Re–calulating mileages after closure/abandonment of original routes?

[Chrius56000]

Is there any reason why mileages/mileposts along a route where the former "zero point" was on a route now closed and abandoned aren't re–measured or replotted?

I quote as one example the Talerddig Loop on the Cambrian Lines, which the Accident Report recently published by RAIB refers to as "being measured from a zero point near Whitchurch on the closed Oswestry route" – I would have thought that the Cambrian Line could have a zero datum redesignated as "Sutton Bridge Junction".

. . .Incidentally when a route is closed and subsequently lifted, are the old/former mileposts normally removed at the time of closure?

== Doublepost prevention - post automatically merged: 22 Jun 2026 ==

I can understand it not being done when B.R.'s Sectional Appendices had to be typeset and written/drawn by hand, but in these days the Sectional Appendices are produced (I believe!) in Adobe Illustrator and wouldn't be a vast amount of work to amend as the old printed B.R. Books were!

Am I being over–simplistic here?

 

[150219]

Is there any reason why mileages/mileposts along a route where the former "zero point" was on a route now closed and abandoned aren't re–measured or replotted?

I quote as one example the Talerddig Loop on the Cambrian Lines, which the Accident Report recently published by RAIB refers to as "being measured from a zero point near Whitchurch on the closed Oswestry route" – I would have thought that the Cambrian Line could have a zero datum redesignated as "Sutton Bridge Junction".

. . .Incidentally when a route is closed and subsequently lifted, are the old/former mileposts normally removed at the time of closure?

== Doublepost prevention - post automatically merged: 22 Jun 2026 ==

I can understand it not being done when B.R.'s Sectional Appendices had to be typeset and written/drawn by hand, but in these days the Sectional Appendices are produced (I believe!) in Adobe Illustrator and wouldn't be a vast amount of work to amend as the old printed B.R. Books were!

Am I being over–simplistic here?

That's a lot of work for little benefit. If station 'a' has always been at 'n' mileage, then think of all the paperwork that needs changing. Cutting routes into pieces over different years, such as the North Devon line, would've meant changing the mileages more than twice.

It's not just the Sectional Appendix that records the mileages, there are signalling scheme plans, asset registers, gradient profiles, etc. etc.

 

[dosxuk]

Mileage's are primarily for the identification of structures, assets and locations. Changing those identifications because other lines have closed makes little sense.

The starting point for mileages is pretty arbitrary anyway, and there's nothing which says they need to start at zero. In hindsight, it might have been better to start at random numbers anyway so people don't read more into their meaning than needed anyway.

 

[The exile]

Is there any reason why mileages/mileposts along a route where the former "zero point" was on a route now closed and abandoned aren't re–measured or replotted?

I quote as one example the Talerddig Loop on the Cambrian Lines, which the Accident Report recently published by RAIB refers to as "being measured from a zero point near Whitchurch on the closed Oswestry route" – I would have thought that the Cambrian Line could have a zero datum redesignated as "Sutton Bridge Junction".

. . .Incidentally when a route is closed and subsequently lifted, are the old/former mileposts normally removed at the time of closure?

== Doublepost prevention - post automatically merged: 22 Jun 2026 ==

I can understand it not being done when B.R.'s Sectional Appendices had to be typeset and written/drawn by hand, but in these days the Sectional Appendices are produced (I believe!) in Adobe Illustrator and wouldn't be a vast amount of work to amend as the old printed B.R. Books were!

Am I being over–simplistic here?

At least one issue would be where to draw the line. The “lawn” at Paddington was extended some years back meaning that the GW “0” is now several yards behind the buffer stops. Theoretically virtually every milepost on ex-GWR metals therefore “needs” re-siting; but is it really worth it?
All London Underground Km measurements start from 0 at a station no longer served by them. Does it matter?

 

[zwk500]

Is there any reason why mileages/mileposts along a route where the former "zero point" was on a route now closed and abandoned aren't re–measured or replotted?

A significant one is the cost. Of the survey itself, and then of updating every document to reflect the new mileages.

 

[JKF]

Also consider when historical information needs to be consulted, e.g. for excavation works - if there is a record of a culvert on an old plan at 78m12ch then it might be hard to locate if everything has been remeasured at some point since. This sort of thing could be safety critical.

 

[Beebman]

Distances on the GWML in Cornwall are measured from Paddington via Millbay, the original GWR terminus in Plymouth, so they're about a mile more than they should be. In fact mileages are via Bristol TM and they weren't recalculated when the Berks and Hants line opened (similarly mileages in South Wales are via Gloucester and weren't recalculated when the Severn Tunnel opened).

