Greater Anglia Map - Routeing Guide Question - South bound journeys via Ipswitch to Mistley and Harwich Town

[jpickardvs]

I have a question with reference to this map: https://www.greateranglia.co.uk/media/12286/download?inline
With the exception of two daily direct services between Ipswich and Harwich International (via the limited service North to East leg you can see on the map) all other southbound journeys to the "Mistley to Harwich Town" leg require a change at Ipswich then onto Manningtree then a change at Manningtree and then carrying on the journey to any of the stations on the "Mistley to Harwich Town" leg.

For example, if the origin is Westerfield WFI and destination is Mistley MIS then the route involves two changes:
- Westerfield WFI -> Ipswich IPS
- Change at Ipswich IPS
- Ipswich IPS -> Manningtree MNG
- Change at Manningtree MNG
- Manningtree MNG -> Mistley MIS

The principle applies to any stations north of Ipswich e.g. Lowestoft to Harwich Town requires passing through Ipswich, change at Manningtree and onto any of the stations on the Mistley leg.

My question comes around the routeing guide rules for this "journey edge case" - in other words, what is the train terminology/rule that requires onward travel to Manningtree and then what looks like travelling in a reverse direction on towards Mistley. For this scenario I've tried to answer my own questions e.g. how many common routing points are there out of the CRS codes that are in play? Is the change at Manningtree and going back up North to East classed as a "double back".

I would be interested in people's thoughts about the scenario because I've got some software (that uses data from Open Data: Fares, Routeing Guide and Timetable data) and this software can see the following data in the feed about stations WFI (origin) and MIS (destination):

Station identifier: WFI
- Routing point 1 : IPS
- Routing point 2: NWR
- Routing point 3: (null)
- Routing point 4: (null)

Station identifier: MIS
- Routing point 1: IPS
- Routing point 2: MNG
- Routing point 3: (null)
- Routing point 4: (null)

It's not clear in the above data items how/why Manningtree should be a mandatory changing point to get to Mistley. If you go to https://www.nationalrail.co.uk/journey-planner then it correctly identifies that it's not possible to travel direct between Westerfield and Mistley and that two changes are required (change at Ipswich then change again at Manningtree).

Thanks in advance for your help.

 

[Hadders]

Changing at Manningtree is not classed as a double back. A double back occurs if you pass through a station twice.

Permitted routes for a journey are:

- direct trains, in this case there isn't one
- the shortest route by rail (routes upto 3.25 miles in excess of the shortest route are also allowed)
- routes permitted by the routeing guide

Travelling via Manningtree is valid because it is not more than 3.25 more than the shortest route, also a double back isn't involved as you don't pass through a station twice.

 

[jfollows]

Routes under 3.25 miles is not the same as routes within 3 miles, I think the latter is correct and applies here.
The NRT mileage granularity is 0.25 mile I agree.

 

[Hadders]

Routes under 3.25 miles is not the same as routes within 3 miles, I think the latter is correct and applies here.
The NRT mileage granularity is 0.25 mile I agree.

Actually I think you're right - I think it is 3 miles but systems normally use 3.25 miles to account of 'mileage measurement issues'.

Either way, travelling via Manningtree in this case adds less than 3 miles looking at the location of the junction relative to the station.

 

[Watershed]

I think what you're getting at is that under the Routeing Guide, this is considered a 'local journey' - since journeys like Lowestoft to Mistley have Ipswich as a common Routeing Point. That means you can't use mapped routes, and are reliant on the 'within 3 miles of the shortest route' rule to permit travel via Manningtree.

There is nothing in the 'within 3 miles' rule which says that double backs are prohibited. Doubling back is only prohibited in some scenarios - not universally. For this particular case, it's worth noting that you aren't considered to be doubling back merely by passing over the same section of track twice (from Manningtree South Junction to Manningtree station). It is only considered doubling back if you pass through a station more than once.

As this example demonstrates, you can't always work backwards from the Routeing Guide to work out how to construct journeys - rather, you construct journeys first using schedules, and then check whether they are valid for a through ticket using the Routeing Guide.

 

[jpickardvs]

Thanks everyone for your replies so far. Is it correct to say that for WFI -> IPS -> MNG -> MIS (with 2 changes) there is only one single common routing point, that being IPS - and that MNG is not a routing point as such? It's an important question because it may help me solve my problem.

 

[Watershed]

Thanks everyone for your replies so far. Is it correct to say that for WFI -> IPS -> MNG -> MIS (with 2 changes) there is only one single common routing point, that being IPS - and that MNG is not a routing point as such? It's an important question because it may help me solve my problem.

MNG is also a Routeing Point, however it is not used when determining permitted routes for a journey like WFI-MIS since IPS is the only common Routeing Point.

We can probably help you better if you tell us the full details of the problem you are trying to solve.

 

[jpickardvs]

I'll try by using some pseudocode with outcomes for each (some of the outcomes come from my original question around station data that comes from Open Data's routing guide feed).

