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CTA Train Tracker API Documentation

Introduction

CTA Train Tracker SM is a product currently in the beta testing phase. This document covers the arrivals API, currently under release for testing and evaluation by developers who work with CTA data.

For complete information about the API and tips, see the main CTA Train Tracker API page.

Note that, to use this API, you must agree to our Developers License Agreement and Terms of Use. You’ll also need to apply for a key.

This documentation is also available as a PDF

 

Table of Contents

 

 

About this document

What this document covers

This document explains how to request information and what information is provided through the single arrivals API. Additional APIs may be released at a later date, and this documentation would then be updated accordingly.

 

What this document does not cover

This document does not cover information provided through the CTA Customer Alerts API, Google Transit Feed Specification data package nor the CTA Bus Tracker API. Go to our Developer Center for more information on these other data services from CTA.

 

How information gets into our system

Information in the CTA Train Tracker beta comes from data fed to CTA from its rail infrastructure (unlike buses, our current railcar fleet does not have GPS hardware). This data is then processed by software we use to monitor our rail system which also generates the predictions for train arrivals based on recent train travel times from one point to another. (The software is a product called QuicTrak®.)

Prediction data are combined with other data and polished to help present information in the most meaningful way possible.

 

Some other things you should know

This service is in beta—it may not always be available and may be changed (see DLA for complete details). Here are some notes about what you can expect from the data:

  • Predictions for train arrivals are generated as trains move from one section of track to another and for estimated arrivals up to fifteen minutes beyond the train’s current position.
     
  • Predictions may be withheld in circumstances where we expect them to be inaccurate, such as during major work, reroutes or unavoidable service disruptions.

    Important tip: Use the Customer Alerts API to determine whether or not an event is affecting service and relay to your end-users when some or all predictions may be affected or unavailable due to an event that affects service.
     
  • When no predictions are available for a station, such as because no train has yet departed a terminal, we offer up to one scheduled departure time in place of a live prediction so long as service is scheduled. Terminal departures are always represented as a scheduled departure, as live information is not presently available until a train leaves.
     
  • Arrival predictions are available for locations where trains pick up passengers (predictions for terminal arrivals and exit-only platforms are not presently available in the data).
     
  • Predictions for a specific train run number are not available at this time—only for arrival/departures from stops where passengers are accepted.
     
  • Internal testing has shown train arrival accuracy averages <±1 minute from prediction times. Average actual variance from predictions may vary as traffic conditions change.
     
  • Unscheduled express runs (where a train runs non-stop from one point on a route to another, such as to space out service following an unavoidable delay) are not expressed in CTA Train Tracker at this time.
     
  • The default daily transaction limit for this API is 50,000 transactions. If you need additional transactions, contact webmaster@transitchicago.com with your request. Additionally, there is DoS protection installed on our servers which may trigger a temporary “time-out” if a large number of transactions from a single IP address.

 

 

Why we’re providing this API

The hope is that, by publishing this data, it ends up in all sorts of places beyond CTA’s sites and services. By having transit information in as many contexts as people might use it, we can extend our reach and help people make informed decisions which can improve people’s experiences with transit.

If you experience any issues or have any comments regarding this service and related policies, please contact us right away. Your feedback is extremely valuable to us!

 

Legal notice

By using this API, you agree to our Developer License Agreement and Terms of Use, the latest version of which is included, as of the publication date of this document, in this document’s appendices.

It’s important that you, the developer, understand that this service is provided on an as-is basis and without any guarantees as to availability or accuracy. You must read and agree to the full Developer Terms of Use to use this API.

 
 

A few definitions…

There are a few bits of lingo that you’ll find in this document (we’ll try to keep it to a minimum) that we’d like to explain first, so you know what we’re talking about.

  • Customer Alert – An entry in our Customer Alerts database which describes a condition that can affect someone’s trip on CTA; see Customer Alerts API for comprehensive alert information, including a special flag for train alerts that indicates whether or not an event may cause Train Tracker to behave less-reliably than normal.
     
