Routeing guide, understanding negative easement text, and associated data

[tjr2023]

Dear All,

I have been grappling with the routeing guide data feed and documentation (RSPS5047). My background is programming, maths and logic, and machine assisted formalisation, but I must admit I find the routeing guide to be baffling in many parts.

I am currently looking at negative easement 700884. It states: "Customers travelling to London Maylebone or South Ruislip from or via Reading may not travel via Oxford. This circuitous route easement applies in both directions."

Looking at the blue route map (https://assets.nationalrail.co.uk/e...30a3111be8c58/Blue_route_AS_Metro_map_v26.pdf)
I try to understand what this easement means.

Let's take the simple case: Assume we are travelling **from** Reading, to Marylebone. I can see that going in a loop via Oxford would be quite a detour. So this particular instance of the easement seems understandable. And the ojp at https://www.nationalrail.co.uk/ agrees - the relevant journeys are ruled out.

Now let's consider another instance: Assume we are travelling **via** Reading, to Marylebone. Then the negative easement seems to state that we may not travel via Oxford. This makes sense when starting at stations east of Reading (e.g. Twyford or Maidenhead) - we want to rule out the loop via Oxford. But it makes no sense for journeys that start elsewhere, e.g. Tackley (just north of Oxford). So, for example, the easement seems to rule out: Tackley->Oxford->Reading->Paddington->Marylebone. But this is a very common route. And indeed nationalrail.co.uk DOES allow these routes.

So now I am confused because it seems that the easement doesn't mean what it says.

So how else might we interpret the easement? Perhaps the easement should be read as "Customers travelling to London Maylebone or South Ruislip from or via Reading, may not travel via Oxford (**after having already travelled from/via Reading**)." That is, we imagine that Reading must occur before Oxford for the journey to be ruled out.

This is plausible. Is this how I should interpret the easement???

But then I decide to look at the data feed associated with the easements. Easement 700884 has related records, some of which are:

L	702235	MYB	3
L	702235	OXF	1
L	702235	RDG	4

Ignoring the first 2 columns, we have 3 CRS codes, and "location modifier" numbers. The numbers are interpreted as: 1~include,2~origin,3~destination,4~via.

So these records appear to mean "If MYB is the destination, and if OXF is included in the journey, and if the journey is via RDG, then the easement applies". But this doesn't give any indication that OXF must be found AFTER RDG.

Can anyone help me understand what is going on? In particular:

* How is this easement supposed to be interpreted, so that it matches the "official" interpretation at nationalrail.co.uk (when searching for journeys)?
* How do the routeing data feed records relate to this interpretation?

Yours confusedly

Tom

 

[Bletchleyite]

Tackley-Oxford-Reading-Paddington-Marylebone doesn't apply the Routeing Guide for the last bit as that's a Tube transfer (and isn't valid on a London Terminals ticket, you'd need a ticket to London Zone 1, which is in effect a single to London Terminals with a Zone 1 Tube single issued together on one ticket). Thus such a journey isn't "to London Marylebone" in the sense of the Routeing Guide, it's to London Terminals (Paddington), with an effectively separate Tube journey happening to be included in the ticket.

 

[tjr2023]

Tackley-Oxford-Reading-Paddington-Marylebone doesn't apply the Routeing Guide for the last bit as that's a Tube transfer (and isn't valid on a London Terminals ticket, you'd need a ticket to London Zone 1, which is in effect a single to London Terminals with a Zone 1 Tube single issued together on one ticket). Thus such a journey isn't "to London Marylebone" in the sense of the Routeing Guide, it's to London Terminals (Paddington), with an effectively separate Tube journey happening to be included in the ticket.

So the easement interpretation of "journey to London Marylebone" is that the journey has a final leg by rail that ends at Marylebone, and that final transfers by tube to Marylebone would not fall under this interpretation.

That makes sense. Thank you.

 

[MrJeeves]

You may find eNRG Browser useful: https://enrgbrowser.com/easements/700884

 

[Watershed]

So the easement interpretation of "journey to London Marylebone" is that the journey has a final leg by rail that ends at Marylebone, and that final transfers by tube to Marylebone would not fall under this interpretation.

That makes sense. Thank you.

Yes, that's correct. The Routeing Guide generally only applies to the "National Rail" element of any journey, although defining that can be somewhat messy when it comes to the Elizabeth line/Thameslink through central London, or routes where Underground and National Rail tickets are interavailable...

 

[tjr2023]

You may find eNRG Browser useful: https://enrgbrowser.com/easements/700884

Interesting! I was not aware of this site! Much more readable than the raw data.