will probably be the same problem again in a few weeks, maybe sooner than that?

[multiraider2]

It seems, although not reported elsewhere, the issue was the sequencing of the traffic lights, which has apparently been a problem again today in to the evening and on a number number previous occasions. It seems some of the lights were only letting out two cars, other adjacent lights were green at the same time. Absolute chaos. Some drivers stuck for well over three hours at the junction, and a regular scenario. You would think HE, for such an overloaded junction, would have made sure this did not become a repeat problem, but it seems they only seem to find a quick fix. It will probably be the same problem again in a few weeks, maybe sooner than that?

Thanks for the suggested explanation. The A13 was closed all weekend and it's also half-term. I wondered if both had also contributed. J29 was also heavy at the exit (that I suspect was A13 diverting traffic) and that perhaps convinced some others to go to the A12 rather than leave there for the A127/A130 route to Chelmsford and beyond. My sister and her husband say they mostly use J29/A127/B186 to get home and I might just do that from now on. That's certainly the way I came back today.

[Runwell]

As in B186 in to Brentwood (via Warley)?

The A13 closure might have played a part. The A127 has certainly been quite nasty on some weekends the A13 has been shut, in various stretches from before Basildon up to the M25 both ways. Most of the delays have been around the M25 junction, especially Southend-bound, where the J29 roundabout has seen traffic backing up and blocking the anticlockwise entry slip turn, and sometimes queuing back on to the M25. I think, in normal conditions though, when Brook Street is fine, staying on the A12, rather than head down the A13 on to the A130 and vice-versa is still the quicker route to the M25, even if going towards Docklands via the A13 after the M25 J30. If you're in the South of the County, it's still going to be quicker to tough it out on the A127 during these A13 closures, then go all the way up to the A12 (via the A130).

I don't think there was a half term rush around here. I headed up the A12 yesterday lunchtime to Colchester, and apart from a little bit of slow traffic up to Boreham (as per usual), it was running freely all the way past Chelmsford, whereas usually there'd be stop-start traffic up to at least Rivenhall during a school holiday Saturday afternoon.

Another problem yesterday was the really poor communication. Queues on the A12 weren't mentioned on BBC Essex until deep in to the afternoon (queues on the M25 weren't mentioned at all!), and then they were only reporting 20 minutes of delays, which show how badly inaccurate these things are. Also the matrix signs were apparently not displaying any warning of the problems at J28, although you may be able to verify that?

[multiraider2]

Yes, B186 up through Warley. It's not a huge secret locally but still quiet enough. You can also take a right at Eagle Way past the old Ford HQ (now being re-developed as apartments I note) and get to Brentwood via Hartswood or Shenfield/Hutton via the back.

Yes, there was nothing on the VMS at all. They were all showing 10 minute delays at M11 J9-J10. Google Maps suggested orange for the junction just before I left. I did have my sat-nav set to the fastest route, but it didn't suggest taking J29 until the queue had already started there in lane 1 and I thought "It's too late to join that now". I should have listened. I assume there is no actual number plate reading between 2 miles from the junction and the roundabout, but are there no traffic monitoring cameras at the junction itself? I'm assuming no one at National Highways or anywhere else actually knew there was such a serious issue or that they just couldn't resolve it for some hours.

Interesting that you heard reports of people waiting there 3 hours. That certainly looked possible based on the progress I wasn't making. This is, I assume, a similar fallacy as the sunk costs one in accounting. After waiting for some considerable time, people feel invested in taking the junction when the only consideration should be "From this point forward will it be quicker to my destination if I leave the queue?" Going to Chelmsford then certainly the A414 would have been. Going to Colchester then that or certainly the A120 would have been and even Brentwood with 26 miles instead of 2, that was the consideration that should have been made by all who had not past the gore, even before the first hour was up.

[BigBazz]

A burst water main on the sliproad from the anticlockwise M25 to the Westbound A12 hasn't helped matters.

Essex and Suffolk Water report that it was finally fixed yesterday lunchtime, after nearly a month of work.