Re-doubling of single track lines or reinstatement of passing loops

[zwk500]

Yes they are transposed, because the overall layout was effectively rearranged through Rugby so that the down fast line runs between the two slow lines that go through platforms 1 and 2. It’s been mentioned a few times in these forums that if Brinklow to Nuneaton was ever to get the missing fourth line installed there’d be a need to untangle the down lines somehow, which might actually need another flyover. The roughly 6 mile stretch of single line effectively acts a flat crossover for the slow line traffic to switch sides.

You could probably fiddle with the layout at the North end of Rugby Station to avoid an additional flyover, but that's getting into speculative territory.

 

[Whistler40145]

IIRC the remodelling was sponsored by Inter City and its purpose, apart from simplifying the layout, was to increase speeds on the main line.

How long were services diverted either via Whifflet to Motherwell or via the Glasgow and South Western line?

 

[Woolos 22]

Crosskeysr to llanhillith track has been laid with some gap and no points been there a few years hope to be in used in 2023

 

[Railcar]

With a 'cancer hub' and a new high school being built near to Belmont station (on the line from Sutton to Epsom Downs) a re-doubling of the track from Sutton to Belmont (with a reversing loop laid over Banstead Downs) has been proposed.

 

[zwk500]

With a 'cancer hub' and a new high school being built near to Belmont station (on the line from Sutton to Epsom Downs) a re-doubling of the track from Sutton to Belmont (with a reversing loop laid over Banstead Downs) has been proposed.

At Sutton, where do these extra trains intend to go?

 

[steamybrian]

For Thameslink services-

Borough Market Jn - Metropolitan Jn increased from 2 to 4 tracks.
Metropolitan Jn- Blackfriars line reinstated to double track (if my memory is correct!)

 

[Dr Hoo]

How long were services diverted either via Whifflet to Motherwell or via the Glasgow and South Western line?

The Newton re-modelling was spread over several stages and weeks (I.e. not just weekends) so it definitely fell into the ‘weeks’ category but not something like a complete timetable period.

It is widely misunderstood that the ‘single line’ for the local services was to save a few yards of track. The main line realignment was so significant (to give the desired speed) that there was only enough space left within the BR boundary for one other line.

The subsequent ‘re-doubling’ required a lot of complex and expensive legal procedures to buy a strip of land under Scots property law that I won’t attempt to explain. For obvious reasons these were undertaken extremely discreetly.

 

[Taunton]

It is widely misunderstood that the ‘single line’ for the local services was to save a few yards of track. The main line realignment was so significant (to give the desired speed) that there was only enough space left within the BR boundary for one other line.

It would of course be interesting to see the Risk Assessment associated with the Newton realignment and its associated extension of conflicts on secondary routes. I presume one was done. Was it read out at the enquiry?

 

[MadMac]

Isn't the Hairmyres loop too short to be called a dynamic loop? Or does dynamic loop mean something different from what I thought?

That’s what it was described as in 1990, when they were a fairly new thing. The meaning has evolved over the years.

 

[Dr Hoo]

It would of course be interesting to see the Risk Assessment associated with the Newton realignment and its associated extension of conflicts on secondary routes. I presume one was done. Was it read out at the enquiry?

The Newton Inquiry Report discusses this question at length. Basically 'risk analysis' or 'risk assessment' was not generally undertaken for new layouts. As part of the Inquiry no fewer than three analyses were undertaken after the event.

Prior to the collision BR were relying on the "belief that any layout can be signalled in compliance with BR's signalling principles" (para 320) and the fact that the HMRI Inquiry into the earlier Bellgrove collision had concluded (para 129) that single lead junctions "are acceptable in principle on safety grounds".

Newton was a seminal event. A very great deal changed afterwards, both within BR and in HMRI. Sadly not enough to prevent subsequent events such as Cowden.

 

[Railcar]

With a 'cancer hub' and a new high school being built near to Belmont station (on the line from Sutton to Epsom Downs) a re-doubling of the track from Sutton to Belmont (with a reversing loop laid over Banstead Downs) has been proposed.

At Sutton, where do these extra trains intend to go?

Down to Belmont and round the loop and back to Sutton (and Victoria)

 

[Ken H]

What is the definition of dynamic loop?

At a normal passing loop if trains are to cross there they are cautioned before entering the loop to stop the risk of runnjng theough onto the next single line section.
A dynamic loop has a proper overlap between the exit signals and the points and maybe even trap points, so trains can pass at line speed.
Is that about right???

 

[Falcon1200]

How long were services diverted either via Whifflet to Motherwell or via the Glasgow and South Western line?

I was racking my brains to recall how the job was done, so thanks to @Dr Hoo for his response ! I do remember that the work was indeed done in stages, leading to some 'interesting' train service patterns; For a while, when the main lines through Newton were blocked, a through service operated between Glasgow Central High Level and Dalmuir, via Kirkhill, Hamilton, Motherwell and the Whifflet/Sunnyside (normally) non-passenger route. No Drivers had route knowledge throughout so there were multiple changes, which in some cases became ridiculous; I recall some trains having relief at Newton, Motherwell, Shettleston and Hyndland. If just one of those Drivers was out of place the service collapsed, and I remember Saturdays being especially bad; It was a Controller's nightmare !

