Forth Replacement Crossing

[Halmyre]

I came over the bridge (northbound) earlier today and it was fairly free-flowing at ~40mph until you reached the bridge itself (after the on-slip from the A904) at which point the speed dropped to around 30mph or even less. Only when nearly across the bridge did the mass of traffic start to get back up to ~40mph. Similar patterns occur at rush hour. This suggests that people are deliberately driving slowly over the bridge, for whatever reason. They can't still be sight-seeing, surely?

It's the same southbound - there's congestion where the on-slip from Inverkeithing/Royth joins the bridge, but the congestion continues at ~20-30mph until the other end of the bridge, instead of quickly picking up to 40.

Baffling (and frustrating).

[wrinkly]

I was in the area on Monday-Tuesday and drove over it several times both ways. I suspected sightseeing.

[booshank]

Now the replacement crossing is built, wouldn't it make it a lot easier to refurbish the original bridge, say by replacing the cables, if necessary?

Then you'd double the capacity to four lanes per direction.

[GrahameCase]

Now the replacement crossing is built, wouldn't it make it a lot easier to refurbish the original bridge, say by replacing the cables, if necessary?

Then you'd double the capacity to four lanes per direction.

How much would it cost to refurbish though ? The cables are anchored 10s of metres into the rock at either side

[cb a1]

No idea about the cost, but it would be a fascinating engineering project to replace the cables on the existing Forth Road Bridge.

I was told many years ago that the towers are not strong enough to take the weight of a new main cable alongside the existing main cable. I don't know if one main cable is strong enough to hold up the entire bridge by itself.

Back when I heard the information about the towers not being strong enough, it was in respect of the option of refurbishing the bridge vs. building a new one. A time period of 5 years was put on refurbishing the bridge (under a full closure situation). I've no idea how accurate that figure was, but it's certainly not a small task.

[wrinkly]

No idea about the cost, but it would be a fascinating engineering project to replace the cables on the existing Forth Road Bridge.

I was told many years ago that the towers are not strong enough to take the weight of a new main cable alongside the existing main cable. I don't know if one main cable is strong enough to hold up the entire bridge by itself.

I think the towers were strengthened in the 1980s or 90s because of the increasing weight of HGVs and the increasing number of vehicles.

I imagine replacing the main cables would be a huge job by any method. I think it's been done on at least one suspension bridge in the USA by putting in new main cables above the old ones.

Replacing cables on a cable-stayed bridge like the Queensferry Crossing is relatively easy. I think they're designed to stay up (not sure whether trafficked) with any one cable removed.

[Halmyre]

The towers were strengthened in 1998 by inserting steel beams into them; I think it was done from below deck level so that work could be carried out without disrupting traffic.

[fras]

Here is the report on the old bridge suspension cables: -

http://www.gov.scot/Publications/2006/03/03154220/0

Its interesting that there is, apparently, a process and mathematics to work out the degree of loss of strength.

An interesting sentence at the end of APpendix C

"It is irrational to be concerned when a structure which has been designed to be safe after it has deteriorated has indeed deteriorated - unless the deterioration has progressed to such an extent that its reliability is becoming unacceptably low."

[cb a1]

No idea about the cost, but it would be a fascinating engineering project to replace the cables on the existing Forth Road Bridge.

I was told many years ago that the towers are not strong enough to take the weight of a new main cable alongside the existing main cable. I don't know if one main cable is strong enough to hold up the entire bridge by itself.

I think the towers were strengthened in the 1980s or 90s because of the increasing weight of HGVs and the increasing number of vehicles.

This was a discussion about 11 or 12 years ago maybe when the extent of the corrosion was becoming so evident that it was at the 'something must be done' stage. So quite some time after the tower strengthening works.

[Nwallace]

Replacing cables on a cable-stayed bridge like the Queensferry Crossing is relatively easy. I think they're designed to stay up (not sure whether trafficked) with any one cable removed.

I'm sure there was mention of the redundancy level in the cables on the new forth bridge; 2 or 4 possibly?

[Bryn666]

Now the replacement crossing is built, wouldn't it make it a lot easier to refurbish the original bridge, say by replacing the cables, if necessary?

