Measuring using chains

[Rescars]

Today's BBC news includes a piece about rectification work following the landslip near Honiton tunnel. One of the photos shows a modern sign reading "Zero datum for tunnel inspection chainages". This makes me wonder, in the UK are the railways unique in continuing to use chains as a measure of distance? I have never come across them in any other connection, though IIRC one chain is the length of a cricket pitch.

 

[zwk500]

They're probably unique in continuing to use them, with everything else only needing to use fractions of a mile, or switching to metric. Although they probably weren't unique when they were built, the chain being a very common unit for surveyors and land. An Acre is 1 chain x 20 10 chains (1 furlong), for instance. (Edited in response to later posts pointing out the error!)
Some newer railways like HS1 and Crossrail core section (IIRC) have been built fully metric, and their 'chainages' are recorded in km:m on documentation. Existing railways and new lines connecting into the old network tend to be designed, built and documented in metric but then converted to Mi:Ch distance for operational publications so that staff don't have to deal with changing scales too often. Not sure when the change for engineering drawings from yards to meters took place.

 

[pdeaves]

For metric systems, distances are often still called 'chainages', even though they aren't measured in imperial units at all.

 

[Howardh]

For metric systems, distances are often still called 'chainages', even though they aren't measured in imperial units at all.

Film and video, even on a hard drive, is called "footage"! I know a chain's 22yrds through cricket, but not a clue on furlong, fathom, knot etc.

But interested to know if drivers under training are expected to user metric or imperial, or both? Eg - start to slow 2km from the station, and watch the signal 500 yards from the platform? Do they simply keep it to imperial to prevent confusion?

 

[Tio Terry]

Today's BBC news includes a piece about rectification work following the landslip near Honiton tunnel. One of the photos shows a modern sign reading "Zero datum for tunnel inspection chainages". This makes me wonder, in the UK are the railways unique in continuing to use chains as a measure of distance? I have never come across them in any other connection, though IIRC one chain is the length of a cricket pitch.

To be pedantic, a Cricket Pitch is one chain long, not the other way around!

I guess Horse Racing is about the only other thing that regularly uses miles and chains - and furlongs.

 

[87electric]

A furlong is 10 chains. Not 20, as listed above.

 

[mike57]

I have often wondered about the use of miles and chains in the railway world, but I would imagine that the pain and cost of changing everything to metric would just not be worth the trouble. I suppose the obvious question is how long will it last as miles and chains, as large sections of the network will not get any upgrade which would be the time to do it. So I assume the answer is not quite NEVER, but not in the foreseeable future.

 

[Howardh]

This has probably been explained on here so many times...but always baffled me why 4'8.5" was the standard gauge. Does my OCD no good at all. 4'6", 5', even 4'9" would have been fine!!! In hockey they changed form imperial to metric but kept the lines where they were, so the 25yd line is now 22.85m. Oh-come-on...!!!!!

 

[Dunfanaghy Rd]

Alfrey's bridge, between Mortimer and Southcote Jct. has a plate giving its mileage as 41m 80ch. Spot the error!
BTW the track chart gives the mileage as 41M 64ch.
Pat

 

[plugwash]

This has probably been explained on here so many times...but always baffled me why 4'8.5" was the standard gauge. Does my OCD no good at all. 4'6", 5', even 4'9" would have been fine!!!

I don't know for sure, but I suspect the reason is a change in how gauge was measured. Specifically I suspect that gauge was originally measured between rail centers, but as tolerances were tightened and heavier rails were introduced it made more sense to measure it beween the inside faces of the rails.

 

[Howardh]

I don't know for sure, but I suspect the reason is a change in how gauge was measured. Specifically I suspect that gauge was originally measured between rail centers, but as tolerances were tightened and heavier rails were introduced it made more sense to measure it beween the inside faces of the rails.

Possibly! Wider rails measued from centre = wheels not fitting!

 

[SargeNpton]

This has probably been explained on here so many times...but always baffled me why 4'8.5" was the standard gauge. Does my OCD no good at all. 4'6", 5', even 4'9" would have been fine!!! In hockey they changed form imperial to metric but kept the lines where they were, so the 25yd line is now 22.85m. Oh-come-on...!!!!!

There is an unsubstantiated story circulating, which starts off describing why the Space Shuttle booster rockets were that size. That story leads onto the 4 feet 8½ inch gauge on the railway.

As it goes on it says that that gauge was chosen as it was the one used for plateways in coal mines - which was the gauge for wheels on carts on the roads - which were that width because they fitted in to the ruts that most roads had (otherwise it would lead to axles breaking). That the ruts were that width in the first place was, allegedly, because that was the distance between wheels of a Roman chariot.

