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diff --git a/.idea/gtfs-book/ch-11-stop-transfers.md b/.idea/gtfs-book/ch-11-stop-transfers.md new file mode 100644 index 0000000..6a43674 --- /dev/null +++ b/.idea/gtfs-book/ch-11-stop-transfers.md @@ -0,0 +1,65 @@ +## 11. Stop Transfers (transfers.txt) + +*This file is ***optional*** in a GTFS feed.* + +To define how passengers can transfer between routes at specific stops +feed providers can include `transfers.txt`. This does not mean +passengers cannot transfer elsewhere, but it does indicate if a transfer +is not possible between certain stops, or a minimum time required if +transfer is possible. + +| Field | Required? | Description | +| :----- | :-------- | :---------- | +| `from_stop_id` | Required | The ID of stop as it appears in `stops.txt` where the connection begins. If this references a station, then this rule applies to all stops within the station. | +| `to_stop_id` | Required | The ID of the stop as it appears in `stops.txt` where the connection between trips ends. If this references a station, then this rule applies to all stops within the station. | +| `transfer_type` | Required | `0` or blank means the recommended transfer point, `1` means the secondary vehicle will wait for the first, `2` means a minimum amount of time is required, `3` means transfer is not possible. | +| `min_transfer_time` | Optional | If the `transfer_type` value is `2` then this value must be specified. It indicates the number of seconds required to transfer between the given stops. | + +It is also possible that records in this file are specified for +ticketing reasons. For instance, some train stations are set up so that +passengers can transfer between routes without needing to validate their +ticket again or buy a transfer. Other stations that are shared between +those same routes might not have this open transfer area, thereby +requiring you to exit one route fully before buying another ticket to +access the second. + +### Sample Data + +The following table shows some sample transfer rules from TriMet in +Portland's GTFS feed (<https://openmobilitydata.org/p/trimet>). + +| `from_stop_id` | `to_stop_id` | `transfer_type` | `min_transfer_time` | +| :------------- | :----------- | :-------------- | :------------------ | +| 7807 | 5020 | 0 | | +| 7807 | 7634 | 0 | | +| 7807 | 7640 | 0 | | + +These rules indicate that if you are transferring from a route that +visits stop `7807` to any route that visits the other stops (`5020`, +`7634` or `7640`), then this is the ideal place to do it. + +In other words, if there are other locations along the first route where +you could transfer to the second route, then those stops should not be +used. These rules say this is the best place to transfer. + +Consider the transfer rule in the following table, taken from the New +York City Subway GTFS feed (<https://openmobilitydata.org/p/mta/79>). + +| `from_stop_id` | `to_stop_id` | `transfer_type` | `min_transfer_time` | +| :------------- | :----------- | :-------------- | :------------------ | +| 121 | 121 | 2 | 180 | + +In this data, the MTA specifies how long it takes to transfer to +different platforms within the same station. The stop with ID 121 refers +to the 86th St station (as specified in `stops.txt`). It has a +`location_type` of `1` and two stops within it (`121N` and +`121S`). The above transfer rule says that if you need to transfer +from `121N` to `121S` (or vice-versa) then a minimum time of 3 +minutes (180 seconds) must be allocated. + +If you were to calculate the time taken to transfer using the +coordinates of each of these platforms, it would only take a few seconds +as they are physically close to each other. In reality though, you must +exit one platform then walk around and enter the other platform (often +having to use stairs). + |