Then you'd double the capacity to four lanes per direction.

How much would it cost to refurbish though ? The cables are anchored 10s of metres into the rock at either side

Given the clue is in the phrase 'Forth Replacement Crossing', the new bridge isn't about capacity, it's about preventing the old bridge falling into the sea through corrosion and fatigue. Plus there's nowhere for the traffic to go at either end so you'd have more congestion with four lanes each way.

[A9NWIL]

At the moment the old bridge is closed for repairs and road resurfacing, so the new bridge is taking all the traffic, but when it re-opens it will apparently be restricted to buses and bicycles, and the new bridge has to take the main traffic flow. This is surely a wanton misuse of a resource. You surely don't have and maintain a huge dual-carriageway suspension bridge to take bus service, even if it is a frequent one. A 10-minute bus service from the P&R plus a few other routes means there will only be about 3-4 buses actually on the bridge at any one time in each direction. I do hope commonsense prevails and that both bridges are used to play their full part in handling the cross-Forth traffic.

If you ignore the fact that the old bridge is falling to bits and can't handle the traffic anymore (hence it's been replaced), then yes, total common sense, until it falls down.

The old bridge is hardly falling down, it was carrying all the traffic until a few days ago ! So lets carry on with a bit more commonsense, shall we ?

Of course the failure of 2015 that cause the bridge to be shut clearly shows there is an issue with some of its structure. And, of course, the old bridge was never built to take the weight of current HGVs. When it was completed in 1964 the maximum weight of HGVs was 28 tonnes. In addition it was based on a maximum traffic flow of 30k vehicles in each direction per day. Current traffic is over double that. Whilst various joints and pins can be replaced, the main issue is the suspension cables. Assessing these is very difficult and if no traffic restrictions were imposed, the life of the bridge would be much reduced. The main cable strength is around 10% reduced. If this can be maintained, and further loss prevented, there is nothing to prevent its use, but with HGVs banned and traffic restricted to be at or below the historical design parameter.

There is a lot of politics in this bridge, but as I understand it, from conversations with our friends in Edinburgh, the bridge may be opened up to local traffic on a registration basis with a toll for un-registered light vehicles, and with a ban of HGVs. There has been a huge row about the new bridge only replacing the old one and with the same capacity so not providing any improvements. Of course there is always the Green Blob screaming and shouting, and Scotland is no different.

So, if things come to pass, a bit like the London Congestion Charge, you would see the Big C sign and then know you needed to pay £10 unless registered. I suspect a fee would be imposed to register, so in effect becomes a season ticket. I would think this a better option than just closing the bridge to all traffic except buses and bikes. For a start-off, it would get some money in for the repairs, but not significantly shorten the life of the bridge.

Thats a sensible option in my opinion, but I dont think tolls on the new bridge would be good. I guess if the tolls were only on the old bridge which would be quiet, some people would see it as a nice short cut but only if free flow links were provided. It would certainly alleviate the issues with excess traffic trying to cross the new bridge.

[A9NWIL]

Now the replacement crossing is built, wouldn't it make it a lot easier to refurbish the original bridge, say by replacing the cables, if necessary?

Then you'd double the capacity to four lanes per direction.

How much would it cost to refurbish though ? The cables are anchored 10s of metres into the rock at either side

Given the clue is in the phrase 'Forth Replacement Crossing', the new bridge isn't about capacity, it's about preventing the old bridge falling into the sea through corrosion and fatigue. Plus there's nowhere for the traffic to go at either end so you'd have more congestion with four lanes each way.

On the south side of the Forth the traffic splits onto both the M90 and the A90 so 4 lanes each way which basically take all the lanes from both the M90 and A90 together makes sense. On the northern side 4 lanes up until the A92 which would again be like 2 D2s splitting/merging would also make sense.

[Mark Hewitt]

Go back to 2009 and the signs said Forth Road Bridge. Nowadays they say Dundee, Perth.

Signs on the M8 still say "Forth Road Bridge (A90)" as of September 2016 - I don't know if have already been changed, or if they will be changed to say "Dundee, Perth (M90)" at some point in the future.

