Portishead reopening - speculative / suggestions thread.

[AlastairFraser]

So firstly, Sea Mills and Pill are in no way opposite each other, so exactly where do you want this foot tunnel?

I’ll assume it’s Pill to somewhere around Portway Park & Ride, as there is no population opposite Sea Mills, so I can’t see what possible purpose that would serve.

One minor challenge of a tunnel between Pill and Portway P&R might just be the presence of an existing cycleway and footpath crossing the Avon just a stone’s throw away. Now admittedly the M5 crossing is not that attractive for walkers, and even for cyclists is a bit of a climb, but then a tunnel will have to have to be around 15m deep, so hardly a level route for cyclists either.

I have no idea how much such a tunnel would cost, but I can imagine there are numerous better things to spend the money on. And bearing in mind that one portal of the tunnel would be in North Somerset, where active travel has an exceptionally bad reputation after the council has spend millions on misguided bus lanes and an atrocious revamp of Clevedon sea front which is universally despised, and going to be partially reversed at even more cost to council tax payers.

I was proposing Pill to Shirehampton. It wouldn't be ideal, but it seems there is a shortage of suitable Avon crossing routes in the area.

Unless I'm missing something, a pedestrian tunnel wouldn't serve Portishead so while it would do wonders for connectivity in Pill, you'd still have the question of how to improve transport to Portishead.

I was proposing this in addition to the railway reopening.

While I am all for active travel, there must be far more "profitable" ways to spend the transport budget in the area.
One thing which hasn't been mentioned is the tidal range there... If the railway already gets closed because of flooding at Sea Mills, how high will the tunnel access shafts have to be to keep it safe?

Fair point re flooding - you may need some pumps, but that wouldn't be good for the ongoing maintenance side of the financials.

 

[AndrewE]

Fair point re flooding - you may need some pumps, but that wouldn't be good for the ongoing maintenance side of the financials.

no, I wasn't imagining continuing slow infiltration, but the deluge which would result from the tide being higher than the tunnel entrance... No pumps could deal with that!

 

[AlastairFraser]

no, I wasn't imagining continuing slow infiltration, but the deluge which would result from the tide being higher than the tunnel entrance... No pumps could deal with that!

Oh, then a tunnel entrance slightly further inland would help with that issue.

 

[Tomos y Tanc]

Quite, and it is still an easy walk for a large chunk of Portishead’s population, including all the new Marina development. Which is what is important, as outbound commuter traffic is the key driver of the project.

Yeah, but are you going to get substantial commuter traffic with a 1tph service? The problem with this project has always been that a reasonably frequent service is too expensive while an affordable service would be unattractive to passengers.

I'd love to know how much public money has been blown on a possible Portishead reopening with nothing tangible to show for it.

 

[zwk500]

Oh, then a tunnel entrance slightly further inland would help with that issue.

Have you ever been to the area in question? The relief of the land is not gentle. It is, after all, a gorge.
'Slightly further inland' could mean massive extensions to the gradients.

 

[AlastairFraser]

Have you ever been to the area in question? The relief of the land is not gentle. It is, after all, a gorge.
'Slightly further inland' could mean massive extensions to the gradients.

Yes, I have been.
By "slightly further" I mean a tunnel entrance by the Duke of Cornwall pub in, as opposed to on Marine Parade, and close to the Lamplighters pub on the Shirehampton side.

 

[simonw]

Yes, I have been.
By "slightly further" I mean a tunnel entrance by the Duke of Cornwall pub in, as opposed to on Marine Parade, and close to the Lamplighters pub on the Shirehampton side.

Might as well get a man and a row boat for all the traffic it would generate.

 

[AlastairFraser]

Might as well get a man and a row boat for all the traffic it would generate.

I like your optimism

 

[The exile]

I like your optimism

Presumably, given the fact that there used to be a ferry and there now isn’t, I suspect “over optimistic” is about right.

 

[AlastairFraser]

Presumably, given the fact that there used to be a ferry and there now isn’t, I suspect “over optimistic” is about right.

Never say never...

 

[zwk500]

Yes, I have been.
By "slightly further" I mean a tunnel entrance by the Duke of Cornwall pub in, as opposed to on Marine Parade, and close to the Lamplighters pub on the Shirehampton side.

The Duke of Cornwall is basically at Mean High Tide. Its also less than 50m from the river. I don't know what cycle ramp gradients are permitted these days but wheelchair accessible ramp certainly wouldnt fit in a straight line. You'd need to take out their beer garden out front, then Lowe a spiral ramp some 15m or more to get under the riverbank, and then add some form of flooding prevention on top.
Similar on the other side.

 

[John R]

The Duke of Cornwall is basically at Mean High Tide. Its also less than 50m from the river. I don't know what cycle ramp gradients are permitted these days but wheelchair accessible ramp certainly wouldnt fit in a straight line. You'd need to take out their beer garden out front, then Lowe a spiral ramp some 15m or more to get under the riverbank, and then add some form of flooding prevention on top.
Similar on the other side.

