In article , Roland Perry
writes
I have never in my life seen construction companies do this
even when the new road is well away from the old route
It costs millions extra to do it that way

Come and look at the A14 rebuild between Girton and Swavesey. It's being
done in a similar way.

And there's only disruption to the through traffic for two isolated
overnight periods (while they switch some virtual points)?

You have got-to-be-joking.

Let's see when it happens.

At the moment, the next disruption is a closure this weekend to demolish
what's left of the old Bar Hill flyover. Closures for this sort of
thing, or installing gantries, seem to be more disruptive than switching
the alignment.

--
Clive D.W. Feather

tim... wrote:


"Recliner" wrote in message
...
tim... wrote:


"Recliner" wrote in message
...
On Wed, 19 Jun 2019 12:43:48 +0100, "Clive D.W. Feather"
wrote:

In article , Roland Perry
writes
The only disruption will come at the end, when the traffic is
diverted
to
the new route. My guess is that the northbound traffic will be moved
first,
with a few weeks of lane 1 closures required while they connect the
new
to
the old carriageways, then an overnight closure for the final switch
to
be
made. The same procedure would then be followed a few months later to
divert the southbound carriageway to the new alignment.

The amount of work you would be expecting them to do "overnight"
beggars
belief.

I disagree.

Build the two new carriageways. At each end, cut them off very close to
the edge of northbound lane 1 (there's no hard shoulder, right? if
there
is, adjust description accordingly).

Cone off northbound lane 1. Spend a week or two filling in the narrow
gap between the old and new northbounds at each end.

Not sure that you even need a closure to switch over. Simply move all
the cones.

Repeat for the southbound (though this time you're closing lane 4).


Yes, that's what I'm expecting.

I have never in my life seen construction companies do this

even when the new road is well away from the old route

It costs millions extra to do it that way

Why would it cost any extra?

because you have to build a "throw away" access road to the new build road.

I take it you've never looked at a map of the area, or even Google Maps?


The alternative of accessing via the current road is "free" but causes some
of that road to need closing

There are plenty of other existing roads, including the A4, they can use
for access to the work sites.

tim... wrote:


"Recliner" wrote in message
...
tim... wrote:


"Recliner" wrote in message
...
On Wed, 19 Jun 2019 10:57:29 +0100, "tim..."
wrote:



"Recliner" wrote in message
...
tim... wrote:


"Recliner" wrote in message
...
tim... wrote:


"Recliner" wrote in message
...
https://www.bbc.co.uk/news/business-48668001


well I don't know about the rest,

but I for one think that the idea that people who have little or no
business
at the airport are going to have to suffer 5 years of disruption
whilst
they
rebuild the M25 to create this Hub airport entirely unreasonable

Why do you think M25 users will suffer five years of disruption?
It's
more
likely to be a few night time closures or lane restrictions.

they are going to put the whole road in a tunnel (presumably from the
way
it's described not by building a raft on top of it)

how can that not cause major disruption?


You've obviously not looked at the map,

what is "The Map" - I guess there is one, but no I didn't get to see it
(You
can blame that on my out of date browser if the original article
included
a
link)

or read this thread.

as one of the first to reply, that would have been difficult

If you now read the thread, 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.

The plans that I can see show the new road so close that the idea that it
wont disrupt the current M25 is fiction.

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).

If you think that they can link a new route into a current motorways by
only
diverting traffic for a few weeks then you have never seen how they do
this

IME they narrow the road where the connection is to be made for the full
term of the works. They do this because they need access to the new road
for construction vehicles - how else are they going to build it?

They won't need access to the existing M25 to build the new structures to
the west — why would they?

because they don't helicopter all the construction stuff in, do they


Of course not.

Why don't you at least look at a map before posting an inane question like
that?

On 19/06/2019 22:06, Recliner wrote:
tim... wrote:


"Recliner" wrote in message
...