It would of course be interesting to see the Risk Assessment associated with the Newton realignment and its associated extension of conflicts on secondary routes.

Basically 'risk analysis' or 'risk assessment' was not generally undertaken for new layouts.

When Control first saw the proposed new layout my concern was reliability at the Glasgow end single lead, more experienced Controllers said it was a recipe for disaster. Sadly it did not take long for their fears to be realised. Thankfully things are different now, both at Newton and more generally.

 

[Dr Hoo]

I was racking my brains to recall how the job was done, so thanks to @Dr Hoo for his response ! I do remember that the work was indeed done in stages, leading to some 'interesting' train service patterns; For a while, when the main lines through Newton were blocked, a through service operated between Glasgow Central High Level and Dalmuir, via Kirkhill, Hamilton, Motherwell and the Whifflet/Sunnyside (normally) non-passenger route. No Drivers had route knowledge throughout so there were multiple changes, which in some cases became ridiculous; I recall some trains having relief at Newton, Motherwell, Shettleston and Hyndland. If just one of those Drivers was out of place the service collapsed, and I remember Saturdays being especially bad; It was a Controller's nightmare !

Ah, yes. I remember the interesting experience of catching a through train in 'normal' service from Central to Queen Street via the route that you describe. My memory is slightly different - that Motherwell drivers were relieved by Yoker at Blairhill, as soon as they had 'set foot' on the sacred eastern side of North Electrics (which only Yoker signed) but I may have that bit wrong.

 

[MarkyT]

The Newton Inquiry Report discusses this question at length. Basically 'risk analysis' or 'risk assessment' was not generally undertaken for new layouts. As part of the Inquiry no fewer than three analyses were undertaken after the event.

Prior to the collision BR were relying on the "belief that any layout can be signalled in compliance with BR's signalling principles" (para 320) and the fact that the HMRI Inquiry into the earlier Bellgrove collision had concluded (para 129) that single lead junctions "are acceptable in principle on safety grounds".

In the absence of an effective train protection system, this clearly proved a very flawed argument with the railway getting much busier during the late 1980s and early 90s and with management distracted by privatisation.

 

[Dr Hoo]

In the absence of an effective train protection system, this clearly proved a very flawed argument with the railway getting much busier during the late 1980s and early 90s and with management distracted by privatisation.

Whilst not disagreeing with your core point, serious collisions had been happening on 'unprotected' un-rationalised layouts for many years as well. Paisley Gilmour Street in 1979 for example. Track rationalisation (including singling) had been going on ever since the 1960s, especially after the Surplus Track Capacity [elimination] Grants were brought in as part of the Transport Act 1968. Both BR and the Inspectorate took a very long time to recognise the issues. It was nothing to do with privatisation (which hadn't been seriously proposed in 1991).

 

[MarkyT]

Whilst not disagreeing with your core point, serious collisions had been happening on 'unprotected' un-rationalised layouts for many years as well. Paisley Gilmour Street in 1979 for example. Track rationalisation (including singling) had been going on ever since the 1960s, especially after the Surplus Track Capacity [elimination] Grants were brought in as part of the Transport Act 1968. Both BR and the Inspectorate took a very long time to recognise the issues. It was nothing to do with privatisation (which hadn't been seriously proposed in 1991).

Fully agree at the time of Newton, but I'd argue the 'privatisation distraction' WAS in full force by the time Ladbroke Grove and Southall happened some years later, and to an extent in the years leading up to those incidents when the layouts were being developed and the decisions about adding ATP to the turbos in the case of Thames, and policies relating to protection system use and failure response on Great Western were being made. I don't think BR was as significantly behind in technical solutions as some might have claimed however. While DB and its predecessor for example had started implementing their Indusi system from the 1930s, incorporating an inductive train stop element, its extent was fairly patchy and only aimed at high traffic main lines initially. Some moderately trafficked single lines didn't get the equipment until much later, in some cases not until the 1990s, despite the obvious risk. The French KVB system, providing similar protections, wasn't rolled out until the 1990s either. Obviously SOME European railways were far ahead of the curve, with Sweden being nearly fully equipped with a full supervision ATP system in the 1970s.

 

[Falcon1200]

My memory is slightly different - that Motherwell drivers were relieved by Yoker at Blairhill, as soon as they had 'set foot' on the sacred eastern side of North Electrics (which only Yoker signed) but I may have that bit wrong.

Might well have been Shettleston or Blairhill, depending on timings.

 

[JamesT]

What is the definition of dynamic loop?

At a normal passing loop if trains are to cross there they are cautioned before entering the loop to stop the risk of runnjng theough onto the next single line section.
A dynamic loop has a proper overlap between the exit signals and the points and maybe even trap points, so trains can pass at line speed.
Is that about right???