Imagine the mess caused by a worksite big enough to get a small TBM in to bore the tunnel too.

 

[yorksrob]

. But rules are rules I'm afraid, and far be it for us to question the ORR's approach.

The ORR imposes a lot of questionable rules on the railway presently.

ORR should be made to justify its decisions against alternative mitigations.

 

[Mordac]

The ORR imposes a lot of questionable rules on the railway presently.

ORR should be made to justify its decisions against alternative mitigations.

They don't have any incentive to. The legislation should be changed to a cost benefit analysis is used instead of ALARP.

 

[WesternBiker]

Imagine the mess caused by a worksite big enough to get a small TBM in to bore the tunnel too.

Indeed. Option appraisal to replace the ageing Cumberland Basin road bridges rejected a tunnel because it was six times the cost of a bridge...

 

[JKF]

Cable car then? London has one that doesn’t get a lot of use.

 

[Tomos y Tanc]

Cable car then? London has one that doesn’t get a lot of use.

How about a zip-wire?

Tunells are ludicrously expensive things. The mouth of the river Ely in Cardiff has an existing, bricked-up, tunnel under it but when the council costed a re-opening it found that it was cheaper to build a footbridge.

 

[Ashley Hill]

Are we not pro-railway being the enthusiasts we are? Should we not be supporting the reopening of this branch and not coming up with alternative schemes instead?

 

[yorksrob]

How about a zip-wire?

Tunells are ludicrously expensive things. The mouth of the river Ely in Cardiff has an existing, bricked-up, tunnel under it but when the council costed a re-opening it found that it was cheaper to build a footbridge.

How about a hyper-hot air balloon loop ?

 

[AlastairFraser]

The Duke of Cornwall is basically at Mean High Tide. Its also less than 50m from the river. I don't know what cycle ramp gradients are permitted these days but wheelchair accessible ramp certainly wouldnt fit in a straight line. You'd need to take out their beer garden out front, then Lowe a spiral ramp some 15m or more to get under the riverbank, and then add some form of flooding prevention on top.
Similar on the other side.

It's a solution perhaps worth considering, once the railway is open. The traffic volumes on the M5 over the Avonmouth Bridge are already quite high, and, at some point, something is going to have to be done to relieve it. Local traffic is relatively low hanging fruit.

 

[Stephen42]

The ORR imposes a lot of questionable rules on the railway presently.

ORR should be made to justify its decisions against alternative mitigations.

The ORR frequently justifies or explains the basis for its thinking. Taking the Quays Avenue level crossing in Portishead this letter was sent to the project manager explaining the reasons why they would be minded to object to any application.

It's a long letter which has been scanned so won't type out in full, the key reasons are "Exceptional circumstances not demonstrated sufficiently", "Other viable options exist" and "Significant traffic issues would cause safety risks to operation of the railway". The last goes into some detail around likelihood of traffic blocking the crossing and other operational risks.

That the highway authority for the relevant road would be minded to lodge objections on similar traffic grounds suggests the ORR aren't being unnecessarily picky.

 

[Meerkat]

If you really wanted a foot/cycle route across around Pill-Shirehampton you would just build an opening bridge wouldn’t you? Far more attractive to use, and with some fancy design they can be landmarks and visitor attractions. But it would only really be useful for Pill, and make the Portishead line even less viable.

 

[AlastairFraser]

If you really wanted a foot/cycle route across around Pill-Shirehampton you would just build an opening bridge wouldn’t you? Far more attractive to use, and with some fancy design they can be landmarks and visitor attractions. But it would only really be useful for Pill, and make the Portishead line even less viable.

Maybe a cable car is more suitable for that route, if you were intending to cover operating expenses and maintenance (commuter fares could be made available for locals too).

 

[Meerkat]

Maybe a cable car is more suitable for that route, if you were intending to cover operating expenses and maintenance (commuter fares could be made available for locals too).

Why - would it be any cheaper to build? A lot more expensive to operate and slower, and if you charge then it wont get used as much.
For the hypothetical bridge I would hope that it was possible to build it so that it could not be too steep and still let the majority of boats go under without opening - how much goes up/down the river that needs a bridge to open?
Anyway its not going to happen, certainly not unless the railway gets cancelled....though I fear this line is another example of rail theoretically being the answer, but then rail being rail so the possible output becoming so sub-optimal that it isn't worth the ever-escalating cost.

 

[zwk500]

For the hypothetical bridge I would hope that it was possible to build it so that it could not be too steep and still let the majority of boats go under without opening - how much goes up/down the river that needs a bridge to open?

An important point to bear in mind is that there are moorings in Pill Creek, and @AlastairFraser's proposed site is straight throug a sailing club on the Gloucestershire bank. (The Severn is top Left, bristol bottom right on this image).

