M4 junction numbers

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steve618
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M4 junction numbers

Post by steve618 »

I've started a new thread as the references are spread over a number of older threads and have several broken links.

Before it was extended westwards in 1971 the M4 terminated in a junction with the A4. J8 was the A308 and J9 was the end of the road. But where does the junction for Cox Green and White Waltham, the present 9A on A404(M), fit in? According to some forum entries it was constructed after the rest of the motorway was opened, but the OS 1:25000 on the Sabre Maps shows this section of road as under construction and a junction in exactly the same place as the present one.

The Sabre Wiki doesn't mention the opening date, and neither does Wikipedia.

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wrinkly
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Re: M4 junction numbers

Post by wrinkly »

The junction now known as 9A is original. At least's shown on old-maps 1966. However it's not shown on my 1968 Route Planning Map, which shows no junction numbers west of 8. The terminal junction (which was then an at-grade roundabout) is shown as a numberless junction, whereas 9A is not shown at all. The present 8/9 is also not shown at all.
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DavidB
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Re: M4 junction numbers

Post by DavidB »

I'm sure that the terminal junction was 9B and the fifth post in this thread from 2007 would seem to confirm that:

http://www.sabre-roads.org.uk/forum/vie ... =1&t=17392
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Re: M4 junction numbers

Post by zapalniczka »

DavidB wrote:I'm sure that the terminal junction was 9B and the fifth post in this thread from 2007 would seem to confirm that:

http://www.sabre-roads.org.uk/forum/vie ... =1&t=17392
that would make sense seeing as the M4 was never intended to continue from the original terminus but cut into the motorway at some point. It was originally going to be after 9A and not before; this would have resulted in the numbers around here making sense but the rerouting of the M4 to the south of Reading made a bit of a mess of that.
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Re: M4 junction numbers

Post by Brock »

steve618 wrote:But where does the junction for Cox Green and White Waltham, the present 9A on A404(M), fit in?
A pretty unusual junction by all accounts, since it's with an unclassified road. Why was it deemed necessary? I can't offhand think of any other such junctions on non-urban motorways.
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Re: M4 junction numbers

Post by Chris Bertram »

Brock wrote:I can't offhand think of any other such junctions on non-urban motorways.
M56 J4, north-facing slips only, a junction for Wythenshawe.
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Re: M4 junction numbers

Post by PeterA5145 »

Chris Bertram wrote:
Brock wrote:I can't offhand think of any other such junctions on non-urban motorways.
M56 J4, north-facing slips only, a junction for Wythenshawe.
I suppose you could regard that as urban. M58 J1 is with an unclassified road, although the A506 is close by. M80 J2 as well.
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Re: M4 junction numbers

Post by Chris Bertram »

PeterA5145 wrote:
Chris Bertram wrote:
Brock wrote:I can't offhand think of any other such junctions on non-urban motorways.
M56 J4, north-facing slips only, a junction for Wythenshawe.
I suppose you could regard that as urban. M58 J1 is with an unclassified road, although the A506 is close by. M80 J2 as well.
J9a "feels" urban though, the A404(M) does hug the western edge of Maidenhead pretty closely. I think it's there to siphon off the commuters living there so they don't have to head through the centre of Maidenhead and jam up the A308 heading for the A308(M) to get to the M4 for London. It's certainly a busy enough junction.
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Re: M4 junction numbers

Post by M5Lenzar »

If the original M4 routing came off between 9A and 9B, why build the motorway up to a point beyond where it was going to diverge?
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Re: M4 junction numbers

Post by wrinkly »

You could equally ask, why was the Preston bypass continued to meet the A6 at its north end? Why was the Lancaster bypass continued to meet the A6 at both ends?

One answer is that a motorway ending in the middle of a field isn't much use. :D
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Re: M4 junction numbers

Post by RJDG14 »

Many early motorways did this without any provision as a way to save money. Among the ones you've mentioned we also have solid roundabouts with no flyover stump, including the M4 Crick temporary terminus - A mystery that only existed from 1966 until 1967 when the motorway was extended down into Cardiff. In fact, can anybody think of a list of these (former and new) non-roundabout temporary junctions that are now gone built to easily get traffic off without the road going any further. Here are mine (Without the junction number):

* NI M22 west of Randalstown - Still there

* N1 M2 north of Ballymena - Possibly half built, still there

* M4 Crick - Now gone

* M18 south of western M180 terminus - Now gone

* M57 / M58 Switch Island - Still there

And not to mention the former M2 Paradise Walk terminus!
Last edited by RJDG14 on Tue Jun 04, 2013 18:32, edited 2 times in total.
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Re: M4 junction numbers

Post by wrinkly »

Also, if you haven't built any bridges at the junction with the future mainline, it's less embarrassing if plans change.
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Re: M4 junction numbers

Post by WHBM »