  • Google Transit Feed Specification (GTFS) – This is a “common format for public transportation schedules and associated geographic information.” GTFS is used by hundreds of transit agencies to feed service information to Google™. A GTFS package is generated, as needed, by transit agencies and can be distributed as a simple .zip file with several comma-delimited text files inside. You can read more about GTFS on Google Code. For consistency, the same route IDs and stop IDs are used throughout the Bus Tracker system, the Alerts system as are specified in the CTA GTFS feed (with a few special exceptions—see appendix).
     
  • Delay – In the context of this document, a delayed train is one that has not moved from one track circuit to another for an abnormally long period of time.
     
  • Terminal – A point of departure or terminus on a train route.


 

Train location data coming soon

We’re working on releasing an API into train location data (like what powers our beta map).

We understand that this is an exciting new feature lots of you have been waiting for, but we just need a little time to finish the development on the API bits. We're sorry we don't have this yet, but we appreciate your patience while we put together something that'll be stable and supported.

 

Arrivals API

Description

This API produces a list of arrival predictions for all platforms at a given train station in a well-formed XML document. Registration and receipt of an API key is required for use of this API.

Each separate prediction describes a single train, when it’s expected to arrive, and various bits of information that explain where it’s expected to arrive and certain attributes about the train.

 

Base URL

http://lapi.transitchicago.com/api/1.0/ttarrivals.aspx

 

Parameters

Use URL query string method.

Name

Value

Description

mapid

Numeric station identifier (required if stpid not specified)

A single five-digit code to tell the server which station you’d like to receive predictions for. See appendix for information about valid station codes.

stpid

Numeric stop identifier
(required if mapid not specified)

A single five-digit code to tell the server which specific stop (in this context, specific platform or platform side within a larger station) you’d like to receive predictions for. See appendix for information about valid stop codes.

max

Maximum results (optional)

The maximum number you’d like to receive (if not specified, all available results for the requested stop or station will be returned)

rt

Route code (optional)

Allows you to specify a single route for which you’d like results (if not specified, all available results for the requested stop or station will be returned)

key

Alphanumeric API key
(required)

Your unique API key, assigned to you after agreeing to DLA and requesting a key be generated for you.

 

 

Response fields:

Name

Description

ctatt

Root element

./tmst

Shows time when response was generated in format:
yyyyMMdd HH:mm:ss (24-hour format, time local to Chicago)

./errCd

Numeric error code (see appendices)

./errNm

Textual error description/message (see appendices)

./eta

Container element (one per individual prediction)

././staId

Numeric GTFS parent station ID which this prediction is for (five digits in 4xxxx range) (matches “mapid” specified by requestor in query)

././stpId

Numeric GTFS unique stop ID within station which this prediction is for (five digits in 3xxxx range)

././staNm

Textual proper name of parent station

././stpDe

Textual description of platform for which this prediction applies

././rn

Run number of train being predicted for

././rt

Textual, abbreviated route name of train being predicted for (matches GTFS routes)

././destSt

GTFS unique stop ID where this train is expected to ultimately end its service run (experimental and supplemental only—see note below)

././destNm

Friendly destination description (see note below)

././trDr

Numeric train route direction code (see appendices)

././prdt

Date-time format stamp for when the prediction was generated:
yyyyMMdd HH:mm:ss (24-hour format, time local to Chicago)

././arrT

Date-time format stamp for when a train is expected to arrive/depart:
yyyyMMdd HH:mm:ss (24-hour format, time local to Chicago)

././isApp

Indicates that Train Tracker is now declaring “Approaching” or “Due” on site for this train

././isSch

Boolean flag to indicate whether this is a live prediction or based on schedule in lieu of live data

././isFlt

Boolean flag to indicate whether a potential fault has been detected (see note below)

././isDly

Boolean flag to indicate whether a train is considered “delayed” in Train Tracker

././flags Train flags (not presently in use)
././lat Latitude position of the train in decimal degrees
././lon Longitude position of the train in decimal degrees
././heading Heading, expressed in standard bearing degrees (0 = North, 90 = East, 180 = South, and 270 = West; range is 0 to 359, progressing clockwise)

 

Sample Request URL:

http://lapi.transitchicago.com/api/1.0/ttarrivals.aspx?key=a8456dcbhf8475683cf7818bca81&mapid=40380&max=5  

 

Remarks:

Stop IDs:
Use stop information in GTFS Stops table for associated geolocation of stops listed here. For purposes of this API, use the parent station ID (4xxxx range of stop ID numbers) to specify a station.