On the shirehampton side, shifting the bridge and slipway around to get the bridge upriver of the slipway should be easy enough, but moving the bridge to the other side of the creek on the Somerset bank isn't as there are houses right on the bank.

Therefore, any bridge would need to balance the clearance against the likely require openings for boat traffic. And also the operating costs for such openings. I don't know how many boats moored in Pill Creek are masted, but given the other bridges in Bristol itself I'd probably go for a 4.5-5m clearance above high water, which given the width of the river at this point shouldn't be too steep to provide over the navigable channel. https://www.bristol.gov.uk/resident...vigation-in-the-harbour-and-bridge-clearances

However, as a comparison, the new Govan-Partick Bridge in Glasgow that opened recently has a moving span of 99m and cost nearly £30m. https://www.bbc.co.uk/news/articles...an-Partick bridge,and cycle bridges in Europe.

 

[Meerkat]

An important point to bear in mind is that there are moorings in Pill Creek, and @AlastairFraser's proposed site is straight throug a sailing club on the Gloucestershire bank. (The Severn is top Left, bristol bottom right on this image).
View attachment 167158
On the shirehampton side, shifting the bridge and slipway around to get the bridge upriver of the slipway should be easy enough, but moving the bridge to the other side of the creek on the Somerset bank isn't as there are houses right on the bank.

Therefore, any bridge would need to balance the clearance against the likely require openings for boat traffic. And also the operating costs for such openings. I don't know how many boats moored in Pill Creek are masted, but given the other bridges in Bristol itself I'd probably go for a 4.5-5m clearance above high water, which given the width of the river at this point shouldn't be too steep to provide over the navigable channel. https://www.bristol.gov.uk/resident...vigation-in-the-harbour-and-bridge-clearances

However, as a comparison, the new Govan-Partick Bridge in Glasgow that opened recently has a moving span of 99m and cost nearly £30m. https://www.bbc.co.uk/news/articles/c24pm9zjq20o#:~:text=A new Govan-Partick bridge,and cycle bridges in Europe.

An Avon bridge opening section wouldn’t even need to be half that length, but the Pill geography is an issue.
So changed the plan - convert the Portishead line to a busway avoiding the M5 junction, with an opening bridge downstream of Pill to the Portway Parkway station. Rather than a slow infrequent train you get frequent buses along the Portway direct into the city with connections at the P&R for Avonmouth and the railway. These crayons are on fire!

 

[zwk500]

An Avon bridge opening section wouldn’t even need to be half that length, but the Pill geography is an issue.

No, but the majority of the cost will be the fact it swings. £20m is not out of the question for a bridge at Pill.

So changed the plan - convert the Portishead line to a busway avoiding the M5 junction, with an opening bridge downstream of Pill to the Portway Parkway station. Rather than a slow infrequent train you get frequent buses along the Portway direct into the city with connections at the P&R for Avonmouth and the railway. These crayons are on fire!

And where does the freight go? At least a tram-train proposal routed via Wapping Wharf (if you want your Crayons to *really* go doesn't stop the Portbury Docks heavy rail freight.

Although apologies mods we're not extremely far from the topic.

 

[JKF]

There’s already a cycle link between Pill and Shirehampton, over the Avonmouth Bridge. It was one of the reasons why they closed down the ferry in the first place, although not many would bother walking it as it’s a very long way and quite a steep access ramp on the Pill side!

There was always rivalry between the two villages, fights on the ferry and in my day fights on the bridge (although somewhat embellished in the narrations of school friends). I think some locals would view the idea of a tunnel the same way they’d view a portal to Hell.

I did wonder if they could build a more direct ramp up on to the Avonmouth bridge and down to the Parkway station on the other side, but given current access standards the ramp would probably stretch half way to Bristol! Plus I think the bridge deck does move a bit under load/high winds so would need a flexible connection/movement joint of some kind.

 

[AlastairFraser]

There’s already a cycle link between Pill and Shirehampton, over the Avonmouth Bridge. It was one of the reasons why they closed down the ferry in the first place, although not many would bother walking it as it’s a very long way and quite a steep access ramp on the Pill side!

There was always rivalry between the two villages, fights on the ferry and in my day fights on the bridge (although somewhat embellished in the narrations of school friends). I think some locals would view the idea of a tunnel the same way they’d view a portal to Hell.

I did wonder if they could build a more direct ramp up on to the Avonmouth bridge and down to the Parkway station on the other side, but given current access standards the ramp would probably stretch half way to Bristol! Plus I think the bridge deck does move a bit under load/high winds so would need a flexible connection/movement joint of some kind.

Perhaps the ramp you describe could be built and the path across the bridge upgraded + enclosed. The non-motorised user access across the west of the WECA area is poor-quality and needs upgrading at some point.

 

[JKF]

A little bird told me that the full business case was submitted last week, has this been reported anywhere?