How true that all is remains to be seen.

 

[zwk500]

I don't know for sure, but I suspect the reason is a change in how gauge was measured. Specifically I suspect that gauge was originally measured between rail centers, but as tolerances were tightened and heavier rails were introduced it made more sense to measure it beween the inside faces of the rails.

The origins part of the wikipedia claims that 4'8" was a common regional gauge for wagonways in the North East, and has been used before by Stephenson, as it fitted the horse between the cart. There had been no 'standard' width of a chariot/cart, but betwen 4' and 5' was normal. Originally the S&D used 4'8" however it was relaxed by a further 1/2" to reduce wear on tight curves.

 

[LNW-GW Joint]

I have often wondered about the use of miles and chains in the railway world, but I would imagine that the pain and cost of changing everything to metric would just not be worth the trouble. I suppose the obvious question is how long will it last as miles and chains, as large sections of the network will not get any upgrade which would be the time to do it. So I assume the answer is not quite NEVER, but not in the foreseeable future.

Plenty of countries have made the conversion of their railways from imperial to metric - Canada, Australia, NZ, South Africa etc.
But names like "Twenty Mile Siding" remain.
London Underground is in metric (from a zero at Ongar!)
I suspect Crossrail is metric on the new TfL sections, remaining imperial on NR.

Network Rail measures locations* in miles and chains, but the components (track, OHLE etc) are engineered in metric.
You won't find any imperial measurements on HS1 or HS2, and Network Rail maintains the former under contract.

*except the Cambrian which was converted to metric when ETCS was introduced.

The Heathrow branch is also measured in metric km from Paddington, with a changeover from imperial at Heathrow Airport Jn (12m27c = 19.908km).
That's another line NR maintains under contract.
Manchester's Metrolink is measured in km from the central delta junction at Piccadilly Gardens, including the former heavy rail lines.
The Sheffield and Nexus metros are also in metric, but contrariwise, the Birmingham and Nottingham metros seem to be in imperial, as they co-locate with NR in places.

 

[snowball]

Numbering of overhead electrification supports on the WCML is based on miles from Euston as far as Weaver Junction, Manchester and Liverpool (done in the 1960s). North of Weaver Junction (done on the 1970s) it's based on kilometres from Euston. The ECML and more recent schemes are all kilometres.

 

[zwk500]

I have often wondered about the use of miles and chains in the railway world, but I would imagine that the pain and cost of changing everything to metric would just not be worth the trouble. I suppose the obvious question is how long will it last as miles and chains, as large sections of the network will not get any upgrade which would be the time to do it. So I assume the answer is not quite NEVER, but not in the foreseeable future.

Given it's seen as too much trouble to recount the miles when diversions or cutoffs are built, the chances of conversion to full metric are probably quite low as you suspect. However all new engineering drawings are now made out in meters and do have a 'chainage' marked, so in theory it would be possible to convert large parts of the network at some point.

 

[pdeaves]

I suspect Crossrail is metric on the new TfL sections, remaining imperial on NR.

That is correct.

 

[zwk500]

That is correct.

Is the East London Line extension metric between Silverwood Jn and Dalston Junction? That's also TfL Infrastructure but I have a sneaking suspicion because it was a conversion rather than new infrastructure it's still imperial.

 

[pdeaves]

Is the East London Line extension metric between Silverwood Jn and Dalston Junction? That's also TfL Infrastructure but I have a sneaking suspicion because it was a conversion rather than new infrastructure it's still imperial.

I believe so. Though, as someone stated above, engineering calculations are metric.

 

[Trestrol]

The origins part of the wikipedia claims that 4'8" was a common regional gauge for wagonways in the North East, and has been used before by Stephenson, as it fitted the horse between the cart. There had been no 'standard' width of a chariot/cart, but betwen 4' and 5' was normal. Originally the S&D used 4'8" however it was relaxed by a further 1/2" to reduce wear on tight curves.

The origins go back further to the Romans and Ancient Greeks. They had Rutway roads of 4'8 3/4" gauge.

 

[Rescars]

Many thanks for all your responses. More complexity than I never knew was there.

To be pedantic, a Cricket Pitch is one chain long, not the other way around!

I guess Horse Racing is about the only other thing that regularly uses miles and chains - and furlongs.

Nice one, Tio Terry. Despite the LNER's penchant for naming locomotives after racehorses, sadly I have never seen any indication that the ECML has ever been measured in furlongs!

 

[12LDA28C]

Film and video, even on a hard drive, is called "footage"! I know a chain's 22yrds through cricket, but not a clue on furlong, fathom, knot etc.

