Discussion:
Max changes on the same line?
(too old to reply)
Ian Clifton
2019-03-28 11:45:53 UTC
Permalink
Let’s suppose you’re going from Reading to Hanwell. You might have to
make as many as 2 changes (at Slough, and Hayes & Harlington), to reach
a station you’d simply pass through if you didn’t change. What’s the
most such changes a (sensible & perfectly informed) passenger ever has
to make?
--
Ian ◎
Theo
2019-03-28 16:52:00 UTC
Permalink
Post by Ian Clifton
Let’s suppose you’re going from Reading to Hanwell. You might have to
make as many as 2 changes (at Slough, and Hayes & Harlington), to reach
a station you’d simply pass through if you didn’t change. What’s the
most such changes a (sensible & perfectly informed) passenger ever has
to make?
I assume doubling back isn't allowed, otherwise you could do that in one
(changing at Paddington)?

Travelling on a Sunday in the winter, try Bourg St Maurice to Stratford
International. I make 5 changes:

Bourg St Maurice - Moutiers-Salins-Bride-les-Bains - Paris Gare de Lyon -
Chatelet les Halles - Paris Gare du Nord - Ashford/Ebbsfleet International -
Stratford International

(on weekdays the ski train stops at Ashford. I don't know if there are
direct trains from Moutiers to Lille in the winter which would cut the
changes to 3)

Theo
Richard J.
2019-03-29 00:48:07 UTC
Permalink
Post by Theo
Post by Ian Clifton
Let’s suppose you’re going from Reading to Hanwell. You might have to
make as many as 2 changes (at Slough, and Hayes & Harlington), to reach
a station you’d simply pass through if you didn’t change. What’s the
most such changes a (sensible & perfectly informed) passenger ever has
to make?
I assume doubling back isn't allowed, otherwise you could do that in one
(changing at Paddington)?
Travelling on a Sunday in the winter, try Bourg St Maurice to Stratford
Bourg St Maurice - Moutiers-Salins-Bride-les-Bains - Paris Gare de Lyon -
Chatelet les Halles - Paris Gare du Nord - Ashford/Ebbsfleet International -
Stratford International
(on weekdays the ski train stops at Ashford. I don't know if there are
direct trains from Moutiers to Lille in the winter which would cut the
changes to 3)
Theo
A "sensible & perfectly informed passenger" would know that you can get from Gare de Lyon to Gare du Nord by RER D without the need to change at Châtelet-Les-Halles.
--
Richard J.
(to email me, swap 'uk' and 'yon' in address)
Ian Clifton
2019-03-29 12:09:46 UTC
Permalink
on 28 Mar 2019 at 16:52 ...
Post by Theo
Post by Ian Clifton
Let’s suppose you’re going from Reading to Hanwell. You might have to
make as many as 2 changes (at Slough, and Hayes & Harlington), to reach
a station you’d simply pass through if you didn’t change. What’s the
most such changes a (sensible & perfectly informed) passenger ever has
to make?
I assume doubling back isn't allowed, otherwise you could do that in one
(changing at Paddington)?
Travelling on a Sunday in the winter, try Bourg St Maurice to Stratford
Bourg St Maurice - Moutiers-Salins-Bride-les-Bains - Paris Gare de Lyon -
Chatelet les Halles - Paris Gare du Nord - Ashford/Ebbsfleet International -
Stratford International
(on weekdays the ski train stops at Ashford. I don't know if there are
direct trains from Moutiers to Lille in the winter which would cut the
changes to 3)
Theo
A "sensible & perfectly informed passenger" would know that you can
get from Gare de Lyon to Gare du Nord by RER D without the need to
change at Châtelet-Les-Halles.
I think I intended something like Theo’s solution to be valid. But
you’re right, in that calling my Passenger “sensible” is inadequate and
probably misleading. A sensible person would probably make a longer or
more expensive journey, rather than endure the faff of many
changes. Maybe it’s better to make him an automaton: the Passenger
always boards the very next train that gets him at all closer to the
destination (even if a following train would get him closer still, or
would reduce the subsequent changes required).
--
Ian ◎
Theo
2019-03-29 16:35:53 UTC
Permalink
Post by Ian Clifton
Post by Richard J.
A "sensible & perfectly informed passenger" would know that you can
get from Gare de Lyon to Gare du Nord by RER D without the need to
change at Châtelet-Les-Halles.
Apologies, I think I misremembered a change.
(Also, I have a feeling there are through trains from Bourg to northern
FR/BE/NL in the winter, which might skew things somewhat)
Post by Ian Clifton
I think I intended something like Theo’s solution to be valid. But
you’re right, in that calling my Passenger “sensible” is inadequate and
probably misleading. A sensible person would probably make a longer or
more expensive journey, rather than endure the faff of many
changes. Maybe it’s better to make him an automaton: the Passenger
always boards the very next train that gets him at all closer to the
destination (even if a following train would get him closer still, or
would reduce the subsequent changes required).
That would make it quite sensitive to time of day and service pattern, which
would make the challenge rather fragile.

