Hidden Assumptions in Journey Planners Tube Routes

I had a look at Gavod’s query on Cycle Journey times from Woodford to Barons Court, and noticed this suggested tube route for the same journey.

I know why it’s telling me to change from the District to the Piccadilly line at Earl’s Court; it’s because the prediction has calculated that I’d be on a Wimbledon train, which doesn’t go to Barons Court. However, most westbound District line trains do go to Barons Court so the chances are that I’d be able to stay on the train on was already on.

I don’t know how you’d do it, but it would be useful to be able to provide this sort of destination information somehow :slight_smile: The assumption that I’m going to end up on a particular service is not really valid.

(…and knowing Earl’s Court quite well, if I had to change, I’d probably just get off and wait for the following District line train, rather that go downstairs to the Piccadilly line).

Hello, thanks for this feedback.

As you’ve probably gathered, Journey Planner works based on routing you using specific services (which I think is how most journey planners work). Although this has an advantage in that we can provide more accurate times, I realise this isn’t necessarily ideal if you only want to get a general idea of a route.

Although this isn’t visible on the website, the destination information is available in the Unified API’s response in the detailed and directions properties of a Leg object (irrelevant properties have been omitted):

    "instruction": {
        "summary": "District line to Earl's Court",
        "detailed": "District line towards Wimbledon",
        "routeOptions": [
                "directions": [
                    "Wimbledon Underground Station"

I suppose the real hidden assumption here is that every leg of the journey is running precisely to time but London is not yet Switzerland! For this journey you get a whole host of options, all of which take within a few minutes of each other. You can of course get rid of the two/three interchanges by specifying minimum number of changes.

You don’t have multiple routeings on buses but for high frequency routes you could get similar apparent slight advantages from changing - but we know that it is the service intervals that are explicitly managed on those routes, not the actual times.

Not sure what you can do about it though!

It’s an interesting challenge, though I should note that our Journey Planner does use live data for bus, Tube, Elizabeth line, London Overground and National Rail services. Even if a service is delayed, that should be reflected in the journey results.

True, @LeonByford, but then you get unknown disruptions to come on top of the known disruptions at the time you make the request (channelling Donald Rumsfeld here…).

It would be nice to see some sort of message along the lines of “other routeings with fewer changes may be almost as quick in practice” but I’d only want to see it when it is genuinely relevant and true and deciding when that is the case is not likely to be simple. Probably not when low frequency services are involved and probably only when the journey times associated with the routeings are very similar.

I’m conscious also that some use JP to find a journey right now while others are looking for general guidance for a journey they want to take at some as yet undecided time in the future.

All in all, probably more of a thought experiment than a practical possibility.

It did occur to me though that it might be helpful to indicate how easy a change is. For example, whether it involves crossing a platform, stairs, lift, escalator or a long walk (like King’s Cross these days). I’d happily make a snap decision to change trains cross-platform but I probably wouldn’t at King’s Cross just for the sake of a possible two minute gain. The interchange times are obviously built in but the hassle factor associated with the change is not, I think, visible. Obviously there is the “full step-free access” option but being fine on necessary steps doesn’t mean you are happy with the fag of any number of steps anywhere. Also a “least walking” option - does that just refer to walking outside the transport system or would it also include walking time within (say) Holborn Station?

Thanks for the reply Leon, and it’s useful to know that train destinations are available from the API if it’s possible to come up with a simple and non-confusing way or incorporating them into the journey suggestion.

I can fully understand why the journey planner uses live data. It’s a simple and generic solution. The more correct instruction:

If your train is to Ealing Broadway or Richmond then stay on it to Barons Court, otherwise get off at Earl’s Court and either wait on the same platform for a District line train towards Ealing Broadway or Richmond, or go downstairs and take any Westbound Piccadilly line train’

…opens up a whole can of worms.

I wonder how long the journey planner allows for the change of line at Earl’s Court?

Perhaps increasing this allowance by two or three minutes would prevent it suggesting the somewhat troublesome transfer unless there were service problems on the District line?