Graeme Wall wrote:
On 19/06/2019 18:02, Basil Jet wrote:
On 19/06/2019 14:03, Graeme Wall wrote:
On 19/06/2019 13:34, Recliner wrote:
On Wed, 19 Jun 2019 12:24:15 +0100, Roland Perry
wrote:

In message , at 12:04:50 on
Wed, 19 Jun 2019, Recliner remarked:

I pointed out that the buried/bridged
motorway will be built on a new alignment, to the west of the current
M25, so building it won't disrupt the existing motorway or flights.
Only the short period of linking the old carriageways and new
diversion will cause any disruption, and that should be short (mainly
a few days or weeks of lane closures, then a few hours of complete
closure while the traffic is switched to the new route).

It's far too close to the intersection with the M4 for the geometry to
work. Not only that, Heathrow's own information shows the M25 route
undiverted (only local roads have new corridors):

https://aec.heathrowconsultation.com...tes/5/2019/06/

P1-11-Local-Roads-Diverted.jpg

Thanks for that. That map clearly confirms the M25 diversion to the
west: it has a more pronounced curve under the runways than the
current route. It's a small enough diversion not to need any changes
to the M4 junction.

I've overlaid a translucent Google Map view on top of the new map, and
you can clearly see the diversion.

https://www.flickr.com/photos/recliner/48091808766/in/dateposted-friend/lightbox/



That confirms it is going to be foul of the current interchange which
is going to be less easy to adapt.

... although no bridges in either junction will have to be rebuilt.


If the new layout is foul of the current junction how is that going to work?


You first connect the completed new carriageway and its M4 slip road to the
old slip road just before it splits into the east and west bound links. For
the next few months, traffic heading for the M4 will be diverted to the new
northbound carriageway, while through traffic will continue to use the
existing carriageway. During this time, the new carriageway will be built
through the old northbound slip road to connect to the ood carriageway.
Again, there will be and closures for a few weeks and an overnight complete
closure as the final connection is made.

Southbound is easier, but, again, connecting traffic from the M4 might
continue to use the old carriageway for a little while after the through
M25 traffic has been diverted to the new carriageway.