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