1995 plans for Deptford Interchange (A303/A36 near Wylye)

[jackal]

A thread to discuss the above, as redrawn by Truvelo:

Brown option:


Yellow option:


More info: https://www.sabre-roads.org.uk/wiki/ind ... nterchange

[Bryn666]

Both are fairly horrible to be honest.

[jackal]

Yellow is really silly, granted.

I quite like Brown, though. It's similar to a cloverleaf but with three differences:

1. The local access, which most notably fouls up the A36 mainline.
2. A303 wb to A36 eb goes round the houses.
3. A36 eb to A303 wb goes round the outside of the trumpet and down the link road rather than using a loop.

1 is mostly a legacy issue and not really the designers' fault.

2 can maybe be forgiven as it's not a strategically important movement.

3 is actually an improvement on a normal cloverleaf, as it removes the weaving on the westbound A303 that a conventional loop would give you. This modified cloverleaf in Lisbon does something similar: https://www.google.co.uk/maps/@38.74063 ... &entry=ttu

Obviously the weaving on the eastbound A303 is not great, but I can at least see what they were going for given site and budget limitations.

[Gav]

why not go the way they do in the States.... ?

Simple trumpet to trumpet ? job jobbed....

[jackal]

why not go the way they do in the States.... ?

Simple trumpet to trumpet ? job jobbed....

The merge and diverge would be virtually on top of each other. In the US this isn't an issue as there are toll booths in the way.

[Peter Freeman]

^ I've driven through one of those, in Florida, and yes: tolled. But are they all?

[Peter Freeman]

^ I've driven through one of those, in Florida, and yes: tolled. But are they all?

I think I just answered my own question. This unusual double-barrelled one is tolled -
https://www.google.com.au/maps/place/Or ... ?entry=ttu

But this one isn't -
https://www.google.com.au/maps/place/Or ... ?entry=ttu
(but both roads that it connects are).

[jackal]

Indeed, though the second one is built on a rather larger scale than Deptford so there is at least some space between merge and diverge.

[RichardA35]

I'd vote for the "Do Nothing" option.
Was it all really necessary or cost effective when the links between the A36 & A303 carry only about 3,000 vehicles per day?
It might well have ended up looking even more of a white elephant than the current junction.

[Chris5156]

why not go the way they do in the States.... ?

Simple trumpet to trumpet ? job jobbed....

The merge and diverge would be virtually on top of each other. In the US this isn't an issue as there are toll booths in the way.

You’d also have to carry out additional works to accommodate the local road to Wylye that joins the link road. That doesn’t look simple. Closing it would put all traffic between Wylye and Deptford onto the A303, which is probably undesirable.

[Peter Freeman]

I'd vote for the "Do Nothing" option.
Was it all really necessary or cost effective when the links between the A36 & A303 carry only about 3,000 vehicles per day?
It might well have ended up looking even more of a white elephant than the current junction.

Indeed. It must have been built in 'the good old days'. It looks overkill now, yet it was already there in 1985. I can think of half a dozen better and cheaper options, but, since it's there, leave well alone.

[jackal]

I'd vote for the "Do Nothing" option.
Was it all really necessary or cost effective when the links between the A36 & A303 carry only about 3,000 vehicles per day?
It might well have ended up looking even more of a white elephant than the current junction.

Indeed. It must have been built in 'the good old days'. It looks overkill now, yet it was already there in 1985. I can think of half a dozen better and cheaper options, but, since it's there, leave well alone.

The link in the OP says:

A serious of accidents in the early 1990s resulted in the installation of traffic lights and a 50mph speed limit. These measures were intended to be temporary. In 1995 proposals were made to eliminate the right turn by adding additional slip roads to the north side of the junction

I suppose from this that safety was a major consideration.

Also bear in mind that there was a 90s proposal for a long grade-separated DC bypass of Salisbury and the villages between there and Deptford. Though it would apparently have stopped short it would presumably add to demand and the S2 gap may well have been filled before long.



This is again redrawn by Truvelo from the original plans.

[solocle]

I'd vote for the "Do Nothing" option.
Was it all really necessary or cost effective when the links between the A36 & A303 carry only about 3,000 vehicles per day?
It might well have ended up looking even more of a white elephant than the current junction.

Indeed. It must have been built in 'the good old days'. It looks overkill now, yet it was already there in 1985. I can think of half a dozen better and cheaper options, but, since it's there, leave well alone.

The link in the OP says:

A serious of accidents in the early 1990s resulted in the installation of traffic lights and a 50mph speed limit. These measures were intended to be temporary. In 1995 proposals were made to eliminate the right turn by adding additional slip roads to the north side of the junction

I suppose from this that safety was a major consideration.

