Understanding Loading Gauge

Greg Wetzel · 21 Aug 2019

Hello,

I'm having trouble understanding what loading gauge means and how it works. I've read a couple of websites on it and looked at a railway book of mine that discusses it as clearances, and it's clear to me that I need it sadly dumbed down to the simplest explanation.

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plugwash · 21 Aug 2019

In it's most naive form "loading gauge" defines the maximum width and height of vehicles that can pass down a railway line safely. The builer of the railway line will need to take those maximum sizes, add a safety margin and make sure they don't

In reality things get more complex than that, for a number of reasons including

* The allowed shape may not be rectangular, the top may be curved and widths close to track level may be narrower than at load height.
* Railway lines have curves. When a vehicle goes round a curve the center of the vehicle will overhang the inside of the curve and the ends will overhang the outside. This must be allowed for, for example by requiring that the width requirements must still be complied with when the vehicle is going round a standardised radius of curve.
* Railway vehicles have suspension, this allows some movement of the vehicle away from it's neutral position as it goes along the line. The faster the vehicle moves the greater the offsets in the suspension.
* The railways have a long and messy history, there are a whole pile of standards and on top of that there are cases where part of the railway is technically non-compilant with a particular standard loading gauge but in practice ok for most stock designed to that gauge.

DarloRich · 21 Aug 2019

Greg Wetzel said:
Hello,

I'm having trouble understanding what loading gauge means and how it works. I've read a couple of websites on it and looked at a railway book of mine that discusses it as clearances, and it's clear to me that I need it sadly dumbed down to the simplest explanation.

lets try this: The loading gauge is the space available for a train to run down the track without crashing into the scenery.

( OBVIOUSLY that is very simplified and while not exactly accurate will do for this discussion)

themiller · 21 Aug 2019

DarloRich said:
lets try this: The loading gauge is the space available for a train to run down the track without crashing into the scenery.

( OBVIOUSLY that is very simplified and while not exactly accurate will do for this discussion)

I think what you described is the structure gauge.

EvoIV · 21 Aug 2019

There are two things which are sometimes conflated, route availability and loading gauge.

Route availability is effectively the heaviest axle loads that can run on a route and is written as RA followed by a number, increasing in weight, e.g. RA7. Each rail vehicle has such a number and the sectional appendix lists the routes and the maximum route availability number allowed. Even then, it's possible on some routes to run with a higher route availability, so long as a RT3973HAW form is produced and given to the driver. This will list the exact route to be observed and any extra restrictions to be obeyed such as reduced speeds over certain structures.

The loading gauge is simply the biggest width and height of any rail vehicle allowed to run over a route and is written as W followed by a number for freight and C followed by a number for passenger stock. Again higher is wider and/or taller. The loading gauge is the structure gauge of a route (the size of the most restrictive bridge/tunnel/platform etc.) plus a safety margin. Common loading gauges for freight are W8, which essentially all container freight routes allow - standard height containers on standard height wagons or high cube containers on low platform wagons - and W10, high cube containers on standard height wagons. Many container freight routes are now W10 cleared. It gets more messy when swapbodies are involved. As with route availability a RT3973 form is essential, this one is called a RT3973CON and must be produced for each train giving the allowed routes for the particular loading gauge of train and any restrictions or blocked parts of the route, e.g. certain platforms. Many yards have overheight detectors which are used as part of the departure examination. And yes they are occasionally activated!

I believe the goal for most new structures is W12 clearance which is virtually any single stacked intermodal box and wagon combination possible.

DarloRich · 21 Aug 2019

themiller said:
I think what you described is the structure gauge.

of course it is! Brain fart. No Coffee.

furnessvale · 21 Aug 2019

DarloRich said:
of course it is! Brain fart. No Coffee.

No, I think you were correct first time round.

The "scenery" (as you quaintly call it) must conform to the structure gauge. The train must conform to the loading gauge. As long as the structure gauge is bigger than the loading gauge, all is well!

JKF · 21 Aug 2019

What famous/infamous episodes have there been of out-of-gauge stock being involved in mishaps? I have a vague recollection of something being sent down the Burry Port line in South Wales (very low clearance due to line being created from an old canal) and not ending well.

pdeaves · 21 Aug 2019

JKF said:
What famous/infamous episodes have there been of out-of-gauge stock being involved in mishaps? I have a vague recollection of something being sent down the Burry Port line in South Wales (very low clearance due to line being created from an old canal) and not ending well.

Yes, ended up with an italic 08.

There have been various instances of bits of steam locomotive striking bridges (dome/safety valve?) and platforms (cylinder casing).

GB · 21 Aug 2019

JKF said:
What famous/infamous episodes have there been of out-of-gauge stock being involved in mishaps? I have a vague recollection of something being sent down the Burry Port line in South Wales (very low clearance due to line being created from an old canal) and not ending well.

Over height container train damaged Basingstoke's station canopy in 2008.

EvoIV · 21 Aug 2019

The platform canopy was damaged at Basingstoke in 2005-ish. Don't know first hand of any others though I have a vague memory of seeing a picture of some wagons wedged into a bridge in the West country somewhere.

