Journey planners - where to change?

[Bensonby]

I’m currently travelling from Abbey Wood to Heathrow T5. All of the T5 trains seem to come down from Shenfield, necessitating a change along the way. The first station I could change at is Whitechapel, the last Heathrow T4, with a large number of stations in between. All changes will be on the same platform. All of the journey planners state to change at Farringdon or Paddington.

I’ve also done similar journeys on other routes where there are multiple places you could change.

I was wondering what criteria journey planners apply when determining where to tell people to change? Is there set criteria? What would that criteria be?

 

[Route115?]

I wouldn't change at Heathrow T4! There would be a greater choice of trains at Heathrow T2/3 as the Heathrow Express is free between the stations (4 HEx and two Elizabeth Line per hour). I presume that the route planner would take this into account and that HEx trains are in the system - although in your case maybe not. Other issues are whether you have to change platform & transfer time. That said journey planning algorithms are something of a black box. Its even more complicated when there are differing ticket validities.

 

[Class 170101]

Change at Whitechapel seems to be preferred by TfL as it is the least busy of all the Underground Stations.

Don't go to Terminal 4, you will have to retrace your steps via Heathrow Terminals 2 and 3 to reach Terminal 5.

There are some trains from Shenfield to Terminal 5 (about every 30 minutes).

 

[ctom_s]

If it were me I'd just stay on all the way to Heathrow Central, not only because of the greater choice of trains there as mentioned by Route115? but also because you'll likely have a much better seating situation on your original train than switching onto an already busy service.

But yes on the train they tell you to change at Whitechapel which from everywhere I've seen is because they believe it to be less busy there.

Other constraints would be ease of change (e.g cross platform interchange), and also station capacity. For example Gloucester Road isn't really advertised as a change between District/Piccadilly lines presumably because it's smaller than Earl's Court and South Ken (you may also be reliant on lifts there, but can't remember for sure)