(A quick example in France - the extensive network of SNCF lines in the Ardennes are generally measured from a zero point at Soissons via a place called Bazoches - but the line between Soissons and Bazoches closed back in 1938.)

 

[zwk500]

Worth pointing out some lines were resurveyed, for example the Midland Railway had a big exercise that rearranged as much as possible to have the Zero point at St Pancras (which is why it's Down from Derby to Bristol).

Nowadays with computer systems handling Changes of Mileage pretty much automatically, there's little reason to remile and cause every bridge to have it's plate changed. There's isolated edge cases (Like the London-Brighton Line) where the history of it's construction means the datum changes regularly but with only small variations, but people tend to not need to calculate distances around the network from the mileages as much, so as long as the computer can calculate the difference, it doesn't matter.

 

[OVS Flatbottom]

The Belfast to Bangor line was re-mileposted with the zero at Dublin Connolly (instead of Belfast Queen's Quay) when the Belfast Central Railway reopened in the 1970s (I've always wondered whether there was any political controversy around that, given the characteristics of North Down...). Presumably the justification was that it would be operating as an extension of the Portadown-Lisburn-Belfast corridor, so it was convenient for it to have common mileages.

 

[Sir Felix Pole]

Distances on the GWML in Cornwall are measured from Paddington via Millbay, the original GWR terminus in Plymouth, so they're about a mile more than they should be. In fact mileages are via Bristol TM and they weren't recalculated when the Berks and Hants line opened (similarly mileages in South Wales are via Gloucester and weren't recalculated when the Severn Tunnel opened).

The Gunnislake branch is another curiosity, for St. Budeaux Victoria Road to Bere Alston has mileage from Waterloo. Bere Alston to Gunnislake has the former as milepost zero - the Callington branch was originally a separate company the P.D. & S.W.J. Rly. If Tavistock ever reopens will it be given a Waterloo mileage?

 

[Mr. SW]

Searching through near 200-year-old documents just to cross out an old number and put in new would seem a futile exercise to me.

 

[steamybrian]

Mileages on the line from Birchden Jn to Uckfield were originally measured from Brighton via Lewes. After closure of the Uckfield to Lewes line in 1969 they remained until changed in the 1980s when the mileposts to Uckfield were changed and remeasured from London.
For those travelling on the 5 mile Spa Valley Railway. The original mileposts are still preserved between Tunbridge Wells West to Groombridge Junction measured from London via Three Bridges and East Grinstead. Between Groombridge Junction and Birchden Junction measured from Brighton via Lewes. From Birchden Junction to Eridge measured from London via Oxted.

== Doublepost prevention - post automatically merged: 22 Jun 2026 ==

 

[Ian Umpleby]

Is there any reason why mileages/mileposts along a route where the former "zero point" was on a route now closed and abandoned aren't re–measured or replotted?

I quote as one example the Talerddig Loop on the Cambrian Lines, which the Accident Report recently published by RAIB refers to as "being measured from a zero point near Whitchurch on the closed Oswestry route" – I would have thought that the Cambrian Line could have a zero datum redesignated as "Sutton Bridge Junction".

. . .Incidentally when a route is closed and subsequently lifted, are the old/former mileposts normally removed at the time of closure?

== Doublepost prevention - post automatically merged: 22 Jun 2026 ==

I can understand it not being done when B.R.'s Sectional Appendices had to be typeset and written/drawn by hand, but in these days the Sectional Appendices are produced (I believe!) in Adobe Illustrator and wouldn't be a vast amount of work to amend as the old printed B.R. Books were!

Am I being over–simplistic here?

When the line's European Signalling System was implemented everything was made metric, distances and speeds, the latter still present today.
A zero kilometre point was created at the Zero MP by Sutton Bridge Jn and the series extended all the way to Aberystwyth with kilometre posts at (if I recall correctly) half/full kilometre points. Some years later it was decided that the kilometre posts were not needed and the heads were chopped off, but an attached sticker still showed the appropriate km distance. I'm not sure if any still remain.

 

[Chrius56000]

The other question I have remaining is, were old mileposts removed after a line was closed/lifted/abandoned or are they just left to disappear in the undergrowth?

Most pictures of closed/abandoned lines I've seen don't seem to have any – where part of an abandoned line is built over for housing/tin sheds, etc., there would obviously be gaps at those places even if they were left!

Opinions?

 

[zwk500]

The other question I have remaining is, were old mileposts removed after a line was closed/lifted/abandoned or are they just left to disappear in the undergrowth?

