Does Network Rail have an over-engineering problem?

[BRX]

Every time I see this gantry at Tulse Hill I wonder: is so much steel really necessary to support a couple of colour light signals (plus a human maintaining them)?



(Image is of a signal gantry with very substantial steelwork)

There are lots of other examples, including most station footbridges built in the last 10-20 years.

Am I being unfair - is there actually good justification for building everything in a way that looks like it has been designed to withstand nuclear attack?

 

[Coleridge]

I've noticed the same with regard to the electrification of the Welsh valleys: the masts supporting the wires are overbearing and very unattractive. Perhaps unsightly structures are cheaper to erect than elegant ones.

And don't get me started on the ugly footbridges that are appearing across the network...

 

[Notabene]

I think they must have shares in steel lol.

I find the aesthetics of it all rather depressing. What happened to elegance in design and form? I see recent high speed electrification in Italy and it is far less obtrusive.

Signalling in the 90s went down the same route, producing hideously ugly signal posts, cages and brackets.Function over form.
Things have, at last, improved with lightweight signals by Dorman and others.

 

[BRX]

I think they must have shares in steel lol

Concrete too. These monsters need big foundations.

 

[Geeves]

I understand that the design on the WCML that tried to address the apparent over engineering was not a success. The signal heads could be lowered to the ground to avoid working at height. I don't think they were ever installed anywhere else but happy to be corrected.

Any at height signals need a walkway that is strong enough to carry the weight of the equipment, the staff up there and what ever heavy tools you need so I think there's much choice!

 

[The exile]

Any at height signals need a walkway that is strong enough to carry the weight of the equipment, the staff up there and what ever heavy tools you need so I think there's much choice!

How much work gets done on signal heads (or anything else “up there”) while trains are still running on the line they control?

 

[Purple Train]

Better than having an under-engineering problem a la Bouch (who I have much sympathy for, for the record). As a fully paid-up member of the Make All New Railway Station Buildings High Victorian Gothic Whatever The Cost Society, I do take the point about aesthetics, but ultimately I'd far rather have confidence and assurance that something's been essentially designed to be bombproof as opposed to the worry of the infrastructure not being sound, and/or the tedium of e.g. cheap overhead wires falling over at the slightest breath of wind. Much as I love a lattice footbridge.

 

[SynthD]

There’s two questions. Does the signal need to be elevated, and does an elevated signal need a platform multiple people can stand on?

That’s a two year old gantry. Did that Victoria lines project install non-overhead signals (including the left turn) that could have been used here?

 

[GRALISTAIR]

Most (all) engineers I know prefer to err on the side of caution aka over-engineer. My brother specified 9x2 joists on our house extension. When Preston Council came by to double check and sign off on the installation, he said “ well I am not even going to bother double checking the structural calcs for those!”

 

[Coleridge]

Better than having an under-engineering problem a la Bouch (who I have much sympathy for, for the record). As a fully paid-up member of the Make All New Railway Station Buildings High Victorian Gothic Whatever The Cost Society, I do take the point about aesthetics, but ultimately I'd far rather have confidence and assurance that something's been essentially designed to be bombproof as opposed to the worry of the infrastructure not being sound, and/or the tedium of e.g. cheap overhead wires falling over at the slightest breath of wind. Much as I love a lattice footbridge.

I think there might be a middle ground between "bombproof" and "falling over at the slightest breath of wind". Other countries seem to be able to build gantries and masts that blend into the scenery and don't fall over.

 

[GRALISTAIR]

I think there might be a middle ground between "bombproof" and "falling over at the slightest breath of wind". Other countries seem to be able to build gantries and masts that blend into the scenery and don't fall over.

Very true - where that middle ground is can be open to debate. In fairness, our climate is different and that has to be taken into consideration.

 

[The exile]

Very true - where that middle ground is can be open to debate. In fairness, our climate is different and that has to be taken into consideration.

Though with a very few exceptions (Dawlish Sea Wall being one), I doubt there are many locations on our network exposed to weather more extreme than somewhere not that far away on a Northern European railway network.

 

[Trainman40083]

All very interesting. OHLE. With the over engineered structures such as on Great Western. Are there less incidents of wires coming down? Signal structures. Some will caused by signal sighting. They will be manufactured to carry the weight of engineers. Of course you don't want them falling down a ladder so you have a cage. You don't what the cross member to sag coming into conflict with a train passing underneath (I can't recall where, but one did). With LED signal heads now the norm, there is less need to climb the structure to replace such as SL35 light bulbs... Forgotten how many hours they lasted (and that depended upon voltage, which should have been 110V). Of course, one benefit of less signal poles, is less risk to the engineer walking to it /working on it. Many signal poles are how hinged too, to bring it to ground, so no-one has to go up a ladder. Wonder if they ever did that with level crossing lights. There was certainly a plan to. I've forgotten what wind force the structures had to withstand. Probably tornado ️

 

[GRALISTAIR]

S

Though with a very few exceptions (Dawlish Sea Wall being one), I doubt there are many locations on our network exposed to weather more extreme than somewhere not that far away on a Northern European railway network.

do they get the extreme swings we get though?