EvoIV · 21 Aug 2019

GB said:
Over height container train damaged Basingstoke's station canopy in 2008.

Ah yes that's the one I was thinking of.

3973EXL · 21 Aug 2019

Greg Wetzel said:
Hello,

I'm having trouble understanding what loading gauge means and how it works. I've read a couple of websites on it and looked at a railway book of mine that discusses it as clearances, and it's clear to me that I need it sadly dumbed down to the simplest explanation.

Lets look at this from the Operations side of Freight loading (short basic versions).

Don't let all the different Gauges confuse you. Basically, unless you are talking about Containers (ISO/Swapbodies) there is only one gauge.

W6A gives you the maximum width at heights above rail level that can be loaded on a wagon.
This is dependent on the wheelbase/bogie centres of the wagon being loaded, so is split into different ranges.
(The further apart the WB/BC, the more centre throw there is on curves, so width has to be decreased).
This gauge also covers loads longer than the wagon using under runners. The length of the load is limited because it is subject to end throw on curves and width decreases as length increases.

This gauge is rather basic in some ways but is for everyday use by competent operations staff. Only one maximum width is given for the whole length of wagon even though centre throw differs along the length. This can be calculated, and the wagon designed to take advantage of this. So using W6A a wagon may appear to be out of gauge.

It may be possible to load in excess of W6A, Exceptional Load. This requires authority from Network Rail with a RT3973EXL. Written authority giving maximum dimensions and any conditions of travel. Details of the load, wagon and route are submitted to the NR Gauging Engineer for comparison with actual structures. Speed limits may be imposed at certain locations or even not passing other trains at certain locations.
Simple way to look at it, between actual wagon/load, there is a safety envelope between structures and other trains so there is no contact.

There are very few areas of NR not cleared for W6A, Thameslink core being one.

W7 - W12 are only for load units (ISO containers and Swapbodies).
This has developed over the years as first the standard height has increased, then the width with swapbodies.
These gauges are not higher than W6A, but where the top is a curve, what are sometimes referred to as "ears" have been cleared to allow bigger boxes.
Low floor wagons have also been used to load bigger boxes, but operationally, gauge enhancement where possible to W10/12 is best.

broadgage · 21 Aug 2019

I recall an incident in which a steamer was over height for a bridge over the line just outside Paddington station. As a result a fitting atop the boiler struck the bridge.
The same loco, or another one of identical dimensions had previously passed under the same bridge, but the track had been slightly raised in the interim.

Under exceptional conditions, loads that are out of gauge have been moved by rail. I have seen an old film about the movement of a large transformer by rail. The load was placed on a suitable wagon and was moved from side to side upon this wagon in order to pass locations where the clearance was insufficient on one side.
One a smaller scale, I have assisted in the movement of a modular building by train on a heritage line. Achieved also by moving the portable building on the wagon, at a couple of locations.

krus_aragon · 21 Aug 2019

JKF said:
What famous/infamous episodes have there been of out-of-gauge stock being involved in mishaps? I have a vague recollection of something being sent down the Burry Port line in South Wales (very low clearance due to line being created from an old canal) and not ending well.

pdeaves said:
Yes, ended up with an italic 08.

Here it is:

From http://www.combsmr.co.uk/g01.html

(It should only have been operated with a sub-fleet of 08s that had their cabs lowered.)

furnessvale · 21 Aug 2019

3973EXL said:
<SNIP>

W7 - W12 are only for load units (ISO containers and Swapbodies).
This has developed over the years as first the standard height has increased, then the width with swapbodies.
These gauges are not higher than W6A, but where the top is a curve, what are sometimes referred to as "ears" have been cleared to allow bigger boxes.
Low floor wagons have also been used to load bigger boxes, but operationally, gauge enhancement where possible to W10/12 is best.

Given how much railway is now cleared for various container gauges it is high time that conventional wagons be allowed to use this additional space.

Such wagons could be restricted to set routes in exactly the same way that overheight containers are also restricted.

3973EXL · 21 Aug 2019

furnessvale said:
Given how much railway is now cleared for various container gauges it is high time that conventional wagons be allowed to use this additional space.

Such wagons could be restricted to set routes in exactly the same way that overheight containers are also restricted.

What traffic is there that could take advantage of this?
Cleared routes are based on container flows.
Introduces complications.
Already is in a controlled manner through the exceptional load procedure.

ac6000cw · 21 Aug 2019

I suspect the term 'loading gauge' derives from the (old) days when most railway goods yards etc. had a physical 'loading gauge' hanging over one of the yard tracks. It was used to check that freight loaded onto open wagons wasn't too high or wide.

An example of one from the Great Western Society, Bristol Branch, here - http://www.gwsbristol.org/hothbuild.html - "This loading gauge is from Frome Goods Yard (Tar Depot) - It is of the type with lifting ends which can be lowered to gauge for the narrower clearances available to wagons travelling on the Southern Railway" (the GWR had a more generous structure gauge on its mainlines than other railways due to its broad-gauge history).

3973EXL said:
What traffic is there that could take advantage o this?
Cleared routes are based on container flows.
Introduces complications.