Most pictures of closed/abandoned lines I've seen don't seem to have any – where part of an abandoned line is built over for housing/tin sheds, etc., there would obviously be gaps at those places even if they were left!

Opinions?

Many mileposts disappeared into the undergrowth when lines were still open! I suspect that mileposts were not worth the time or effort of the contractors to recover, and any still in place by the time lines closed were simply left there, either rotting, swallowed by foliage, or purloined by souvenir hunters. The contractors will have been interested in the metal and sleepers, mileposts would have little scrap or resale value.

I think, but won't be able to find the entry now, that some heritage railways have been able to recover original mileposts from the trackside when re-opening them back up.

 

[The exile]

The contractors will have been interested in the metal and sleepers, mileposts would have little scrap or resale value.

But enough to encourage a little local “enterprise” - add in the army of collectors of railway memorabilia and it’s hardly surprising they “disappeared”.

 

[Mcr Warrior]

But enough to encourage a little local “enterprise” - add in the army of collectors of railway memorabilia and it’s hardly surprising they “disappeared”.

Do the more valuable mileposts tend to be cast iron or concrete?

 

[Lockwood]

If there is a route from that calls at A, B, C. Its mileage is done from a route that no longer exists. I don't know, they built a bridge/tunnel between A and B that knocked many miles off the route.
Fine, the mileages at B and C are "wrong", but they are fixed, known, accepted, etc.

A new branch is built from B to D.

I am assuming that the convention would be for that to follow the existing mileage convention? So the mileages continue to increase, rather than snapping back to a lower number?

 

[stuu]

The Belfast to Bangor line was re-mileposted with the zero at Dublin Connolly (instead of Belfast Queen's Quay) when the Belfast Central Railway reopened in the 1970s (I've always wondered whether there was any political controversy around that, given the characteristics of North Down...). Presumably the justification was that it would be operating as an extension of the Portadown-Lisburn-Belfast corridor, so it was convenient for it to have common mileages.

I imagine it wasn't publicised widely at the time, whilst now it would be all over social media and a definite sign that Republic is taking over

 

[MarkyT]

If there is a route from that calls at A, B, C. Its mileage is done from a route that no longer exists. I don't know, they built a bridge/tunnel between A and B that knocked many miles off the route.
Fine, the mileages at B and C are "wrong", but they are fixed, known, accepted, etc.

A new branch is built from B to D.

I am assuming that the convention would be for that to follow the existing mileage convention? So the mileages continue to increase, rather than snapping back to a lower number?

You could rebase from zero at the junction, or continue the mainline mileage. If the new branch was surveyed in metres, then starting from 0 at the junction is likely necessary, giving a clear position at which the units change.

 

[Big Jumby 74]

For my penneth, given I, like others here, was on the job pre computer days for many years, any such changes to on the ground measurements, if followed through to what might be called an 'ideal' reflection of same in the paperwork/records, would often mean the prospect of mountains of work both in the first instance and down stream, which could never be kept up with.

In later days when the 'Quality' marks (ISO 9001 etc, IIRC?) started to become part of numerous procedures and documentation, this became a job creation scheme within many departments. One of my former planning colleagues was one such, for whom this sort of detail excited him, so he became the 'owner' of numerous TPU in house documents, but over time keeping up with all the changes and keeping track of the day job (diagramming) meant that things fell by the wayside to a degree.

I kept a selection of such documents which I updated in relation to primarily stock matters in my time, which always had to reflect cross references to timings, train crew and other related matters.

In essence as someone up thread commented, a line has to be drawn with such detail due for no other reason than the workload potentially involved.

 

[edwin_m]

Many mileposts disappeared into the undergrowth when lines were still open! I suspect that mileposts were not worth the time or effort of the contractors to recover, and any still in place by the time lines closed were simply left there, either rotting, swallowed by foliage, or purloined by souvenir hunters. The contractors will have been interested in the metal and sleepers, mileposts would have little scrap or resale value.

I think, but won't be able to find the entry now, that some heritage railways have been able to recover original mileposts from the trackside when re-opening them back up.

I guess metal ones might have been cut off and taken for scrap, but not concrete.

There was a thread on here a few months back where someone wanted to put up facsimile mileposts on an old railway being restored as an active travel route. With the assistance of large scale mapping I believe they were able to find at least one of the originals (concrete I think).

 

[Taunton]

It's surprising how many of the detailed engineering drawings of lines are still taken from those when the line was constructed.

