Motorway junctions or bridges that were built prior to their road

[RJDG14]

A portion of the 1986 mapping of Swanley Interchange is found on the BBC Domesday Book that shows the interchange open without the freeflowing slips before the Swanley to Sevenoaks section opened.

A further series of "1990" dated aerial photos is available on the Kent CC GIS system here. (select map views, and the 1990 dated aerial photograph layer, then zoom to required area)

The M25 there opened in 1986 so the map extract would have been out of date. At the very least, it should have shown the M25 south of jnc 3 under construction. Certainly inconclusive as to whether the direct slips would have been open.

It was likely the most recent OS revision at the time of the project.

[RJDG14]

One low resolution USGS image from 1978 suggests that there was about a mile of M42 immediately north of J4 of the M6 which had been built but wasn't open at the time as it was a dead end.

[Bryn666]

One low resolution USGS image from 1978 suggests that there was about a mile of M42 immediately north of J4 of the M6 which had been built but wasn't open at the time as it was a dead end.

Yes, this unused bit was sometimes used as NEC overspill from what I've heard.

[Steven]

One low resolution USGS image from 1978 suggests that there was about a mile of M42 immediately north of J4 of the M6 which had been built but wasn't open at the time as it was a dead end.

Yes, this unused bit was sometimes used as NEC overspill from what I've heard.

Yes, up to and including the bridge over the River Cole.

[Ruperts Trooper]

One low resolution USGS image from 1978 suggests that there was about a mile of M42 immediately north of J4 of the M6 which had been built but wasn't open at the time as it was a dead end.

Yes, this unused bit was sometimes used as NEC overspill from what I've heard.

Yes it was used for the car park when the UK Motor Show moved to the NEC from Earls Court, including the use of shuttle buses.

[RichardA35]

I also used it to cycle to work in summer 1985.

[solocle]

Well, the M49 certainly exists, but approaching 5 years on and still no connecting roads at J1.

[wallmeerkat]

Well, the M49 certainly exists, but approaching 5 years on and still no connecting roads at J1.
<trimming the nice photos>

Really don't understand this, the authority built the junction, the developers of the industrial estate would only need to build 150 metres of road to connect to it, what is preventing this? Traffic would currently either join the motorway network at Avonmouth, or continue up the Severn Road to the M48 / Severn Bridge

[Bryn666]

Well, the M49 certainly exists, but approaching 5 years on and still no connecting roads at J1.
<trimming the nice photos>

Really don't understand this, the authority built the junction, the developers of the industrial estate would only need to build 150 metres of road to connect to it, what is preventing this? Traffic would currently either join the motorway network at Avonmouth, or continue up the Severn Road to the M48 / Severn Bridge

It's been covered elsewhere but basically political Shenanigans seem to be to blame.

[ForestChav]

It wouldn't take a lot of effort to connect that up given there's only a small distance of road to make up between the motorway and the estate roads.

Actually the whole area around the M49 is a bit of a mess. So the lack of the intermediate junction does mean all the industrial estate traffic which is right next to a motorway needs to connect to the network either at the M5 at Avonmouth or head to the M48 at Aust.

So it would potentially be beneficial for the motorway to connect to the estate traffic at the unfinished junction, but this would no doubt also lead to other traffic needing to cut through the industrial estate to connect to the A403, which would be another bottleneck potentially.

Admittedly going to either Avonmouth or Aust to connect to a motorway isn't ideal and in the former case puts plenty more strain onto the M4/M5 (e.g. for traffic heading into South Wales, which would also there have to go via Chepstow) but also the whole area is badly connected in general.

Both ends of the M48 linking to the M4 are one way junctions, so in the event the M48 bridge is closed, this means extra faff for traffic having to divert onto the M4 to cross the river. So if the M48 was closed traffic heading from Chepstow into England would need to head west on the M48 then onto the M4, exit at Magor then turn round back onto the M4 and over the river. If they were then wanting to head somewhere like Aust, they would then either have to head to Almondsbury, down the M5 and off into Avonmouth then head back up the A403, or do the same with the M49. Yet this would be adjacent junctions on the M48. If the M48 linked with the M4 at trumpets or another full flow access then at least it would be possible to swap from one motorway to the other no matter what. And it would be in the case of contingency and a road closure where you'd need to do this easily. In regards to the A403 this really does need better connections than the M48 and M5, it completely ignores the M4 and M49 even though it crosses over not too far away from where they meet. I suppose even a diamond interchange with the M49 where the A403 crosses it would be potentially too close to the slip road to cause weaving issues, but actually, this is a roundabout junction with the M4 anyway, so that might not be too bad, but maybe tricky for traffic wanting the M4 eastbound from the A403. It would be possible to pop a link road from the north side of the roundabout which would probably need to run reasonably close and parallel to the M4 because of existing settlement north of the motorway to link to the A403 which might improve this access.