I agree - now that nearly all 'general merchandise' rail freight travels in containers or swapbodies, and the rest is mostly is bulk commodities which tend to travel in wagons designed for those commodities, the gauge clearance issues are already dealt with.

800002 · 21 Aug 2019

There was an engineers train a couple years ago, going through Newcastle, which rounded off some of the wagon corners on the cope stones as it traversed the platform.
Can't recall if it was down to mis-routing / planning error or recent track alignment / tamping.

Journeyman · 21 Aug 2019

pdeaves said:
Yes, ended up with an italic 08.

There have been various instances of bits of steam locomotive striking bridges (dome/safety valve?) and platforms (cylinder casing).

This regularly occurred on the Great Central at one infamous location, disproving the widely-held belief that it was built to "continental" loading gauge.

furnessvale · 21 Aug 2019

3973EXL said:
What traffic is there that could take advantage of this?
Cleared routes are based on container flows.
Introduces complications.
Already is in a controlled manner through the exceptional load procedure.

If the question isn't asked we will never know. For a start, biomass is incapable of loading existing wagon designs to a full 25ton axle load.

3973EXL · 21 Aug 2019

furnessvale said:
If the question isn't asked we will never know. For a start, biomass is incapable of loading existing wagon designs to a full 25ton axle load.

It also has to be loaded in covered wagons.

furnessvale · 21 Aug 2019

3973EXL said:
It also has to be loaded in covered wagons.

Yes? Those covered wagons could be built to a larger gauge IF a route was available.

3973EXL · 21 Aug 2019

furnessvale said:
Yes? Those covered wagons could be built to a larger gauge IF a route was available.

How much of the routes from the ports to Drax is W10/12. Build them to the largest gauge, they can't go anywhere else.
Drax had the wagons built to take maximum advantage of the go anywhere gauge.

furnessvale · 21 Aug 2019

3973EXL said:
How much of the routes from the ports to Drax is W10/12. Build them to the largest gauge, they can't go anywhere else.
Drax had the wagons built to take maximum advantage of the go anywhere gauge.

You are now dissecting one possible example. I am simply trying to establish a principle that enlarged gauges should not be exclusively available to shipping containers. If the right opportunity arises for dedicated conventional wagons on a particular route, it should be allowed.

GB · 21 Aug 2019

Gauge enhancements should be done where it makes sense and financially viable. How much more product could you actually load with a W10/12 gauge enhancement and what affect is there if this is not done?...could you not just add extra wagons to services etc? It is important that gauge enhancements take place for containers as without these schemes you would severely impact on the shipping industry and rail intermodal industry, create more road congestion and subsequently more environmental problems.

Also, with bulk traffic, you are more likely to overload the train by weight than by volume.

3973EXL · 21 Aug 2019

furnessvale said:
You are now dissecting one possible example. I am simply trying to establish a principle that enlarged gauges should not be exclusively available to shipping containers. If the right opportunity arises for dedicated conventional wagons on a particular route, it should be allowed.

I've already said there is a procedure in place to deal with loads on excess of W6A and the reasons for not implementing your suggestion.

furnessvale · 21 Aug 2019

GB said:
Gauge enhancements should be done where it makes sense and financially viable. How much more product could you actually load with a W10/12 gauge enhancement and what affect is there if this is not done?...could you not just add extra wagons to services etc? It is important that gauge enhancements take place for containers as without these schemes you would severely impact on the shipping industry and rail intermodal industry, create more road congestion and subsequently more environmental problems.

Also, with bulk traffic, you are more likely to overload the train by weight than by volume.

ALL fully agreed, but none of which answers my basic question. If an enlarged gauge already exists, thanks to containers, can I build a fleet of restricted access conventional wagons to use it if I have suitable traffic?

I am thinking about perhaps palleted lightweight goods. As things stand, I could put a 50ft long curtainside container on a flat wagon and use it as a conventional wagon on a cleared route. Maybe I could get better profitability if I could use a purpose made conventional wagon but can I do so?

edwin_m · 21 Aug 2019

furnessvale said:
ALL fully agreed, but none of which answers my basic question. If an enlarged gauge already exists, thanks to containers, can I build a fleet of restricted access conventional wagons to use it if I have suitable traffic?

I am thinking about perhaps palleted lightweight goods. As things stand, I could put a 50ft long curtainside container on a flat wagon and use it as a conventional wagon on a cleared route. Maybe I could get better profitability if I could use a purpose made conventional wagon but can I do so?

There's nothing in the rules to prevent this. Just that wagon owners prefer a go-anywhere design that can be used for the widest variety of flows regardless of gauge. Incidentally it works the other way round too - the Tesco containers are to a smaller profile than would be allowed on the WCML, so they can be diverted onto other routes.

3973EXL · 21 Aug 2019

At the end of the day it would be up to Network Rail.

Unless you have a product made at A, has a route cleared to B, where the product is used, with enough tonnage for a long enough timescale, how do the finances stack up against the swapbody? If the traffic ends, what use are the wagons to anybody else?

Understanding Loading Gauge

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