M5Lenzar wrote:If the original M4 routing came off between 9A and 9B, why build the motorway up to a point beyond where it was going to diverge?
The original intention in outline was that the M4 was going to pass to the north of Reading. After the Maidenhead by-pass section was built there was a change of plan and it was rerouted to the south. This accounts for the quite notable change of overall direction from west to south-west at this point. There was also anticipated to be a branch to Oxford; once the reroute was agreed this was impractical and the extension of the M40 onwards to Oxford instead came up the list.
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Re: M4 junction numbers

Post by RJDG14 »

Early plans also show that it may have gone north of Didcot and also Swindon.
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Re: M4 junction numbers

Post by RJDG14 »

wrinkly wrote:Also, if you haven't built any bridges at the junction with the future mainline, it's less embarrassing if plans change.
And that is exactly what went wrong with the Ballymena Bypass. With road building terminating due to the troubles, it was never completed and especially at the north end you are routed round a really strange layout onto the A26. I reacon it was meant to be a large, open plan interchange but it is hard to currently know. The southern end used to be unfinished in roundabout form, with the southern slip roads missing and nothing underneath the bridges but it has more recently been used for another plan, so things sometimes work out.
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Re: M4 junction numbers

Post by Chris Bertram »

RJDG14 wrote:Many early motorways did this without any provision as a way to save money. Among the ones you've mentioned we also have solid roundabouts with no flyover stump, including the M4 Crick temporary terminus - A mystery that only existed from 1966 until 1967 when the motorway was extended down into Cardiff. In fact, can anybody think of a list of these (former and new) non-roundabout temporary junctions that are now gone built to easily get traffic off without the road going any further. Here are mine (Without the junction number):

* NI M22 west of Randalstown - Still there

* N1 M2 north of Ballymena - Possibly half built, still there

* M4 Crick - Now gone

* M18 south of western M180 terminus - Now gone

* M57 / M58 Switch Island - Still there

And not to mention the former M2 Paradise Walk terminus!
There was a temporary terminus of the M40 just west of Beaconsfield on the A40, no evidence of this remains. At the other end, the M40 used to flow seamlessly into the A40 just beyond J7. the A40 has now been diverted away and no evidence remains, apart from the closed west-facing on-slip at J7. From the PoV of westbound traffic, the motorway ended in the middle of nowhere, while for eastbound traffic it began where the A40 diverged about a mile before J7.

Before the Cullompton bypass was absorbed into the M5, there were temporary termini at each end, I think they were roundabouts.

M54 J5 was formerly in a location about 1/2m east of the current junction, when it was the temporary terminus of the Telford section of the motorway. I think it was a west-facing half-diamond interchange with the A5, but there's not much left now.
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Re: M4 junction numbers

Post by Mattemotorway »

Chris Bertram wrote:Before the Cullompton bypass was absorbed into the M5, there were temporary termini at each end, I think they were roundabouts.
My 1974 OS map shows it as having a roundabout at the north end, whilst it just flowed into the old road at the south end...
My old posts are just downright embarrassing.

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Re: M4 junction numbers

Post by wrinkly »

Old-maps.co.uk 1970 1:2500 and 1972 1:10000 show the south end of the Cullompton bypass as a roundabout of somewhat triangular shape.

Edit: here's something I didn't know before. Old-maps 1969-1971 1:2500 shows the north end of the Cullompton bypass as a circular roundabout with splayed carriageways on its southern approach, so when the bypass was designed it must have been intended to become a permanent motorway junction.
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Re: M4 junction numbers

Post by Ritchie333 »

wrinkly wrote:Old-maps.co.uk 1970 1:2500 and 1972 1:10000 show the south end of the Cullompton bypass as a roundabout of somewhat triangular shape.
This lane was one of the arms of the junction. The point at the other end is now on the M5 mainline - the B3181 was rerouted east of the original A38 alignment.
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Re: M4 junction numbers

Post by A303Chris »

WHBM wrote:
M5Lenzar wrote:If the original M4 routing came off between 9A and 9B, why build the motorway up to a point beyond where it was going to diverge?
The original intention in outline was that the M4 was going to pass to the north of Reading. After the Maidenhead by-pass section was built there was a change of plan and it was rerouted to the south. This accounts for the quite notable change of overall direction from west to south-west at this point. There was also anticipated to be a branch to Oxford; once the reroute was agreed this was impractical and the extension of the M40 onwards to Oxford instead came up the list.

That is correct, it was going to go to the south of Henley, past Wallingford , through the vale of White Horse and join up on the existing line at J15.

From my distant past at Berkshire CC in the late 1980's and talking to a former Motorway Construction Unit Engineer there was two reasons why this was not done.

Firstly between Maidenhead and Wallingford meant going through the Chilterns Area of Outstanding Natural Beauty and the proposed alingment would have been very expensive to construct especially around Henley and cause quite a lot of damage to this peaceful area.

The second was that it was away from the majority of large towns and buisness centres and links to places like Reading and Newbury would have been poor.

So the current route was choosen as it was easier to build and cheaper and as a result it went closer to major towns such as Bracknell, Reading and Newbury


With regards the original post i do have maps at home from the 60's which show the junctions as 9a and 9B which carried on being the same when the spur became the A423(M) then the A404(M)
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