Difficult to see what could otherwise be done with the missing junction though - there's not a lot to the East, but the stub on the island suggests that there was plans to do something there. As for the west side, well it would probably need improvements on the local road network to connect to the A403 a bit better, which would require swerving or moving existing premises so unlikely to happen. So it would remain to just better connect the industrial units to the motorways. Given how busy Aust gets at peak times even though it's not the M4 any longer, this could well help.

[Bryn666]

The industrial estate roads are huge and currently house lots of overnight lorry parking. There's no issue with connections to the A403 beyond bloody mindedness in the hands of developers and local and trunk highway authorities. The failure to complete this road is purely political and nothing to do with engineering problems.

[solocle]

Well, the M49 certainly exists, but approaching 5 years on and still no connecting roads at J1.
<trimming the nice photos>

Really don't understand this, the authority built the junction, the developers of the industrial estate would only need to build 150 metres of road to connect to it, what is preventing this? Traffic would currently either join the motorway network at Avonmouth, or continue up the Severn Road to the M48 / Severn Bridge

It's been covered elsewhere but basically political Shenanigans seem to be to blame.

South Glos have a page about it here. M49 link road
They have planning permission and works are due to start this year, but sounds like they still need to acquire the land!

[WHBM]

Simplistically, the "unfinished" new junction seems to have been built in the wrong place. Even if connected up it would only go into the back of the industrial estate, with no obvious route onwards. If it had been built 1/4 mile south, just where the south-facing slips merge in, there is a direct straight road, Central Avenue, with no frontages, to the A403.

Criticism of the industrial estate owners for not linking it up, but if I were them I would not want to do so either, and have through traffic weaving through my industrial area. However did it get past planning permission ? I thought that was what planning permission was meant to be about.

[RichardA35]

Simplistically, the "unfinished" new junction seems to have been built in the wrong place.

It was the right place if it was wanted to incorporate an existing bridge into the junction. If built elsewhere there would have to have been two new bridges not just one and hence more expensive.

[WHBM]

Simplistically, the "unfinished" new junction seems to have been built in the wrong place.

It was the right place if it was wanted to incorporate an existing bridge into the junction. If built elsewhere there would have to have been two new bridges not just one and hence more expensive.

You're right, of the two bridges one is open abutment, one is closed abutment. Never noticed. Which is the old one ? I actually can't think of another roundabout motorway junction, symmetrical in plan view, where the two bridges are of different basic construction. is it unique ?

And whatever was the purpose of the original bridge on its own ?

[Chris5156]

Simplistically, the "unfinished" new junction seems to have been built in the wrong place.

It was the right place if it was wanted to incorporate an existing bridge into the junction. If built elsewhere there would have to have been two new bridges not just one and hence more expensive.

You're right, of the two bridges one is open abutment, one is closed abutment. Never noticed. Which is the old one ? I actually can't think of another roundabout motorway junction, symmetrical in plan view, where the two bridges are of different basic construction. is it unique ?

And whatever was the purpose of the original bridge on its own ?

The open abutment one is original to the motorway. It carried a public footpath/bridleway, which is now accommodated on the new bridge.

[Bryn666]

Simplistically, the "unfinished" new junction seems to have been built in the wrong place.

It was the right place if it was wanted to incorporate an existing bridge into the junction. If built elsewhere there would have to have been two new bridges not just one and hence more expensive.

You're right, of the two bridges one is open abutment, one is closed abutment. Never noticed. Which is the old one ? I actually can't think of another roundabout motorway junction, symmetrical in plan view, where the two bridges are of different basic construction. is it unique ?

And whatever was the purpose of the original bridge on its own ?

I raise you M61 J9 and M62 J8 as other examples of roundabout interchanges where one of the bridges is the original (although in M61 J9's case the 'original' bridge was built later than the motorway itself as well).

[wrinkly]

I raise you M61 J9 and M62 J8 as other examples of roundabout interchanges where one of the bridges is the original (although in M61 J9's case the 'original' bridge was built later than the motorway itself as well).

And the junction that is now A1307/A141 at Huntingdon which was once a diamond.

Not quite the same is this roundabout which was first opened with the roundabout sitting on the eastern bridge and a temporary embankment at the western side, though the western bridge was planned from the start.

The interim layout existed for about a year in 1974-5 when there was a short gap in the M56 Sharston branch filled by the A560.

[Chris5156]

And the junction that is now A1307/A141 at Huntingdon which was once a diamond.

The Stoneleigh junction on the A46 is undergoing the same treatment now.

[SouthWest Philip]

And the junction that is now A1307/A141 at Huntingdon which was once a diamond.

The Stoneleigh junction on the A46 is undergoing the same treatment now.

There must be quite a list of second bridges added junctions. The A303/A342 at Andover is another.

Conversely there are junctions where 'upgrades' have seen two bridges replaced with one such as M1 jnc 15, M5 jnc 12, M6 jnc 20.