Is that more to do with the removal of tolls? When tolls existed then you needed to know you were being routed over the bridge whereas toll free it’s essentially irrelevant.

[Dunragit]

How much would it cost to refurbish though ? The cables are anchored 10s of metres into the rock at either side

Given the clue is in the phrase 'Forth Replacement Crossing', the new bridge isn't about capacity, it's about preventing the old bridge falling into the sea through corrosion and fatigue. Plus there's nowhere for the traffic to go at either end so you'd have more congestion with four lanes each way.

On the south side of the Forth the traffic splits onto both the M90 and the A90 so 4 lanes each way which basically take all the lanes from both the M90 and A90 together makes sense. On the northern side 4 lanes up until the A92 which would again be like 2 D2s splitting/merging would also make sense.

The A90 isn't a D2 for long though. Adding capacity over the Forth may just shift the bottleneck east. If the A720 were extended from Gogar to meet the A90 before crossing the Almond it might be worthwhile, but that seems reasonably unlikely.

What Transport Scotland want is for public transport to have a clear run over the Forth at all times. The main traffic constraint they're worried about is the City of Edinburgh itself, and the only way of getting enough people in and out of it is for them to be sitting on buses and trains. If more capacity were available over the Forth for road users, it is likely that it would be used up primarily by people driving to and from the city.

Making it easier for Fife-Strathclyde traffic to use the Kincardine/Clackmannanshire bridges seems to me to be an overall better solution. For one, it doesn't help people drive into Edinburgh, and the routes it does help are those with enough road capacity and variety onward connections to handle any increase in traffic. Also, it would keep extra traffic away from the M8, reducing the need to engage in expensive widening or improvement works. It's better to upgrade roads which are currently of relatively low standard than it is to upgrade ones which are already motorways. An upgraded motorway just means more traffic; an improved secondary route means new journey possibilities.

Improved roads on the north bank of the Forth would be easier to justify environmentally too, as they wouldn't be competing against feasible train journeys for commuters. The Airdrie-Bathgate link was implemented as a result of investigations into improving capacity on the M8 corridor, and any further improvements to the road have to be weighed against encouraging people to travel by train. Between Fife and Stirling/Strathclyde people already have to drive as the train is pretty much out of the question now and for the forseeable future.

The first step would obviously be to link the A895 to Pitreavie Roundabout and finish the Rosyth Bypass. It might even happen, given the amount of community support for it.

[A9NWIL]

The A90 isn't a D2 for long though. Adding capacity over the Forth may just shift the bottleneck east. If the A720 were extended from Gogar to meet the A90 before crossing the Almond it might be worthwhile, but that seems reasonably unlikely.

What Transport Scotland want is for public transport to have a clear run over the Forth at all times. The main traffic constraint they're worried about is the City of Edinburgh itself, and the only way of getting enough people in and out of it is for them to be sitting on buses and trains. If more capacity were available over the Forth for road users, it is likely that it would be used up primarily by people driving to and from the city.

Making it easier for Fife-Strathclyde traffic to use the Kincardine/Clackmannanshire bridges seems to me to be an overall better solution. For one, it doesn't help people drive into Edinburgh, and the routes it does help are those with enough road capacity and variety onward connections to handle any increase in traffic. Also, it would keep extra traffic away from the M8, reducing the need to engage in expensive widening or improvement works. It's better to upgrade roads which are currently of relatively low standard than it is to upgrade ones which are already motorways. An upgraded motorway just means more traffic; an improved secondary route means new journey possibilities.

Improved roads on the north bank of the Forth would be easier to justify environmentally too, as they wouldn't be competing against feasible train journeys for commuters. The Airdrie-Bathgate link was implemented as a result of investigations into improving capacity on the M8 corridor, and any further improvements to the road have to be weighed against encouraging people to travel by train. Between Fife and Stirling/Strathclyde people already have to drive as the train is pretty much out of the question now and for the forseeable future.

The first step would obviously be to link the A895 to Pitreavie Roundabout and finish the Rosyth Bypass. It might even happen, given the amount of community support for it.