Pseudocode	Outcome
set origin = "WFI"	origin = "WFI"
set destination = "MIS"	destination = "MIS"
get routing points from Routeing Guide stations data for "WFI"	origin_routingPoints = "IPS", "NWR"
get routing points from Routeing Guide stations data for "MIS"	destination_routingPoints = "IPS", "MNG"
determine the common routing point(s) from origin_routingPoints and destination_routingPoints	commonRoutingPoints = "IPS"
if the number of common routing points is 1 then continue:
determine the shortest route distance between "WFI" and "MIS"	14.01 miles
create a route object using a location list comprised of origin, common routing points and destination - in this case the list is "WFI", "IPS", "MIS"	A valid route to MIS is not possible (the nearest match found is "WFI" to "IPS")

So you can see above that the code throws away "MNG" when attempting to plot a route. The code doesn't know that throwing away "MNG" is a mistake - the code just thinks that single common routing point "IPS" is valid in order to reach "MIS". It is as if the code is not handling a rule (for which I don't know about yet) - a rule that would say "yes, IPS is a common routing point but you must travel to "MNG" and change in order to travel onwards to "MIS" and all the other stations (Wrabness, Harwich International, Dovercourt and terminating at Harwich Town).

I haven't seen any other examples of this route edge case elsewhere on the network in order to see if the code handles those other journeys.

 

[akm]

It is as if the code is not handling a rule (for which I don't know about yet) - a rule that would say "yes, IPS is a common routing point but you must travel to "MNG" and change in order to travel onwards to "MIS" and all the other stations (Wrabness, Harwich International, Dovercourt and terminating at Harwich Town).

I'm slightly at a loss to understand what you're missing here - is your 'get from A to Z' code currently only able to handle the case where A and Z are on the same single piece of track?!

 

[Watershed]

I'll try by using some pseudocode with outcomes for each (some of the outcomes come from my original question around station data that comes from Open Data's routing guide feed).

Pseudocode	Outcome
set origin = "WFI"	origin = "WFI"
set destination = "MIS"	destination = "MIS"
get routing points from Routeing Guide stations data for "WFI"	origin_routingPoints = "IPS", "NWR"
get routing points from Routeing Guide stations data for "MIS"	destination_routingPoints = "IPS", "MNG"
determine the common routing point(s) from origin_routingPoints and destination_routingPoints	commonRoutingPoints = "IPS"
if the number of common routing points is 1 then continue:
determine the shortest route distance between "WFI" and "MIS"	14.01 miles
create a route object using a location list comprised of origin, common routing points and destination - in this case the list is "WFI", "IPS", "MIS"	A valid route to MIS is not possible (the nearest match found is "WFI" to "IPS")

So you can see above that the code throws away "MNG" when attempting to plot a route. The code doesn't know that throwing away "MNG" is a mistake - the code just thinks that single common routing point "IPS" is valid in order to reach "MIS". It is as if the code is not handling a rule (for which I don't know about yet) - a rule that would say "yes, IPS is a common routing point but you must travel to "MNG" and change in order to travel onwards to "MIS" and all the other stations (Wrabness, Harwich International, Dovercourt and terminating at Harwich Town).

I haven't seen any other examples of this route edge case elsewhere on the network in order to see if the code handles those other journeys.

I think there are two issues with your pseudocode here. Firstly, whichever mileage data source it is using should contain the link from Ipswich to Mistley avoiding Manningtree - this is a link that sees a passenger service, as you say.

Secondly, you need to include all of the 'local journey' Routeing Guide rules in full, as well as the easements. In other words, you need to allow routes within 3 miles of the shortest route, not just the absolute shortest route. You also need to allow direct trains to and from a common Routeing Point, as well as routes that 'local' easements (and others) allow. Furthermore, this all assumes you are following the textual, customer-facing version of the Routeing Guide; the version used by journey planners has some differences.

Your code is not wrong for discarding MNG. Since there is a Routeing Point in common (IPS), any Routeing Points that are not in common should be discarded.

 

[Mcr Warrior]

Either way, travelling via Manningtree in this case adds less than 3 miles looking at the location of the junction relative to the station.

Concur. An extra half mile, or so, for a journey from Ipswich to Mistley and beyond, by going the longer way, i.e. doubling back / changing at Manningtree station, rather than using the North curve between Manningtree North Junction and Manningtree East Junction. Think only two trains per day run 'direct' from Ipswich to Harwich International, and neither service calls intermediately at Mistley or Wrabness when operating in that particular direction.

 

[Haywain]

I haven't seen any other examples of this route edge case elsewhere on the network in order to see if the code handles those other journeys.

Just an observation here but you seem to be making a very simple journey look very complicated.

 

[Watershed]

Just an observation here but you seem to be making a very simple journey look very complicated.

I think the OP is developing some code, for which this simply stands as a useful example.