Also bear in mind that there was a 90s proposal for a long grade-separated DC bypass of Salisbury and the villages between there and Deptford. Though it would apparently have stopped short it would presumably add to demand and the S2 gap may well have been filled before long.



This is again redrawn by Truvelo from the original plans.

Curious that Old Shaston Drove shows on that map (north of Coombe Bissett).

[RichardA35]

I'd vote for the "Do Nothing" option.
Was it all really necessary or cost effective when the links between the A36 & A303 carry only about 3,000 vehicles per day?
It might well have ended up looking even more of a white elephant than the current junction.

Indeed. It must have been built in 'the good old days'. It looks overkill now, yet it was already there in 1985. I can think of half a dozen better and cheaper options, but, since it's there, leave well alone.

The link in the OP says:

A serious of accidents in the early 1990s resulted in the installation of traffic lights and a 50mph speed limit. These measures were intended to be temporary. In 1995 proposals were made to eliminate the right turn by adding additional slip roads to the north side of the junction

I suppose from this that safety was a major consideration.

Also bear in mind that there was a 90s proposal for a long grade-separated DC bypass of Salisbury and the villages between there and Deptford. Though it would apparently have stopped short it would presumably add to demand and the S2 gap may well have been filled before long.
..snip..

Yes I realise the context and the junction scheme was only really a possibility for a couple of years in the mid-1990s.
With the political will at the time to make the A303 entirely a dual carriageway (expressway anyone? ), the long distance demand was baked into the various A303 scheme forecasts. For the A36, as noted, the will was to have a programme of schemes to link up to the Salisbury Bypass but once that failed to progress via the Wessex Link DBFO, this scheme was dead in the water and, with the change in government, the A36 was slated for detrunking and funding seemingly reduced to minimum care and maintenance levels.

[Big L]

…
A serious of accidents
…

Is that a new collective noun?

[Gaz909909]

I'd vote for the "Do Nothing" option.
Was it all really necessary or cost effective when the links between the A36 & A303 carry only about 3,000 vehicles per day?
It might well have ended up looking even more of a white elephant than the current junction.

Indeed. It must have been built in 'the good old days'. It looks overkill now, yet it was already there in 1985. I can think of half a dozen better and cheaper options, but, since it's there, leave well alone.

The link in the OP says:

A serious of accidents in the early 1990s resulted in the installation of traffic lights and a 50mph speed limit. These measures were intended to be temporary. In 1995 proposals were made to eliminate the right turn by adding additional slip roads to the north side of the junction

I suppose from this that safety was a major consideration.

Also bear in mind that there was a 90s proposal for a long grade-separated DC bypass of Salisbury and the villages between there and Deptford. Though it would apparently have stopped short it would presumably add to demand and the S2 gap may well have been filled before long.



This is again redrawn by Truvelo from the original plans.

Now that's what I'm talking about. This would literally shave about 15-20 mins off journey time along the A36 and to be honest, brings this route to A303 as a serious contender over A31/A35 Southampton to Exeter...

[RichardA35]

Now that's what I'm talking about. This would literally shave about 15-20 mins off journey time along the A36 and to be honest, brings this route to A303 as a serious contender over A31/A35 Southampton to Exeter...

The questions remain pretty much as 25 years ago, the journey time benefit is at what cost of construction, at what cost to the environment and the economic benefit is for how many people or how much freight? Previously the costs outweighed the benefits and as the A36 is a marginally strategic route, I'm unsure whether anything has changed that would make the proposals more attractive. I suspect it is unlikely we will see any of this built.

[Gaz909909]

In reality the large housing estates that have since sprung up in Salisbury (especially the one to the north) make this all but impossible. But it would be nice....

[Bryn666]

Now that's what I'm talking about. This would literally shave about 15-20 mins off journey time along the A36 and to be honest, brings this route to A303 as a serious contender over A31/A35 Southampton to Exeter...

The questions remain pretty much as 25 years ago, the journey time benefit is at what cost of construction, at what cost to the environment and the economic benefit is for how many people or how much freight? Previously the costs outweighed the benefits and as the A36 is a marginally strategic route, I'm unsure whether anything has changed that would make the proposals more attractive. I suspect it is unlikely we will see any of this built.

The problem we have is we only build "bypasses" to allow more housing and tin sheds to be built, we never build bypasses to take traffic off existing unsuitable roads.

[Truvelo]

Virtually the entire length of A36 was planned to be upgraded at the time. Just to the west of Deptford was this proposal.

https://www.sabre-roads.org.uk/wiki/ind ... nterchange