Well my point is about improving the long distance capabilities.
In that respect extending the A720 to meet the A90 would be a good idea.
Also upgrading it and the small section of A90 that will run between the M90 and A720 to motorway D2M and making it all free flow and free flow into the A1.
Perhaps take the A1 number up to meet the M90 at the A1 (M)?
That would encourage the A1 to perhaps become a motorway all the way from Newcastle to the M90. Which could perhaps become the M1 all the way from Yorkshire to there? That would mean a really good long distance motorway from London to Scotland with good links to all the major roads into Edinburgh.

Then make the new bridge D3 and the old bridge D1 + bus lanes with a weight restriction of up to 7.5 tonnes.

The A90 from Edinburgh could free flow into the old bridge only with the other routes all free flowing onto the new bridge only.

From the north the A90 over the old bridge could be signed as Edinburgh and south Queensferry only with weight restriction fines. It would be a slower route anyway with a 40MPH restriction which would encourage some traffic over the new bridge to get to Edinburgh and Queensferry anyway.

So that would make the new bridge mainly a long distance route, with the old bridge specifically handling more local traffic enforced by road layout.

[fras]

As well as going over the new Forth bridge, (Queensferry crossing), we also went over the old Kincardine bridge of 1936 about four times. It is now restricted to 30 mph and is S2. There is a fairly new bridge very close that takes the A876 around Kincardine so one doesn't have to go through the middle of Kincardine.

However if one wanted to relieve the new bridge of traffic from FIfe wanting to get to Glasgow or nearby the A985 could be usefully diverted in places and improved to connect east at the A823 (M) and west at the north side of Kincardine into the A876. In essence what you'd be doing is giving an alternative to the M90-bridge-M8. I have to say, though that an S2 road as exists now, would not really be suitable, IMHO.

Of course to really make people decide, the reintroduction of bridge tolls needs to be thought about. Once you do this and provide an alternative, it is a simple matter to set the toll to manage the flows.Some people won't pay, others will.

[Burns]

As well as going over the new Forth bridge, (Queensferry crossing), we also went over the old Kincardine bridge of 1936 about four times. It is now restricted to 30 mph and is S2. There is a fairly new bridge very close that takes the A876 around Kincardine so one doesn't have to go through the middle of Kincardine.

I really like the Kincardine Bridge, with its brutal metal rotating section (that doesn't rotate) and those wonderful 30s streetlights. However, thanks to the Clackmannanshire Bridge, it's been a long time since I last drove over the Kincardine Bridge. The needless traffic lights put me off. I understand why they used to be there but their only function now is to delay and annoy. Still, the Clackmannanshire Bridge never has any delays on it so that's my bridge of choice over the Forth.

[Altnabreac]

As well as going over the new Forth bridge, (Queensferry crossing), we also went over the old Kincardine bridge of 1936 about four times. It is now restricted to 30 mph and is S2. There is a fairly new bridge very close that takes the A876 around Kincardine so one doesn't have to go through the middle of Kincardine.

I really like the Kincardine Bridge, with its brutal metal rotating section (that doesn't rotate) and those wonderful 30s streetlights. However, thanks to the Clackmannanshire Bridge, it's been a long time since I last drove over the Kincardine Bridge. The needless traffic lights put me off. I understand why they used to be there but their only function now is to delay and annoy. Still, the Clackmannanshire Bridge never has any delays on it so that's my bridge of choice over the Forth.

The A985 is a pretty good Road from Kincardine to Cairneyhill. A Rosyth Bypass and maybe a bit of WS2+1 plus realignment around Crombie and you'd have a very viable Glasgow - South Fife route.

[Burns]

The A985 is a pretty good Road from Kincardine to Cairneyhill. A Rosyth Bypass and maybe a bit of WS2+1 plus realignment around Crombie and you'd have a very viable Glasgow - South Fife route.

I fully agree. A few tweaks to the A985 would make it a great alternative to Queensferry. I stay in North Fife so I almost always approach Kincardine from the A977 so the Clackmannanshire Bridge is the obvious choice.