Destination station ID #s:
IDs in destSt refer to the ultimate destination of a train per the information about each train that’s on the move.

These destination station ID #s are only available once a train has departed (on schedule-based predictions, this element will show “0”) and doesn’t necessarily match with what will be indicated on a train’s destination sign (particularly on routes that operate around the whole Loop).

Once a train leaves Midway, its ultimate destination station’s ID is “Midway” because the train will make all stops to the Loop, go around it, and come back to Midway. This allows you to write your own logic on what to show, but we’ve already gone and done the work for you.

The destNm element is the public, friendly-name that should match the destination sign of approaching trains. For example, predictions a train heading toward the Loop on the Orange Line, using this element, will return “Loop” in a result set at Roosevelt, but that same train, even while still Loop-bound, will be listed as being to “Midway” for Harold Washington Library/State-Van Buren, because our system knows that once it gets to Library, it’ll now be considered a Midway-bound train.

Lat/lon/heading: This information is available only for trains that are in-service (i.e., have left their terminals). Some entries are based on our written schedule, as a courtesy, for when live information isn’t available. Schedule-based entries in a response will simply have an empty lat, lon and heading element as location info isn’t available.

Calculating a number of minutes: See Appendix D for extended notes on this subject.

 


 

XML Schema

<?xml version="1.0" encoding="utf-8"?>
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
 <xs:element name="ctatt">
   <xs:complexType>
     <xs:sequence>
       <xs:element name="tmst" type="xs:string" />
       <xs:element name="errCd" type="xs:unsignedByte" />
       <xs:element name="errNm" />
       <xs:element maxOccurs="unbounded" name="eta">
         <xs:complexType>
           <xs:sequence>
             <xs:element name="staId" type="xs:unsignedShort" />
             <xs:element name="stpId" type="xs:unsignedShort" />
             <xs:element name="staNm" type="xs:string" />
             <xs:element name="stpDe" type="xs:string" />
             <xs:element name="rn" type="xs:unsignedShort" />
             <xs:element name="rt" type="xs:string" />
             <xs:element name="destSt" type="xs:unsignedShort" />
             <xs:element name="destNm" type="xs:string" />
             <xs:element name="trDr" type="xs:unsignedByte" />
             <xs:element name="prdt" type="xs:string" />
             <xs:element name="arrT" type="xs:string" />
             <xs:element name="isApp" type="xs:unsignedByte" />
             <xs:element name="isSch" type="xs:unsignedByte" />
             <xs:element name="isDly" type="xs:unsignedByte" />
             <xs:element name="isFlt" type="xs:unsignedByte" />
             <xs:element name="flags" type="xs:string" />
             <xs:element name="lat" type="xs:decimal" />
             <xs:element name="lon" type="xs:decimal" />
             <xs:element name="heading" type="xs:unsignedShort" />
           </xs:sequence>
         </xs:complexType>
       </xs:element>
     </xs:sequence>
   </xs:complexType>
 </xs:element>
</xs:schema>

 

Example

Request:
http://lapi.transitchicago.com/api/1.0/ttarrivals.aspx?key=a8456dcbhf8475683cf7818bca81&max=1&mapid=40360

What this request is asking for:
A maximum of one arrival prediction result from the station with the ID #40360. It also passes the API key for authorization (required).

