WHBM wrote:A timely thread. I had voted for M25 J28 (A12) on the "Next stacked roundabout to be upgraded" thread, and then yesterday morning (3 May) a site meeting in Essex was grossly disrupted because a classic Gridlock had occurred, again, on the signalled roundabout at this junction. Looking at Google Maps traffic (because I had escaped it and was waiting for the others) traffic was backed up for several miles on all approaches, the M25 eastbound back to the M11, M25 westbound back to Lakeside, the A12 halfway back to Chelmsford, etc. Both colleagues and the client were stuck in it, and I ended up being co-ordinator of the issue.
One colleague who was late anyway (as ever ....
) on M25 eastbound I was able to divert, by phone, via M11 northbound, thence A414 etc.
The jammed traffic typically makes a complete circle in all lanes round the roundabout, and then backs up all the ramps and disrupts/jams the mainlines so through traffic cannot reach the freeflow overpass etc. It's well known across Essex for this happening regularly.
WOW just WOW and HE dont want to fix it?
First I would put in left filter lanes on three of the corners of the roundabout at least.
Obviously the corner with the services and the A1023 cant have it unfortunately but there could be left filters into the services and the A1023 at least. All of that could be done without structural alterations to the roundabout, eg just painting new markings!
Second a roundabout at the entrance to the services on the A1023, that would mean people could turn around at the roundabout if they are coming from the A12 westbound to M25 southbound.
At that point only right hand movements would need to be on the main roundabout.
Then when there was more money available a freeflow left turn from the A12 westbound to the M25 southbound bridge over the A1023.
After that right turn freeflow bridges going M25S-A12W, A12W-M25N, M25N-A12E and A12E-M25S, which would leave the services and A1023 accessible from the main roundabout only, so very limited traffic left.
Even if the right hand movements were on the roundabout still though, thats half of the movements gone and should allow better flow.
A 5 level stacked junction would be quite cool though! I can imagine that with the right hand movements 2 dual carriageway bridges could be built across the junction, one carrying the A12W-M25N and the A12E-M25S movements, the other carrying the M25S-A12W and the M25N-A12E movements.
Of course they could always close the A1023 entrance to the main roundabout and make that join the A12 directly going east for local traffic. Then get the service operator to pay for the bridge links to make their services link to more than just the westbound A12 and the southbound M25, if they want to link directly to the other carriageways. That would mean the main roundabout would only need to deal with the M25 and A12 right hand movements as the left hand ones would all be able to be left filter lanes.
