Journey Planner and Clapham Junction Interchange

[zoneking]

I wish to travel between Caterham and Epsom tomorrow morning. Due to engineering work, the preferred route via Norwood Junction is not available. The national rail journey planner suggests going via Clapham Junction (CLJ), which is fine, but then suggests a wait of 38 minutes at CLJ.
This is ridiculous. I understand it uses a 10 minute interchange time, but the train from Purley arrives platform 12, and the train to Epsom leaves from platform 11, the adjacent platform on the same island. So an eight minute interchange should be sufficient in this case to get the 08.18 train. Can the journey planner be sophisticated enough to understand the differences in interchange time between different platforms at the same station?

By the way, there are fewer trains from East Croydon to CLJ tomorrow, and I expect the Purley train to be very crowded, as it is only four coaches.

 

[Hadders]

Journey planners aren’t that sophisticated and not should they be as the platform coukdnchange at the last minute. Journey planners also need to account for people who are unfamiliar with the station layout.

If travelling on a walk on ticket there’s absolutely nothing stopping you from catching the earlier train.

 

[kieron]

There is a way operators can define a different interchange time based on the operator listed for the service. For Clapham Junction, there's a 5 minute minimum interchange between two Southern services, but 10 if you're using Overground or SWR ones on either leg. I don't know if there's a particular reason for this.

I don't think there is any way to define minimum interchange times more precisely than that, although I know of stations (such as Liverpool Central) where this would make a lot of sense.

 

[alistairlees]

There is a way operators can define a different interchange time based on the operator listed for the service. For Clapham Junction, there's a 5 minute minimum interchange between two Southern services, but 10 if you're using Overground or SWR ones on either leg. I don't know if there's a particular reason for this.

I don't think there is any way to define minimum interchange times more precisely than that, although I know of stations (such as Liverpool Central) where this would make a lot of sense.

Kieron is referring to the TOC-specific interchange (TSI) time. Sometimes this is greater than the general interchange time; sometimes less. The reason for it existing is for the reasons the OP suggests - to introduce more useful interchange times at large stations for certain TOC combinations. The TSI applies to pairs of operators, e.g. Southern to Southern.

There are only about 30 stations that have TSIs. An odd example (at least at first glance) is Wimbledon, where the interchange time from Thameslink to Thameslink is 0 (zero) minutes. I presume this is because there is only one Thameslink platform at Wimbledon, and perhaps also to do with the circular nature of the "Sutton loop" services.

One of the bigger problems (so far as interchange goes) is Kings Cross to St Pancras. As these are separate stations it's impossible to get local connections to be less than 31 minutes (interchange of 15 minutes at each, plus 1 minute walking time) without risking (long-distance) connectivity within each station individually.

 

[alistairlees]

Journey planners aren’t that sophisticated and not should they be as the platform coukdnchange at the last minute. Journey planners also need to account for people who are unfamiliar with the station layout.

If travelling on a walk on ticket there’s absolutely nothing stopping you from catching the earlier train.

Well, they are; or, at least, can be. It's just that the data structure does not support anything more complex. The two (journey planners and data structure) are not the same.

 

[yorkie]

Can the journey planner be sophisticated enough to understand the differences in interchange time between different platforms at the same station?

The short answer is: no.

However you can have differential interchange times within the same TOC, and this does happen at Clapham Junction, as if you are interchanging within GTR Southern it's only 5 minutes.

There is no way for journey planners to give you a shorter interchange time than 10 minutes in your case, even though it's cross platform. Even if someone developed a journey planner that did do that, it would not be compliant with the rules and would not get accredited.

You can view non-valid itineraries at www.fastjp.com; tick 'change at', type CLJ, and choose a layover time of -5, which will be deducted from the usual 10 minute minimum:
http://www.fastjp.com/#journeys?ori...5&odate=20181104&otime=0730&maxres=11&maxch=4

 

[kieron]

An odd example (at least at first glance) is Wimbledon, where the interchange time from Thameslink to Thameslink is 0 (zero) minutes. I presume this is because there is only one Thameslink platform at Wimbledon, and perhaps also to do with the circular nature of the "Sutton loop" services.

They have something similar at Sutton (an 0 minute minimum interchange between two Thameslink trains, or 4 minutes for anything else), and the Sutton loop trains are all shown in the electronic timetable as either starting there or terminating there. There's usually a 2 minute delay between one service finishing and the next starting.

The 0 minute interchange would mean that ticket sites give itineraries which show you staying on the same train, even though the timetable shows them as different services. Except that both Thameslink and Southern run Sutton loop trains, meaning that they may ask you to step back a train anyway.

I think the solution used in Glasgow for the Cathcart loop makes more sense. Trains are shown as running from Glasgow Central to Glasgow Central in the data, which means you (and web sites) only need to consider the minimum interchange time when you are actually changing trains.

 

[zoneking]

After all that, I missed my connection. The Reigate to Victoria arrived at Purley on time (08.24), was delayed into East Croydon, waited some minutes at platform 5, and made an unscheduled stop at Selhurst (which was not recorded on realtime trains).