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Old June 19th 19, 04:14 PM posted to uk.transport.london
Recliner[_3_] Recliner[_3_] is offline
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Default Latest Heathrow master plan

Graeme Wall wrote:
On 19/06/2019 14:29, Recliner wrote:
On Wed, 19 Jun 2019 14:03:37 +0100, 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.


Yes, it looks like there will have to be a small adjustment to the
northbound slip roads, but that should be relatively easy, as it will
make them straighter.


Except you have to take the change in levels into account which will
involve major construction works and you can't build the new sliproad
alongside and move the traffic over.


There won't be any change of levels where the new and old carriageways meet
— that'll be further south. But I agree that the connection stage will be
more complicated as it'll involve the slip roads as well as the main
carriageways.

I think what they might do would be to first move the northbound M25
traffic for the M4 on to the diversion so that it can then use the new slip
roads. The new through carriageway can then be extended over the old slip
roads to connect to the old through carriageway.