slow-zone
A client & wrapper for CTA 'L' arrival data.
Installation
$ npm install slow-zone
Usage
Make sure you have a CTA Train Tracker API Key.
import SlowZone from "slow-zone";
const client = new SlowZone({ apiKey: "afafafafafafafafafafafafafafafaf" });
Arrivals
getArrivalsForStation(stationId, options?)
Key | Value |
---|---|
stationId |
A CTA station ID. See the CTA API Documentation for valid values. |
options |
(Optional) Additional key/value pairs to pass through to the API. See the CTA API documentation for valid options. |
Returns a Promise that either resolves with an array of objects, each describing a predicted train, or rejects with an error.
// Station: Logan Square
client.getArrivalsForStation(41020)
.then(arrivals => /* do something */)
.catch(err => /* do something */);
getArrivalsForStop(stopId, options?)
Key | Value |
---|---|
stopId |
A CTA stop ID. See the CTA API Documentation for valid values. |
options |
(Optional) Additional key/value pairs to pass through to the API. See the CTA API documentation for valid options. |
Returns a Promise that either resolves with an array of objects, each describing a predicted train, or rejects with an error.
// Stop: Merchandise Mart (Southbound Platform)
// Example uses options to only return Brown Line trains
client.getArrivalsForStop(30091, {rt: "Brn"})
.then(arrivals => /* do something */)
.catch(err => /* do something */);
Follow This Train
followTrain(runId)
Key | Value |
---|---|
runId |
A train run ID. Likely something you got from one of the above API requests. |
Returns a Promise that either resolves with an array of objects, each describing a station stop, or rejects with an error.
sz.followTrain(410)
.then(arrivals => /* do something */)
.catch(err => /* do something */);
Response Structure
Slow Zone reformats and decorates the response from the CTA API to speed up common tasks. Note that all fields may not be present on all responses.
{
"destination": {
"id": 30182,
"name": "Midway"
},
"location": {
"latitude": 41.87685,
"longitude": -87.6327,
"heading": 269
},
"prediction": {
"arrivalMinutes": 1,
"arrivalString": "2:50 p.m.",
"arrivalTime": "2014-10-07T21:50:27.000Z",
"predictionAge": 3531786,
"predictionTime": "2014-10-07T21:49:27.000Z"
},
"route": {
"class": "orange",
"directionId": 5,
"id": "Org",
"name": "Orange",
"run": 715
},
"station": {
"id": 40160,
"name": "LaSalle/Van Buren",
"stop": {
"id": 30031,
"description": "Service at Inner Loop platform"
}
},
"status": {
"approaching": true,
"delayed": false,
"faulty": false,
"scheduled": false
}
}
Destination
Data about the final destination of the predicted train:
Key | Value |
---|---|
destination.id |
(Integer) The GTFS station ID of the final destination station |
destination.name |
(String) The name of the final destination station |
Location
Data about the predicted train's current location:
Key | Value |
---|---|
location.latitude |
(Float) The current latitude of the train |
location.longitude |
(Float) The current longitude of the train |
location.heading |
(Integer) The current heading of the train |
Prediction
The prediction itself, in a number of formats:
Key | Value |
---|---|
prediction.arrivalMinutes |
(Integer) The number of minutes until the train arrives at the station, rounded to the nearest minute |
prediction.arrivalString |
(String) A user-friendly string of the time a train is expected to arrive. Formatted by Dateline |
prediction.arrivalTime |
(Date) The date & time the train is predicted to arrive at the station |
prediction.predictionAge |
(Integer) The number of seconds that have elapsed since the prediction was made |
prediction.predictionTime |
(Date) The date & time when the prediction was generated |
Route
Data about the predicted train's route:
Key | Value |
---|---|
route.class |
(String) The name of the route, lowercased for consistency |
route.directionId |
(Integer) The directionality of the run. See the documentation for specifics, but as a general rule 1 is north & west, 5 is south and east |
route.id |
(String) The CTA ID for the route |
route.name |
(String) The name (color) of the route |
route.run |
(Integer) A unique (that day) identifier for the run |
Station
Data about the station the prediction is relative to:
Key | Value |
---|---|
station.id |
(Integer) The GTFS station ID of the station the prediction is relative to |
station.name |
(String) The name of the station the prediction is relative to |
station.stop.id |
(Integer) The GTFS stop ID of the stop the prediction is relative to |
station.stop.description |
(String) A description of the stop the prediction is relative to. Usually in the format "Service at ___ platform" |
Status
Flags that may affect the reliability or display context of a prediction:
Key | Value |
---|---|
status.approaching |
(Boolean) Indicates that a train is approaching the station |
status.delayed |
(Boolean) Indicates that a train has not reached the next waypoint by the time the prediction expected and it may no longer be accurate |
status.faulty |
(Boolean) Indicates an issue with the train tracker system that prevents a prediction from being made |
status.scheduled |
(Boolean) Indicates that a prediction is based on the preset schedule, not a train in motion. Frequently seen at the start & end of lines |
Development
Command | Description |
---|---|
npm install |
Install dependencies |
npm test |
Run tests |