 

[BRX]

Here's a slightly earlier (I think) vintage of gantry which appears to be doing much the same job as the one in my OP.

So what's led to the massively heftier design? It's not a subtle difference. The horizontal cantilevering member in the Tulse Hill one must use something like 5-10 times the amount of steel compared to this - I don't think that's an exaggeration. And the diagonal bit that braces it against the stalk is orders of magnitiude bigger.



Have there been instances where a design like the one pictured here fail in some way?

Is it to do with maintenance? Is the idea that 95% of the Tulse Hill gantry can rust away and it'll stay standing?

 

[ikari2006]

On the photo, it's quite a long cantilever which is probably why the sections are so bulky. Plus Network Rail standards are onerous given the need for 120 year design life with (ahem) minimal maintenance. Overly cautious designer perhaps? I recall talk back in early 1990s to have speed limits/signals put into cabs using lineside transmitters (this was pre-wifi/GPS) but for some reason they wanted to keep a visible speed limit sign which kind of defeated the point. Perhaps the question could be: are external physical systems necessary when we could put it all in the cab and/or automate it? Removes the maintenance liability and initial infrastructure cost; existing systems elsewhere in the world (thinking very high speed rail) probably already do this. (Note I am not advocating for one or the other.)

Addition, what are the ages of both? Presumably chunky is elastic/permissible stress design (older) and the slender is Plastic Ultimate Limit state? i.e. designed to different codes at different times.

 

[BRX]

Most (all) engineers I know prefer to err on the side of caution aka over-engineer.

All structural engineers err on the side of caution in the sense that there are safety factors built in. But good engineers can produce structures that are very efficient in the amount of material they use whilst staying well within those margins.

I'm interested in what leads to the design culture we see at Network Rail. It's probably not "bad engineers". It might be engineers caught within specification standards that have gotten out of hand. It may be an approach to risk at higher levels.

 

[CharlieSpotted]

Speculating, but I wonder if there's some local reason for the Tulse Hill example being such a big boy? Something to do with unstable ground? Mineshafts? Nothing more than an idle thought.

 

[BRX]

Speculating, but I wonder if there's some local reason for the Tulse Hill example being such a big boy? Something to do with unstable ground? Mineshafts? Nothing more than an idle thought.

It's perched on a slope right next to a bridge abutment so I can see why the foundations might be difficult/substantial. That doesn't explain the above ground bit though.

 

[John Webb]

Speculating, but I wonder if there's some local reason for the Tulse Hill example being such a big boy? Something to do with unstable ground? Mineshafts? Nothing more than an idle thought.

The line is on an embankment and about to go across a road on an overbridge. While I don't think there's ever been mining there, there may be other geological circumstances coming into play. But it certainly isn't the most elegant....

 

[High Dyke]

How much work gets done on signal heads (or anything else “up there”) while trains are still running on the line they control?

Interesting question. To some extent quite a bit, as the staff won't need a line blockage during the work, that a ground fixed signal might.

As an aside I've seen footage of staff carrying out overhead line work whilst trains still run underneath. Admittedly it was in Switzerland, which may have a different work ethos.

 

[3RDGEN]

Most (all) engineers I know prefer to err on the side of caution aka over-engineer. My brother specified 9x2 joists on our house extension. When Preston Council came by to double check and sign off on the installation, he said “ well I am not even going to bother double checking the structural calcs for those!”

The ones who did the ECML electrification/remodeling certainly didn't over-engineer because they had a budget to stick to.

Am I being unfair -

No, your correct.

 

[TSG]

I understand that the design on the WCML that tried to address the apparent over engineering was not a success. The signal heads could be lowered to the ground to avoid working at height. I don't think they were ever installed anywhere else but happy to be corrected.

Any at height signals need a walkway that is strong enough to carry the weight of the equipment, the staff up there and what ever heavy tools you need so I think there's much choice!

The fold down signals are still being installed probably everywhere they can be, as you say to avoid working at height. They can't be used everywhere though. For starters you need physical space to fold them down. Also, the folding signals can only put a signal to the side of the line, constrained by gauging, at particular heights. In many places signal sighting is simple and that works fine. On a four track railway through a city these things make fold downs much more challenging.

