Kilometre point 206 on HS1, 206km from where?

[BbCt]

I’ve been driving up and down HS1 since the first section opened in 2003. The now disused Southfleet junction is approximately 40 kilometres from St Pancras yet there is a lonely 206 kilometre point marker on the up line. 206 kilometres from where?

 

[PLY2AYS]

I’ve been driving up and down HS1 since the first section opened In 2003. The now disused Southfleet junction is approximately 40 kilometres from St Pancras yet there is a lonely 206 kilometer point marker on the up line. 206 kilometres from where?

Would it be KMs or miles?
I often think this when driving on the Chiltern Mainline coming in/out of Marylebone where the mileage markers are ~200m (also 206 if memory serves)

 

[Transilien]

Perhaps Somewhere near Lille? That is where the channel tunnel aproach section of the LGV Nord branches off the main route from Paris.

 

[zwk500]

Would it be KMs or miles?

HS1 is KM

I often think this when driving on the Chiltern Mainline coming in/out of Marylebone where the mileage markers are ~200m (also 206 if memory serves)

Mileage on the Chiltern Mainline is measured from Manchester Piccadilly, via Sheffield Victoria as the headquarters of the GCR.

 

[swt_passenger]

Would it be KMs or miles?
I often think this when driving on the Chiltern Mainline coming in/out of Marylebone where the mileage markers are ~200m (also 206 if memory serves)

Chiltern mileages are unusual for a route into a London terminus in not having the zero at the London end, they’re measured from somewhere around Manchester IIRC, start of the GCR.

 

[PLY2AYS]

HS1 is KM

That makes much more sense.

Mileage on the Chiltern Mainline is measured from Manchester Piccadilly, via Sheffield Victoria as the headquarters of the GCR.

Hadn’t appreciated that! Thanks for the insight!

 

[swt_passenger]

I’ve been driving up and down HS1 since the first section opened In 2003. The now disused Southfleet junction is approximately 40 kilometres from St Pancras yet there is a lonely 206 kilometer point marker on the up line. 206 kilometres from where?

Welcome to the forums, by the way…

The short spur with line reference FJS only runs from 200.09 km to 206.0 km, where as far as I can see 206 km is the HS1 end of the link. Railway Codes website reckons the datum point is near Fawkham Junction. I suspect it was just given a round figure above those on the main route as it was considered temporary when built.

The main HS1/CTRL route is measured in km from St Pancras, with an end point of 108 km becoming 7km at the start of the Eurotunnel infrastructure boundary, the 0km point for the Eurotunnel infrastructure is apparently at the abandoned 1974 portal, (according to Quail maps).

 

[stuving]

Welcome to the forums, by the way…

The short spur with line reference FJS only runs from 200.09 km to 206.0 km, where as far as I can see 206 km is the HS1 end of the link. Railway Codes website reckons the datum point is near Fawkham Junction. I suspect it was just given a round figure above those on the main route as it was considered temporary when built.

The main HS1/CTRL route is measured in km towards St Pancras, with a start point at 7km at the Eurotunnel infrastructure boundary, the 0km point for that is apparently at the abandoned 1974 portal, (according to Quail maps).

I'd agree about the distance marking on the Fawkham-Southfleet link, with an arbitrary 200 km drawn on plans at an early stage, and being a few metres out when remeasured as built. But as I read the map, the 7 km reference point is the boundary between CTRL and Eurotunnel, with distances into the tunnel starting at 7 km there. The CTRL side is measured from St Pancras, and is over 108 km at that boundary. Asset labelling does follow that pattern, reaching 80 km at the end of the Lenham Loops (Charing Crossover).

 

[swt_passenger]

But as I read the map, the 7 km reference point is the boundary between CTRL and Eurotunnel, with distances into the tunnel starting at 7 km there. The CTRL side is measured from St Pancras, and is over 108 km at that boundary. Asset labelling does follow that pattern, reaching 80 km at the end of the Lenham Loops (Charing Crossover).

Yes - for some reason I took completely the wrong direction from that drawing … I’ve fixed my post to avoid future confusion…

 

[zwk500]

I'd agree about the distance marking on the Fawkham-Southfleet link, with an arbitrary 200 km drawn on plans at an early stage, and being a few metres out when remeasured as built. But as I read the map, the 7 km reference point is the boundary between CTRL and Eurotunnel, with distances into the tunnel starting at 7 km there. The CTRL side is measured from St Pancras, and is over 108 km at that boundary. Asset labelling does follow that pattern, reaching 80 km at the end of the Lenham Loops (Charing Crossover).

Interestingly Fawkham Jn is shown at 200.091km on the HS1 Sectional Appendix, suggesting the Datum is a bit further back than the junction itself (Possibly the toe of the points, with the junction mileage being measured at a slightly different position, maybe the old signal box?) https://stpancras-highspeed.com/our-company/regulatory/regulatory-docs/

Interestingly the other connecting lines to HS1 either start at 0 from the junction or share the Platform 5-10 Buffers datum of the mainline.
ECML Connection - Continuation of Datum
SILO Curve - New 0 at divergence from ECML Connection (ends at NLL connection)
NLL Connection - New 0 (and reversal of mileage direction) at York Way South Jn
Temple Mills Connection - continuation of Datum
Ripple Lane Chords - Shares Datum, presumably measured back from Dagenham Jns
Ebbsfleet branch - continuatuion of datum

Waterloo Connections: Fawkham Jn - Measured start at 200.091km, KM change at Southfleet Jn. Fawkham Jn's Mileage on the classic lines is VIR 22m51ch.

Ashford West Chords - continuation of datum
Ashford East chords - shares datum, presumably measured back from Ashford East Jn

(and for completeness)
KM change at west end of Dollands Moor (108.582 from ST Pancras/7.000 ET Datum)
HS1/ET Boundary at 8.366

 

[BbCt]

Thanks all - everyday is a school day.
So 2 0 (Fawkham points) + 6 kilometres rather than 206 kilometres.
I‘m slightly disappointed but it makes sense.
Also Chiltern main line measured from Manchester - I didn’t know that.