They won't need access to the existing M25 to build the new structures to
the west — why would they?

because they don't helicopter all the construction stuff in, do they

Of course not.

Why don't you at least look at a map before posting an inane question like
that?

Of course! They can fly everything in on the new runway.

--
Basil Jet recently enjoyed listening to
Prefab Sprout - 1985 - Steve McQueen

On 19/06/2019 21:07, Recliner wrote:

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.


I don't know what the limit is on how close junctions are allowed to be
on motorways, but that might put the T5 junction and the M4 junction too
close together during the interim, leading to dangerous weaving.

--
Basil Jet recently enjoyed listening to
Feist - 2011 - Metals

Basil Jet wrote:
On 19/06/2019 21:07, Recliner wrote:

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.


I don't know what the limit is on how close junctions are allowed to be
on motorways, but that might put the T5 junction and the M4 junction too
close together during the interim, leading to dangerous weaving.


Why would they be any closer than they are now? In any case, there are
much closer motorway junctions elsewhere.

On 20/06/2019 00:09, Recliner wrote:
Basil Jet wrote:
On 19/06/2019 21:07, Recliner wrote:

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.


I don't know what the limit is on how close junctions are allowed to be
on motorways, but that might put the T5 junction and the M4 junction too
close together during the interim, leading to dangerous weaving.

Why would they be any closer than they are now?

Because at the moment the traffic for the M4 leaves the main carriageway
a fair distance north of the A4, whereas you would have this traffic
using the new tunnel route (and the through M25 traffic using the old
route) for a few months, which puts the bifurcation point inches north
of the convergence point at the north end of the T5 junction. That's not
going to work. Similar for the southbound. The traffic to and from the
M4 and the traffic to and from Watford has to remain together throughout
the construction to avoid dangerous weaving at the north end of the T5
junction (although obviously the northbound can switch to the new tunnel
months before the southbound does).

--
Basil Jet recently enjoyed listening to
Feist - 2011 - Metals

Basil Jet wrote:
On 20/06/2019 00:09, Recliner wrote:
Basil Jet wrote:
On 19/06/2019 21:07, Recliner wrote:

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.


I don't know what the limit is on how close junctions are allowed to be
on motorways, but that might put the T5 junction and the M4 junction too
close together during the interim, leading to dangerous weaving.

Why would they be any closer than they are now?

Because at the moment the traffic for the M4 leaves the main carriageway
a fair distance north of the A4, whereas you would have this traffic
using the new tunnel route (and the through M25 traffic using the old
route) for a few months, which puts the bifurcation point inches north
of the convergence point at the north end of the T5 junction. That's not
going to work. Similar for the southbound. The traffic to and from the
M4 and the traffic to and from Watford has to remain together throughout
the construction to avoid dangerous weaving at the north end of the T5
junction (although obviously the northbound can switch to the new tunnel
months before the southbound does).


I don't think it would be possible for the northbound through and M4
junction traffic to stay together throughout, as the new through route cuts
through the existing slip road to the M4. So there would have to be at
least a short period of a few weeks of separation while the through route
is linked at the northern end, through the current M4 junction slip road.
Maybe there would have to be restrictions on the use of the junctions
during that transition period? For example, T5 to M4 traffic might be
rerouted.

Southbound might be easier, and it might be possible to keep the traffic
flows together. Or, again, M4 to T5 traffic could be temporarily rerouted
for a few weeks.

On 20/06/2019 01:04, Recliner wrote:
Basil Jet wrote:
On 20/06/2019 00:09, Recliner wrote:
Basil Jet wrote:
On 19/06/2019 21:07, Recliner wrote:

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.


I don't know what the limit is on how close junctions are allowed to be
on motorways, but that might put the T5 junction and the M4 junction too
close together during the interim, leading to dangerous weaving.

Why would they be any closer than they are now?