Freedom to pick any train on a given day might make sense - the traveller
can start at 00.01 and take any combination of trains that gets them there
by closedown the next morning. But they can't wait for the one through
train a week. Or you could look at trains with a regular service pattern -
perhaps the last train is an all-stations stopper, but during the daytime
you'd have to change.

The next question is whether the passenger must travel on the same line as
the through train, or whether they can take an alternative route (in my
example, you'd probably have to use the around-Paris HSL rather than going
into Gare de Lyon). I'd suggest the station should be one passed through by
the through train, but they passenger need not take the same route to get
there. (So for Inverness to Finsbury Park the traveller could
change at Stevenage and take the Hertford Loop).

Theo
John Williamson
2019-03-29 13:35:54 UTC
Permalink
on  28 Mar 2019 at 16:52 ...
Post by Theo
Travelling on a Sunday in the winter, try Bourg St Maurice to Stratford
Bourg St Maurice - Moutiers-Salins-Bride-les-Bains - Paris Gare de Lyon -
Chatelet les Halles - Paris Gare du Nord - Ashford/Ebbsfleet
International -
Stratford International
(on weekdays the ski train stops at Ashford.  I don't know if there are
direct trains from Moutiers to Lille in the winter which would cut the
changes to 3)
Theo
A "sensible & perfectly informed passenger" would know that you can get
from Gare de Lyon to Gare du Nord by RER D without the need to change at
Châtelet-Les-Halles.
I read the original post as applying to journeys on a single line, not
one where you change lines on the way.

So if the only train you can catch at your local station doesn't stop
where you want to get to, but there is a station where both trains stop,
you have to change trains.

As such, you should never need to change trains on the Underground short
of a service problem on the District, Circle and Hammersmith and City
lines, where they occasional change a Circle line train to H&S, stopping
short. (Probably not the only place it can happen, but it caught me out
recently, and ignoring the length where the Picadilly and District
lines run on parallel tracks, but share some stations. I count those as
different lines.)
--
Tciao for Now!

John.
Ian Clifton
2019-03-29 16:48:32 UTC
Permalink
Post by John Williamson
to on  28 Mar 2019 at 16:52 ...
Post by Theo
Travelling on a Sunday in the winter, try Bourg St Maurice to Stratford
Bourg St Maurice - Moutiers-Salins-Bride-les-Bains - Paris Gare de Lyon -
Chatelet les Halles - Paris Gare du Nord - Ashford/Ebbsfleet
International -
Stratford International
(on weekdays the ski train stops at Ashford.  I don't know if there are
direct trains from Moutiers to Lille in the winter which would cut the
changes to 3)
Theo
A "sensible & perfectly informed passenger" would know that you can
get from Gare de Lyon to Gare du Nord by RER D without the need to
change at Châtelet-Les-Halles.
I read the original post as applying to journeys on a single line, not
one where you change lines on the way.
Yes, that’s what I meant, at first. This all came from a genuine journey
I was planning (Oxford to Hanwell), I came up with the two‐change
journey myself and then decided to see what Network Rail’s Journey
Planner made of it. I thought the Journey Planner would always come up
with a boring but “sensible” one change plan, and was slightly surprised
when it came up with the double change plan too (only for certain
departure times, of course). I then began to wonder if a higher number
of changes could ever be required, and thought this might happen where
several different services (partly) share the same route. But I’m
struggling to make the conditions of the puzzle really concrete.

