Routeing point groups and shortest routes on local journey legs.

[JB_B]

When applying the shortest route (+ up to 3 mile margin ) rule for the local part of a journey to an origin routeing point where the origin routeing point is a group , should I apply the rule separately for each group member or should I base the +3 mile margin only on the distance to the nearest member.


Example: Suppose I'm starting from Perry Barr to a destination where Birmingham Group is the only valid origin routing point.

PRY WTT AST at 1.56m is the shortest route to the nearest group member (AST).
PRY WTT AST DUD BHM at 4.40m is the shortest route to another member (BHM)

Can I use...

PRY HSD BHM at 7.12m (it's within three miles of shortest route to BHM but more than three miles over the distance to AST) ?

( I haven't checked if there are any local rules that make this a poor example - hopefully it's enough to explain the general question at least. )

AST = Aston *
BHM = Birmingham New Street *
DUD = Duddeston *
HSD = Hamstead
PRY = Perry Barr
WTT = Witton WM

(* = Birmingham Routeing Point Group Members - the others are Snow Hill and Moor Street )

 

[yorkie]

When applying the shortest route (+ up to 3 mile margin ) rule for the local part of a journey to an origin routeing point where the origin routeing point is a group , should I apply the rule separately for each group member or should I base the +3 mile margin only on the distance to the nearest member.


Example: Suppose I'm starting from Perry Barr to a destination where Birmingham Group is the only valid origin routing point.

PRY WTT AST at 1.56m is the shortest route to the nearest group member (AST).
PRY WTT AST DUD BHM at 4.40m is the shortest route to another member (BHM)

As Aston is the first station you encounter in the Group, then you use Aston as your Origin Routeing Point, for the above calculation (but I think you already know that)

Can I use...

PRY HSD BHM at 7.12m (it's within three miles of shortest route to BHM but more than three miles over the distance to AST) ?

This is, I believe, a theoretical question, as I don't think there is any train in the current timetable that goes non-stop from HSD to BHM direct, avoiding Aston.

However, if such a service did exist, then the fact Aston is a member of Birmingham Group would be an irrelevance to the calculation. You would be calculating the mileage from the origin station to the relevant member of the routeing group, in this case BHM, and as long as that distance is within 3 miles, which it is, you're fine.

We would never compare mileages to Aston vs mileages to Birmingham New Street.

 

[JB_B]

Thanks, Yorkie.

That makes sense ( I must admit I didn't realize that all HSD to BHM trains are routed via AST anyway.)

So I think I need to do the shortest route calculation separately for each group member and then expand out to +3 miles from the origin to that member (but I don't need to consider group members which cannot be reached without passing through another group member first.)

 

[yorkie]

So I think I need to do the shortest route calculation separately for each group member and then expand out to +3 miles from the origin to that member (but I don't need to consider group members which cannot be reached without passing through another group member first.)

Agreed.

But be careful; I think I recall there are some examples of where RDG's Routeing Point Calculator claims that an RP "cannot be reached without passing another member of the group" but it is actually possible to do so, but I can't think of any examples right now.

 

[JB_B]

That's a good point - when applying it's (entirely imaginary) fare-check-only-at-first-group-member-reached 'rule', rp_calc seems to make unwarranted assumptions about the route taken into the group.

( See e.g. https://www.railforums.co.uk/thread...teing-point-group-member.152577/#post-3106376 )

For the shortest-route rule I think it's a different case and it's sometimes justifiable to discount certain group members (e.g. Portsmouth and Southsea can be ignored for Portsmouth Group) as that will never yield a shorter route into the group.)

 

[kieron]

But be careful; I think I recall there are some examples of where RDG's Routeing Point Calculator claims that an RP "cannot be reached without passing another member of the group" but it is actually possible to do so, but I can't think of any examples right now.

Stratford International is an example for most (if not all) routes where it appears in the fare check. It isn't listed in the published NFM64 data, so isn't a valid routeing point if you use the published rules.

Acton Bridge-Manchester Piccadilly is another one. Warrington Central is a valid routeing point for Acton Bridge, but the routeing point calculator says you need to pass through another station in the group. It may also be a journey where (at least some) ticket sites show the shortest route as not being a valid route.