Because at the moment the traffic for the M4 leaves the main carriageway
a fair distance north of the A4, whereas you would have this traffic
using the new tunnel route (and the through M25 traffic using the old
route) for a few months, which puts the bifurcation point inches north
of the convergence point at the north end of the T5 junction. That's not
going to work. Similar for the southbound. The traffic to and from the
M4 and the traffic to and from Watford has to remain together throughout
the construction to avoid dangerous weaving at the north end of the T5
junction (although obviously the northbound can switch to the new tunnel
months before the southbound does).


I don't think it would be possible for the northbound through and M4
junction traffic to stay together throughout, as the new through route cuts
through the existing slip road to the M4. So there would have to be at
least a short period of a few weeks of separation while the through route
is linked at the northern end, through the current M4 junction slip road.
Maybe there would have to be restrictions on the use of the junctions
during that transition period? For example, T5 to M4 traffic might be
rerouted.

Southbound might be easier, and it might be possible to keep the traffic
flows together. Or, again, M4 to T5 traffic could be temporarily rerouted
for a few weeks.


The M4 to T5 or T5 to M4 isn't the problem, because it keeps left
through the pinch point. The problem northbound is the Gatwick to
Slough traffic cutting from right to left exactly where the T5 to
Watford traffic is cutting from left to right, and southbound the Slough
to Gatwick traffic cutting from left to right exactly where the Watford
to T5 traffic is cutting from right to left.

So there is no way the bifurcation point or merge point south of the M4
junction will be moved to the north end of the T5 junction even for a
one minute period, unless the motorway was down to one lane there, which
is only feasible in the middle of the night.

--
Basil Jet recently enjoyed listening to
Feist - 2017 - Pleasure

Basil Jet wrote:
On 20/06/2019 01:04, Recliner wrote:
Basil Jet wrote:
On 20/06/2019 00:09, Recliner wrote:
Basil Jet wrote:
On 19/06/2019 21:07, Recliner wrote:

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.


I don't know what the limit is on how close junctions are allowed to be
on motorways, but that might put the T5 junction and the M4 junction too
close together during the interim, leading to dangerous weaving.

Why would they be any closer than they are now?

Because at the moment the traffic for the M4 leaves the main carriageway
a fair distance north of the A4, whereas you would have this traffic
using the new tunnel route (and the through M25 traffic using the old
route) for a few months, which puts the bifurcation point inches north
of the convergence point at the north end of the T5 junction. That's not
going to work. Similar for the southbound. The traffic to and from the
M4 and the traffic to and from Watford has to remain together throughout
the construction to avoid dangerous weaving at the north end of the T5
junction (although obviously the northbound can switch to the new tunnel
months before the southbound does).


I don't think it would be possible for the northbound through and M4
junction traffic to stay together throughout, as the new through route cuts
through the existing slip road to the M4. So there would have to be at
least a short period of a few weeks of separation while the through route
is linked at the northern end, through the current M4 junction slip road.
Maybe there would have to be restrictions on the use of the junctions
during that transition period? For example, T5 to M4 traffic might be
rerouted.

Southbound might be easier, and it might be possible to keep the traffic
flows together. Or, again, M4 to T5 traffic could be temporarily rerouted
for a few weeks.


The M4 to T5 or T5 to M4 isn't the problem, because it keeps left
through the pinch point. The problem northbound is the Gatwick to
Slough traffic cutting from right to left exactly where the T5 to
Watford traffic is cutting from left to right, and southbound the Slough
to Gatwick traffic cutting from left to right exactly where the Watford
to T5 traffic is cutting from right to left.

So there is no way the bifurcation point or merge point south of the M4
junction will be moved to the north end of the T5 junction even for a
one minute period, unless the motorway was down to one lane there, which
is only feasible in the middle of the night.


Perhaps the simplest approach would be to close the T5/M25 northbound
connection for a short period while they work round the clock to connect
the new through carriageway at the northern end, cutting through the
existing slipway. T5 traffic could be diverted via the A3113 or Colnbrook
Bypass.