More so, they are also calibrated in chains. There was discussion and dissatisfaction about this here some years ago, until I pointed out that 1 chain = 22 yards = 66 feet, which is the exact length of Mk1/2 carriages. Envisaging a length of 6 chains as 6 carriage lengths is far easier for a railway engineer than saying it is 122 metres away.

 

[MarkyT]

It's surprising how many of the detailed engineering drawings of lines are still taken from those when the line was constructed.

More so, they are also calibrated in chains. There was discussion and dissatisfaction about this here some years ago, until I pointed out that 1 chain = 22 yards = 66 feet, which is the exact length of Mk1/2 carriages. Envisaging a length of 6 chains as 6 carriage lengths is far easier for a railway engineer than saying it is 122 metres away.

An imperial chain is also just over 20m (20.1168m to be more precise), which is useful for quick approximate conversions. The unit got its name from traditional surveyors' chains manufactured to the length consisting of 100 'links', another imperial unit, and 10 chains make a 'furlong' or an eighth of a mile. Today, metric surveying chains are available in (exactly) 20m length.

 

[D6975]

At least one issue would be where to draw the line. The “lawn” at Paddington was extended some years back meaning that the GW “0” is now several yards behind the buffer stops. Theoretically virtually every milepost on ex-GWR metals therefore “needs” re-siting; but is it really worth it?
All London Underground Km measurements start from 0 at a station no longer served by them. Does it matter?

GWR 0 has never been at Paddington. The reason is that when the lines were built, the mileposts were installed at the correct distance from the original planned position of Pad. Nimbys however staged a protest against the position, and Pad was moved before it was even built! It wasn't much of a victory though, the original position was only a short distance towards Hyde park from the present location.

 

[IrishDave]

At least one issue would be where to draw the line. The “lawn” at Paddington was extended some years back meaning that the GW “0” is now several yards behind the buffer stops. Theoretically virtually every milepost on ex-GWR metals therefore “needs” re-siting; but is it really worth it?
All London Underground Km measurements start from 0 at a station no longer served by them. Does it matter?

GWR 0 has never been at Paddington. The reason is that when the lines were built, the mileposts were installed at the correct distance from the original planned position of Pad. Nimbys however staged a protest against the position, and Pad was moved before it was even built! It wasn't much of a victory though, the original position was only a short distance towards Hyde park from the present location.

Per the Signalling Record Society, since 1863 the Paddington zero is at the former junction/boundary with the Metropolitan Railway:

Great Western Mileages are from London Paddington, the zero point being the Paddington Suburban Tunnel boundary with the Metropolitan Railway.
Paddington opened in 1854, effectively swapping places with Paddington Goods. The connection to the Metropolitan opened in 1863. Not currently known how these developments gave rise to changes in the zero point.

 

[TransportHub]

If a new structure (say a footbridge) is built on a line where the 0 point/datum is on a closed line, especially one where the alignment has been built over, how do engineers measure the new value? Or are new non zero datums made when the original is no longer useable?

 

[etr221]

My understanding over the GWR zero/datum point is that was the property line (so actually the GWR frontage on Praed Street), not the actual end (start) of track, which I think used to be at 0m 3ch, beyond the Lawn (and is now a bit further). Not sure how the SRS datum comes about - by my reckoning it would put the Paddington buffer stops at a negative chainage - but maybe I misunderstand quite where is meant - I certainly don't understand all the (former) junctions around there.

If a new structure (say a footbridge) is built on a line where the 0 point/datum is on a closed line, especially one where the alignment has been built over, how do engineers measure the new value? Or are new non zero datums made when the original is no longer useable?

I think in general things are measured off mileposts/other known points: the zero/datum point is (was) only used in the original setting out, or if a full remeasuring is required - measuring long, many mile, distances is a non-trivial task, not to be undertaken lightly.

 

[Oxfordblues]

In the 1970s when metrication was all the rage and everyone wanted to be more "European" some bright spark at BRBHQ proposed replacing all the mileposts and chain-posts with kilometre posts and 100m-posts. Thankfully one of the old hands took him to one side and quietly explained that the multi-million pound cost would be better spent on some real improvements and the idea was quietly dropped.

 

[zwk500]

If a new structure (say a footbridge) is built on a line where the 0 point/datum is on a closed line, especially one where the alignment has been built over, how do engineers measure the new value? Or are new non zero datums made when the original is no longer useable?

Engineers will take a project site datum that corresponds with the existing mileage from a known position. After all, if you know what the starting position is and how far away from that you are, then you know what the mileage from the zero point is.