[...]
--
Ian ◎
Roland Perry
2019-03-30 12:25:04 UTC
Permalink
I’m struggling to make the conditions of the puzzle really concrete.
I'm tempted to say "don't you just love it when civilians try to be
policy wonks".

But the question as posed was almost tightly enough drawn nevertheless.

My own reservations were only about whether doubling back (thus
requiring perhaps specialised ticketing) was allowed as part of the
challenge, as well as enforced overnight - or even longer - layovers.

For example, Denton to Reddish South, which until recently took a week
with two double-backs, if we stick to the "on the same line" rule.
--
Roland Perry
Guy Gorton
2019-03-30 12:51:57 UTC
Permalink
On Fri, 29 Mar 2019 16:48:32 +0000, Ian Clifton
Post by John Williamson
to on  28 Mar 2019 at 16:52 ...
Post by Theo
Travelling on a Sunday in the winter, try Bourg St Maurice to Stratford
Bourg St Maurice - Moutiers-Salins-Bride-les-Bains - Paris Gare de Lyon -
Chatelet les Halles - Paris Gare du Nord - Ashford/Ebbsfleet International -
Stratford International
(on weekdays the ski train stops at Ashford.  I don't know if there are
direct trains from Moutiers to Lille in the winter which would cut the
changes to 3)
Theo
A "sensible & perfectly informed passenger" would know that you can
get from Gare de Lyon to Gare du Nord by RER D without the need to
change at Châtelet-Les-Halles.
I read the original post as applying to journeys on a single line, not
one where you change lines on the way.
Yes, that’s what I meant, at first. This all came from a genuine journey
I was planning (Oxford to Hanwell), I came up with the two?change
journey myself and then decided to see what Network Rail’s Journey
Planner made of it. I thought the Journey Planner would always come up
with a boring but “sensible” one change plan, and was slightly surprised
when it came up with the double change plan too (only for certain
departure times, of course). I then began to wonder if a higher number
of changes could ever be required, and thought this might happen where
several different services (partly) share the same route. But I’m
struggling to make the conditions of the puzzle really concrete.
[...]
I had a look at my line, the Chiltern. Possible journey Brum Moor
Street to one of the stations between South Ruislip and Wembley. The
timetable sites insisted that I go beyond my destination and double
back at either Wembley or Marylebone. I decided I could not be
bothered to look up detail timetables - sorry to be so idle.

Guy Gorton
Basil Jet
2019-03-30 14:19:35 UTC
Permalink
Post by Guy Gorton
I had a look at my line, the Chiltern. Possible journey Brum Moor
Street to one of the stations between South Ruislip and Wembley. The
timetable sites insisted that I go beyond my destination and double
back at either Wembley or Marylebone. I decided I could not be
bothered to look up detail timetables - sorry to be so idle.
So the timetable sites refuse to give the cheapest route... not good!
--
Basil Jet - Current favourite song...
Spratleys Japs - Hands (Marc Riley session)