In this case, putting it on a bridge hasn't helped. Having a longer arm on a taller upright obviously needs a stronger structure at the root. The life requirement would need it to be more substantial. Its also possible that, coming back to the requirements of the Working at Height regulations, the additional loading when anchoring an arrested fall has been considered.

 

[Trainman40083]

The ones who did the ECML electrification/remodeling certainly didn't over-engineer because they had a budget to stick to.

No, your correct.

Ah the ECML electrification project. You can only do the work if it can be done for £*** million.. So economies were made on the infrastructure and rolling stock. I wonder how much money has been spent trying to put it right? How many times have the wires come down, certainly south of Peterborough?

 

[quantinghome]

Not just a Network Rail problem. There are examples of overengineering on all kinds of infrastructure projects, and it does appear to be getting worse as an issue.

 

[RUK]

It’s better that than what happened at Wickford, where the derailed train hitting the electrification mast bent the mast and meant that the mast needed to be replaced.

 

[Trainman40083]

It’s better that than what happened at Wickford, where the derailed train hitting the electrification mast bent the mast and meant that the mast needed to be replaced.

With ongoing delays to trains, and of course the OHLE structure may not have a readily available replacement.

 

[hwl]

Every time I see this gantry at Tulse Hill I wonder: is so much steel really necessary to support a couple of colour light signals (plus a human maintaining them)?

View attachment 212793

(Image is of a signal gantry with very substantial steelwork)

There are lots of other examples, including most station footbridges built in the last 10-20 years.

Am I being unfair - is there actually good justification for building everything in a way that looks like it has been designed to withstand nuclear attack?

Speculating, but I wonder if there's some local reason for the Tulse Hill example being such a big boy? Something to do with unstable ground? Mineshafts? Nothing more than an idle thought.

The line is on an embankment and about to go across a road on an overbridge. While I don't think there's ever been mining there, there may be other geological circumstances coming into play. But it certainly isn't the most elegant....

The fold down signals are still being installed probably everywhere they can be, as you say to avoid working at height. They can't be used everywhere though. For starters you need physical space to fold them down. Also, the folding signals can only put a signal to the side of the line, constrained by gauging, at particular heights. In many places signal sighting is simple and that works fine. On a four track railway through a city these things make fold downs much more challenging.

In this case, putting it on a bridge hasn't helped. Having a longer arm on a taller upright obviously needs a stronger structure at the root. The life requirement would need it to be more substantial. Its also possible that, coming back to the requirements of the Working at Height regulations, the additional loading when anchoring an arrested fall has been considered.

The signal gantry is on an "embankment" adjacent to the south circular and the ground conditions are very poor with minimal flexibility in locating the singal for signal spacing reasons. The foundations are two huge steel piles (the largest diameter used for problem OHLE structures).The local ground level is about 4' below the track level and the ground the piles are outside the wing wall.
The is also a singal on the other side of the gantry along with another speed sign (mounted between the gusset and the hidden signal). There is no space here for any ground mounted signals let alone fold down signals and the speed signage.

The bridge deck has seen better days so keeping the signals clear of anything to do the bridge deck will make replacement easier.

The railings are bit squiffy (especially 2nd panel to the left of the brick) because that is just above the point where all the lorries hit (it used to be a regular member of the top 10).

PS this structure was installed 2.5 to 3 years ago

 

[Nicholas Lewis]

I think there might be a middle ground between "bombproof" and "falling over at the slightest breath of wind". Other countries seem to be able to build gantries and masts that blend into the scenery and don't fall over.

Look at the gantries (below is BR SR example probably late 60s) that were installed under the original 1980s Victoria Resignalling Scheme and they are at least half the section size on steelwork. They also have to support a four aspect filament head which weighs more than a two aperture LED head. To my knowledge none of them ever fell down or were restricted on access for maintenance staff.

What I do acknowledge is that working at height regulations have been tightened up and that requires ladders with hoops. I suspect average weight of maintenance staff has probably been increased as well. However, none of that should result in a structure of this side although even straight signal posts have grown in size. The other thing thats changed today is British Rail used to have the design staff but its all outsourced now and the designers need to protect themselves so its over engineered and no NR responsible engineer is likely to challenge it.

And we wonder why building anything on the railway costs so much.

 

[BRX]

It’s better that than what happened at Wickford, where the derailed train hitting the electrification mast bent the mast and meant that the mast needed to be replaced.

This doesn't make sense - you surely have to balance the cost of building 1000s of masts strong enough to withstand the impact of a derailed train, with the cost of replacing one slimmer mast, in the very rare event of a train derailing.

Additionally, it is surely much preferable that an electrification mast distorts on impact, than the train body.