Would anybody be able to confirm if my understanding here is correct ?
According to the spec for online routeing engines:
"The Local Journey is permitted if"
" the Local Journey is via the shortest route.
the Local Journey is via the shortest route except for deviations via stations which are in the same station-group as a station on the shortest route.
the length of the Local Journey is within a specified margin of the length of the shortest route"
"Journey within allowed margin of shortest route
The Local Journey is permitted if the distance of the actual journey is within a specified margin of the distance of the shortest route, if an allowed margin has been specified.
Any deviations or double-backs within that station-group should not be included in the distance calculation."
"Deviations within a station-group
Deviations within a station-group are allowed except when the journey origin station or destination station is part of that station-group.
If the Local Journey includes a station which is in the same station-group as any station on the shortest journey (excluding any station-groups containing the origin and destination stations) then this is considered a permitted deviation from the shortest route.
This includes both deviations to stations not on the shortest journey, and double-backs between stations which are on the shortest journey."
Minster and Ramsgate are both part of Ramsgate station-group.
We can measure the shortest route here:
http://www.bukitlawang.com/routes/routes.aspx
Chartham - Bekesbourne has its shortest route according to NRE data, of:
Chartham - Ashford International - Dover Priory - Bekesbourne
at 44.87 miles
The journey
Chartham - Minster 14.63 miles
Minster - Sandwich 4.76 miles
Sandwich - Bekesbourne via Dover 26.02 miles
is thus permitted, being 45.41 miles, and therefore within the permitted margin
If Minster was between Ramsgate and Sandwich, then the journey:
Chartham - Minster - Ramsgate - Dover Priory - Bekesbourne would be classed as a "permitted deviation from the shortest route"
However, Minster is NOT between Ramsgate and Sandwich, and therefore I suspect the distance is being calculated as follows:
Chartham - Minster 14.63 miles
Minster - Ramsgate - free permitted deviation
Ramsgate - Sandwich 8.34 miles
Sandwich - Bekesbourne via Dover 26.02 miles
=48.99 miles
which outside the permitted margin.
If Sandwich were included in the Ramsgate routeing group, then this would work fine.
The NRG btw, states:
"Some stations are grouped together to improve interchange between trains by offering customers access to a wider choice of train services and station facilities. A customer may travel via any station in such a group, including doubling back, provided that the group is on one of the permitted routes between their origin and destination stations. This extended availability is for interchange purposes only and does not apply where the origin or destination stations are part of a group."
Tickets such as Sturry - Deal would be valid via Ramsgate of course, because you can conduct them on a train to and from the common routeing point (Ramsgate).