Roland Perry
2019-03-30 14:54:47 UTC
Permalink
Post by Basil Jet
Post by Guy Gorton
I had a look at my line, the Chiltern. Possible journey Brum Moor
Street to one of the stations between South Ruislip and Wembley. The
timetable sites insisted that I go beyond my destination and double
back at either Wembley or Marylebone. I decided I could not be
bothered to look up detail timetables - sorry to be so idle.
So the timetable sites refuse to give the cheapest route... not good!
Not an issue I see here. One change at Gerrards Cross or High Wycombe,
and nowhere near Marylebone.
--
Roland Perry
Recliner
2019-03-30 15:41:03 UTC
Permalink
Post by John Williamson
on  28 Mar 2019 at 16:52 ...
Post by Theo
Travelling on a Sunday in the winter, try Bourg St Maurice to Stratford
Bourg St Maurice - Moutiers-Salins-Bride-les-Bains - Paris Gare de Lyon -
Chatelet les Halles - Paris Gare du Nord - Ashford/Ebbsfleet
International -
Stratford International
(on weekdays the ski train stops at Ashford.  I don't know if there are
direct trains from Moutiers to Lille in the winter which would cut the
changes to 3)
Theo
A "sensible & perfectly informed passenger" would know that you can get
from Gare de Lyon to Gare du Nord by RER D without the need to change at
Châtelet-Les-Halles.
I read the original post as applying to journeys on a single line, not
one where you change lines on the way.
So if the only train you can catch at your local station doesn't stop
where you want to get to, but there is a station where both trains stop,
you have to change trains.
As such, you should never need to change trains on the Underground short
of a service problem on the District, Circle and Hammersmith and City
lines, where they occasional change a Circle line train to H&S, stopping
short. (Probably not the only place it can happen, but it caught me out
recently, and ignoring the length where the Picadilly and District
lines run on parallel tracks, but share some stations. I count those as
different lines.)
What about the Metropolitan line, that has Fast, Semi-fast and All-stops
services? So, for example, if you board a fast train from Chalfont,
wanting to travel to Nothwick Park, you'd need to change to a stopper ar
Harrow-on-the-Hill.
bob
2019-04-01 20:57:41 UTC
Permalink
Post by Ian Clifton
Let’s suppose you’re going from Reading to Hanwell. You might have to
make as many as 2 changes (at Slough, and Hayes & Harlington), to reach
a station you’d simply pass through if you didn’t change. What’s the
most such changes a (sensible & perfectly informed) passenger ever has
to make?
How about something like Thirsk - York - Peterborough - Stevenage - Welwyn
North?

Robin
Roland Perry
2019-04-02 07:39:41 UTC
Permalink
Post by bob
Post by Ian Clifton
Let’s suppose you’re going from Reading to Hanwell. You might have to
make as many as 2 changes (at Slough, and Hayes & Harlington), to reach
a station you’d simply pass through if you didn’t change. What’s the
most such changes a (sensible & perfectly informed) passenger ever has
to make?
How about something like Thirsk - York - Peterborough - Stevenage - Welwyn
North?
Apart from there being a regular service from York to Stevenage, meaning
two changes eminently possible.

Journey planners also offer the occasional one-change, at Kings Cross.
Which goes back to my earlier question about how challenges like this
interact with doubling-back.

Sun-Fri Shippea Hill to Ely[1], for example, always requires doubling
back; but still results in only two changes.

[1] And of course anywhere further east on that line, *to* Shippea Hill.
--
Roland Perry
bob
2019-04-02 19:01:22 UTC
Permalink
Post by Roland Perry
Post by bob
Post by Ian Clifton
Let’s suppose you’re going from Reading to Hanwell. You might have to
make as many as 2 changes (at Slough, and Hayes & Harlington), to reach
a station you’d simply pass through if you didn’t change. What’s the
most such changes a (sensible & perfectly informed) passenger ever has
to make?
How about something like Thirsk - York - Peterborough - Stevenage - Welwyn
North?
Apart from there being a regular service from York to Stevenage, meaning
two changes eminently possible.
I obviously didn’t do my timetable checking properly, but I think the
concept is clear enough: Stevenage has a limited set of stations north of
Peterborough that are directly served, and Welwyn North has no direct
service to Peterborough, so pick a station up the ECML not served from
Stevenage with a station beyond not served directly by either Stevenage or
Peterborough, but where direct Anglo-Scottish services pass directly
through.
Post by Roland Perry
Journey planners also offer the occasional one-change, at Kings Cross.
Which goes back to my earlier question about how challenges like this
interact with doubling-back.
Doubling back makes finding examples much harder.