My understanding is that a dynamic loop is long enough that both trains can keep running whilst passing each other. Whereas a non-dynamic one would have one of the trains stopped in the loop as the other passes it.

 

[steamybrian]

On the Appledore to Dungeness freight only line the passing loop at Lydd Town which was removed after the passenger service was withdrawn. Recently the loop was reinstated presume for loco run round purposes but other members of this forum may have further knowledge...

 

[snowball]

My understanding is that a dynamic loop is long enough that both trains can keep running whilst passing each other. Whereas a non-dynamic one would have one of the trains stopped in the loop as the other passes it.

That's my understanding too. The ability for trains to run non-stop on a dynamic loop may be somewhat dependent on them arriving at roughly the right time, but at least it isn't out of the question. For example on the Borders line the northern loop seems to be about 3km long and the other two about 5-6 km each. But the loop near Hairmyres is only about 500m long (with some to be taken off that for signalling overlaps), which I would have thought is far too short to qualify as dynamic.

 

[Dai Corner]

That's my understanding too. The ability for trains to run non-stop on a dynamic loop may be somewhat dependent on them arriving at roughly the right time, but at least it isn't out of the question. For example on the Borders line the northern loop seems to be about 3km long and the other two about 5-6 km each. But the loop near Hairmyres is only about 500m long (with some to be taken off that for signalling overlaps), which I would have thought is far too short to qualify as dynamic.

What's the difference between a dynamic loop and a stretch of double track?

 

[Taunton]

The Newton re-modelling was spread over several stages and weeks (I.e. not just weekends) so it definitely fell into the ‘weeks’ category but not something like a complete timetable period.

It is widely misunderstood that the ‘single line’ for the local services was to save a few yards of track. The main line realignment was so significant (to give the desired speed) that there was only enough space left within the BR boundary for one other line.

The subsequent ‘re-doubling’ required a lot of complex and expensive legal procedures to buy a strip of land under Scots property law that I won’t attempt to explain. For obvious reasons these were undertaken extremely discreetly.

Bit surprising again. It's only local authority landscaping of an adjacent road alongside the boundary there. But you have to ask why the main line was allowed to squish so far to the south, to get the last 5mph of linespeed, to the considerable inconvenience of multiple local services forced onto a single line. It's not that much of a curve there, but the connections are an issue. I believe the south side was once immediate post-war "prefabs" that were replaced by local authority housing, but not on the side nearest the railway.

Notably the formal accident report seems to make no mention of the desire for higher main line speed, only, again and again, to reduce BR maintenance costs. Perhaps that was felt to be a better corporate line to follow. Maybe it was the cheapest way to do higher speeds.

Did nobody think of detonator placers at the starting signal? The GWR stuck them in at various points with limited forward clearance.

 

[zwk500]

What's the difference between a dynamic loop and a stretch of double track?

There's only room for 1 train to pass another at a time. Although, in practice, there's very little.

 

[Railsigns]

What's the difference between a dynamic loop and a stretch of double track?

I would suggest that the geometry of the points where the single lines become double is a factor. The dynamic loop concept needs the switches and crossing to be sufficiently flat that trains aren't having to significantly reduce speed to negotiate them.

 

[snowball]

There's only room for 1 train to pass another at a time. Although, in practice, there's very little.

If that's the case then I would guess the ones on the Borders line are long enough to count as double track.

Another point is that you can add a dynamic or non-dynamic loop to a line that's already double track, to enable a faster train to overtake a slower one in the same direction. So then the question arises whether that is different from triple or quadruple track.

 

[Railsigns]

If that's the case then I would guess the ones on the Borders line are long enough to count as double track.

They may be long, but the absence of intermediate signals means they can only accommodate one train at a time on each line.

 

[zwk500]

If that's the case then I would guess the ones on the Borders line are long enough to count as double track.

Probably not, because you can't have 2 down trains cross 1 up train (or vice versa) without at least 1 train coming to a stand.

Another point is that you can add a dynamic or non-dynamic loop to a line that's already double track, to enable a faster train to overtake a slower one in the same direction. So then the question arises whether that is different from triple or quadruple track.

Dynamic loops permitting traffic to overtake in the same direction tend to be longer (by necessity) than those that permit passing of oncoming services. As such, they usually have multiple signalling berths and can accept a continuous flow of traffic. I don't think there's a hard and fast definition though - e.g. is the Down Slow from High Oaks Jn to Brinklow Jn a dynamic passing lane or just extension of the 4-track beyond Rugby? Challow Loops were (IIRC) designed as dynamic loops, but nowadays lots of things in them are timed to stop.

 

[swissrailpassion]

Dynamic means trains can run into both ends of the loop at the same time. Basically like a double section with suitable overlaps etc. Depending on arrangements, a following train can also be accepted.

 

[Railsigns]

Dynamic means trains can run into both ends of the loop at the same time.

The term for that is 'simultaneous arrival'. 'Dynamic loop' suggests something more.