But interested to know if drivers under training are expected to user metric or imperial, or both? Eg - start to slow 2km from the station, and watch the signal 500 yards from the platform? Do they simply keep it to imperial to prevent confusion?

Drivers are trained using imperial measurements, the Sectional Appendix uses miles and chains and so do signallers, eg 'There's been a report of a bridge strike at Bungle Bridge, 30 miles and 46 chains, proceed at no more than 5mph over the bridge' etc.

Can't see that changing anytime soon, much like speed limits on roads and so on.

 

[zwk500]

The origins go back further to the Romans and Ancient Greeks. They had Rutway roads of 4'8 3/4" gauge.

As I mentioned, there was no 'standard' for ancient rutways. Some are 4'8 and a bit, but others are nearer 4' and some are nearly 5'.

Drivers are trained using imperial measurements, the Sectional Appendix uses miles and chains and so do signallers, eg 'There's been a report of a bridge strike at Bungle Bridge, 30 miles and 46 chains, proceed at no more than 5mph over the bridge' etc.

Can't see that changing anytime soon, much like speed limits on roads and so on.

Indeed, and this is probably the biggest sticking factor, as it embeds things into the network that can be very difficult to remove or change. For distances etc you'd need to republish every single operational document for the area concerned and sign everything twice, for a period of approximately 12 months while driver training takes place and then go through an equally costly process of removing the imperial measurements.

 

[Railsigns]

Network Rail measures locations* in miles and chains, but the components (track, OHLE etc) are engineered in metric.

*except the Cambrian which was converted to metric when ETCS was introduced.

I feel like I've mentioned this numerous times before, but locations on the Cambrian line are still measured in miles and chains, not metric.

 

[plugwash]

Someone mentioned that the Cambrian was metrificated as part of it's conversion to ETCS, do we know if the same has/will happen for other lines that are/will be converted?

Edit: as I was posting this, someone claimed that locations on the Cambrian were not metrificated........

 

[12LDA28C]

Of course one chain equals 4 rods (or poles) and a rod is equal to 25 links (therefore 100 links equals one chain)

 

[zwk500]

I feel like I've mentioned this numerous times before, but locations on the Cambrian line are still measured in miles and chains, not metric.

Someone mentioned that the Cambrian was metrificated as part of it's conversion to ETCS, do we know if the same has/will happen for other lines that are/will be converted?

Edit: as I was posting this, someone claimed that locations on the Cambrian were not metrificated........

The confusion probably stems from the fact that speeds *are* in metric, but distance is not:

 

[Rescars]

As I mentioned, there was no 'standard' for ancient rutways. Some are 4'8 and a bit, but others are nearer 4' and some are nearly 5'.


Indeed, and this is probably the biggest sticking factor, as it embeds things into the network that can be very difficult to remove or change. For distances etc you'd need to republish every single operational document for the area concerned and sign everything twice, for a period of approximately 12 months while driver training takes place and then go through an equally costly process of removing the imperial measurements.

With several thousands years of history here, I can see why you might end up with something like 4' 8 1/2", but if like Brunel you are designing something from scratch why choose 7' 0 1/4"?

As you so rightly point out, once things such as units of meaurement are embedded they are very difficult to change.

 

[LNW-GW Joint]

Is the East London Line extension metric between Silverwood Jn and Dalston Junction? That's also TfL Infrastructure but I have a sneaking suspicion because it was a conversion rather than new infrastructure it's still imperial.

If I'm reading Trackmaps correctly, ELL distances are in metric from a point west of Dalston Jn which is at 2m28c on the NLL and 0km500m on the ELL.
That puts Silwood Jn at around km 8 (my map has the extension under construction).
There's also a note that 10.04km on the ELL merges into 2m09c from CX after New Cross Gate.

 

[zwk500]

With several thousands years of history here, I can see why you might end up with something like 4' 8 1/2", but if like Brunel you are designing something from scratch why choose 7' 0 1/4"?

Brunel always liked to think big... The normal explanation I have heard is that it's a combination of wanting stability at high speeds and giving room for inside cylinders. @Taunton will probably have a better explanation than me.

If I'm reading Trackmaps correctly, ELL distances are in metric from a point west of Dalston Jn which is at 2m28c on the NLL and 0km500m on the ELL.
That puts Silwood Jn at around km 8 (my map has the extension under construction).
There's also a note that 10.04km on the ELL merges into 2m09c from CX after New Cross Gate.

Somebody with access to NESA will need to confirm. The PDFs available on NR's website have removed the ELL from the Anglia Regional booklet but not yet added the table A into the Kent & Sussex Regional booklet, AFAICT.