Robin
Roland Perry
2019-04-02 19:13:02 UTC
Permalink
Post by bob
Post by Roland Perry
Post by bob
Post by Ian Clifton
Let’s suppose you’re going from Reading to Hanwell. You might have to
make as many as 2 changes (at Slough, and Hayes & Harlington), to reach
a station you’d simply pass through if you didn’t change. What’s the
most such changes a (sensible & perfectly informed) passenger ever has
to make?
How about something like Thirsk - York - Peterborough - Stevenage - Welwyn
North?
Apart from there being a regular service from York to Stevenage, meaning
two changes eminently possible.
I obviously didn’t do my timetable checking properly, but I think the
concept is clear enough: Stevenage has a limited set of stations north of
Peterborough that are directly served, and Welwyn North has no direct
service to Peterborough, so pick a station up the ECML not served from
Stevenage with a station beyond not served directly by either Stevenage or
Peterborough, but where direct Anglo-Scottish services pass directly
through.
That only produces a fairly long list of 2-change scenarios. I think we
ought to be aiming for 3+
Post by bob
Post by Roland Perry
Journey planners also offer the occasional one-change, at Kings Cross.
Which goes back to my earlier question about how challenges like this
interact with doubling-back.
Doubling back makes finding examples much harder.
I'm wondering that (if allowed as a strategy) we might find
circumstances where it 'adds one' to the list.
--
Roland Perry
bob
2019-04-02 21:58:43 UTC
Permalink
Post by Roland Perry
Post by bob
Post by Roland Perry
Post by bob
Post by Ian Clifton
Let’s suppose you’re going from Reading to Hanwell. You might have to
make as many as 2 changes (at Slough, and Hayes & Harlington), to reach
a station you’d simply pass through if you didn’t change. What’s the
most such changes a (sensible & perfectly informed) passenger ever has
to make?
How about something like Thirsk - York - Peterborough - Stevenage - Welwyn
North?
Apart from there being a regular service from York to Stevenage, meaning
two changes eminently possible.
I obviously didn’t do my timetable checking properly, but I think the
concept is clear enough: Stevenage has a limited set of stations north of
Peterborough that are directly served, and Welwyn North has no direct
service to Peterborough, so pick a station up the ECML not served from
Stevenage with a station beyond not served directly by either Stevenage or
Peterborough, but where direct Anglo-Scottish services pass directly
through.
That only produces a fairly long list of 2-change scenarios. I think we
ought to be aiming for 3+
It appears I overlooked the one per day each way King’s Cross - Aberdeen
services that call at Stevenage, I’d been working on the assumption all
Stevenage trains were Yorkshire only, that would make Stevenage - Newcastle
or Edinburgh impossible without a change. That would have made stations
north of Newcastle only served by Northern into 3 changers.

Thinking a little further afield, start with the Eurostar Amsterdam
service. This calls at StP, Brussels, Rotterdam Centraal and Amsterdam
Centraal. Take Stratford International and Rotterdam Zuid, both of which
the Eurostar passes through. Disallowing doubling back, the best I can
figure is Stratford International - Ebbsfleet - Brussels Midi - Breda -
Dordrecht - Rotterdam Zuid. From what I can tell this is possible to do
without deviating from the route followed by the through train, and doesn’t
involve spurious extra changes other than those needed to avoid doubling
back.

Robin
bob
2019-04-02 22:09:49 UTC
Permalink
Post by bob
Post by Roland Perry
Post by bob
Post by Roland Perry
Post by bob
Post by Ian Clifton
Let’s suppose you’re going from Reading to Hanwell. You might have to
make as many as 2 changes (at Slough, and Hayes & Harlington), to reach
a station you’d simply pass through if you didn’t change. What’s the
most such changes a (sensible & perfectly informed) passenger ever has
to make?
How about something like Thirsk - York - Peterborough - Stevenage - Welwyn
North?
Apart from there being a regular service from York to Stevenage, meaning
two changes eminently possible.
I obviously didn’t do my timetable checking properly, but I think the
concept is clear enough: Stevenage has a limited set of stations north of
Peterborough that are directly served, and Welwyn North has no direct
service to Peterborough, so pick a station up the ECML not served from
Stevenage with a station beyond not served directly by either Stevenage or
Peterborough, but where direct Anglo-Scottish services pass directly
through.
That only produces a fairly long list of 2-change scenarios. I think we
ought to be aiming for 3+
It appears I overlooked the one per day each way King’s Cross - Aberdeen
services that call at Stevenage, I’d been working on the assumption all
Stevenage trains were Yorkshire only, that would make Stevenage - Newcastle
or Edinburgh impossible without a change. That would have made stations
north of Newcastle only served by Northern into 3 changers.
Thinking a little further afield, start with the Eurostar Amsterdam
service. This calls at StP, Brussels, Rotterdam Centraal and Amsterdam
Centraal. Take Stratford International and Rotterdam Zuid, both of which
the Eurostar passes through. Disallowing doubling back, the best I can
figure is Stratford International - Ebbsfleet - Brussels Midi - Breda -
Dordrecht - Rotterdam Zuid. From what I can tell this is possible to do
without deviating from the route followed by the through train, and doesn’t
involve spurious extra changes other than those needed to avoid doubling
back.
Looking at a map, it looks like the HS line that Eurostar uses skirts the
edges of Breda and Dordrecht bypassing the stations themselves, but without
deviating into those two places, there is no method of avoiding doubling
back.

Robin
Roland Perry
2019-04-03 12:16:17 UTC
Permalink
Post by bob
Post by Roland Perry
Post by bob
Post by Roland Perry
Post by bob
Post by Ian Clifton
Let’s suppose you’re going from Reading to Hanwell. You might have to
make as many as 2 changes (at Slough, and Hayes & Harlington), to reach
a station you’d simply pass through if you didn’t change. What’s the
most such changes a (sensible & perfectly informed) passenger ever has
to make?
How about something like Thirsk - York - Peterborough - Stevenage - Welwyn
North?
Apart from there being a regular service from York to Stevenage, meaning
two changes eminently possible.
I obviously didn’t do my timetable checking properly, but I think the
concept is clear enough: Stevenage has a limited set of stations north of
Peterborough that are directly served, and Welwyn North has no direct
service to Peterborough, so pick a station up the ECML not served from
Stevenage with a station beyond not served directly by either Stevenage or
Peterborough, but where direct Anglo-Scottish services pass directly
through.
That only produces a fairly long list of 2-change scenarios. I think we
ought to be aiming for 3+
It appears I overlooked the one per day each way King’s Cross - Aberdeen
services that call at Stevenage,
There's several Edinburgh services which call at both Newcastle and
Stevenage.
Post by bob
I’d been working on the assumption all
Stevenage trains were Yorkshire only, that would make Stevenage - Newcastle
or Edinburgh impossible without a change. That would have made stations
north of Newcastle only served by Northern into 3 changers.
If most pairs of LNER stations have at least one direct service between
them per day, then we'll struggle to find any 3-change journeys on the
ECML.
Post by bob
Thinking a little further afield, start with the Eurostar Amsterdam
service. This calls at StP, Brussels, Rotterdam Centraal and Amsterdam
Centraal. Take Stratford International and Rotterdam Zuid, both of which
the Eurostar passes through. Disallowing doubling back, the best I can
figure is Stratford International - Ebbsfleet - Brussels Midi - Breda -
Dordrecht - Rotterdam Zuid. From what I can tell this is possible to do
without deviating from the route followed by the through train, and doesn’t
involve spurious extra changes other than those needed to avoid doubling
back.
South of France E* must be another to look at.
--
Roland Perry
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