 

Response:

<?xml version="1.0" encoding="UTF-8"?>
<ctatt>

  <tmst>20110618 23:26:50</tmst>
  <errCd>
0</errCd>
  <errNm/>
  <eta>
    <staId>
40360</staId>
    <stpId>
30070</stpId>
    <staNm>
Southport</staNm>
    <stpDe>
Service toward Kimball</stpDe>
    <rn>
419</rn>
    <rt>
Brn</rt>
    <destSt>
30249</destSt>
    <destNm>
Kimball</destNm>
    <trDr>
1</trDr>
    <prdt>
20110618 23:26:12</prdt>
    <arrT>
20110618 23:28:12</arrT>
    <isApp>
0</isApp>
    <isSch>
0</isSch>
    <isDly>
0</isDly>
    <isFlt>
0</isFlt>
    <flags/>
  
  <lat>41.97776</lat>
   
<lon>-87.77567</lon>
    <heading>
299</heading>
  </eta>
</ctatt>

 

 

Follow This Train API

Description

This API produces a list of arrival predictions for a given train at all subsequent stations for which that train is estimated to arrive, up to 20 minutes in the future or to the end of its trip.

Each separate prediction describes a single train, when it’s expected to arrive, and various bits of information that explain where it’s expected to arrive and certain attributes about the train.

Base URL

lapi.transitchicago.com/api/1.0/ttfollow.aspx

Parameters

Use URL query string method.

 

Name
Value
Description
runnumber
Train Run Number (required)
Allows you to specify a single run number for a train for which you’d like a series of upcoming arrival estimations.
key
Alphanumeric API key
(required)
Your unique API key, assigned to you after agreeing to DLA and requesting a key be generated for you.

 
 
Response fields:

Name
Description
ctatt
Root element
./tmst
Shows time when response was generated in format:
yyyyMMdd HH:mm:ss (24-hour format, time local to Chicago)
./errCd
Numeric error code (see appendices)
./errNm
Textual error description/message (see appendices)
./position Container element (one per response describing train)
././lat Latitude position of the train in decimal degrees
././lon Longitude position of the train in decimal degrees
././heading Heading, expressed in standard bearing degrees (0 = North, 90 = East, 180 = South, and 270 = West; range is 0 to 359, progressing clockwise)
./eta
Container element (one per individual prediction)
././staId
Numeric GTFS parent station ID which this prediction is for (five digits in 4xxxx range) (matches “mapid” specified by requestor in query)
././stpId
Numeric GTFS unique stop ID within station which this prediction is for (five digits in 3xxxx range)
././staNm
Textual proper name of parent station
././stpDe
Textual description of platform for which this prediction applies
././rn
Run number of train being predicted for
././rt
Textual, abbreviated route name of train being predicted for (matches GTFS routes)
././destSt
GTFS unique stop ID where this train is expected to ultimately end its service run (experimental and supplemental only—see note below)
././destNm
Friendly destination description (see note below)
././trDr
Numeric train route direction code (see appendices)
././prdt
Date-time format stamp for when the prediction was generated:
yyyyMMdd HH:mm:ss (24-hour format, time local to Chicago)
././arrT
Date-time format stamp for when a train is expected to arrive/depart:
yyyyMMdd HH:mm:ss (24-hour format, time local to Chicago)
././isApp
Indicates that Train Tracker is now declaring “Approaching” or “Due” on site for this train
././isSch
Boolean flag to indicate whether this is a live prediction or based on schedule in lieu of live data
././isFlt
Boolean flag to indicate whether a potential fault has been detected (see note below)
././isDly
Boolean flag to indicate whether a train is considered “delayed” in Train Tracker
././flags Train flags (not presently in use)

 
Sample Request URL:
 
Remarks:

Stop IDs: Use stop information in GTFS Stops table for associated geolocation of stops listed here. For purposes of this API, use the parent station ID (4xxxx range of stop ID numbers) to specify a station.

Destination station ID #s: in destSt refer to the ultimate destination of a train per the information about each train that’s on the move.

These destination station ID #s are only available once a train has departed (on schedule-based predictions, this element will show “0”) and doesn’t necessarily match with what will be indicated on a train’s destination sign (particularly on routes that operate around the whole Loop).

Once a train leaves Midway, its ultimate destination station’s ID is “Midway” because the train will make all stops to the Loop, go around it, and come back to Midway. This allows you to write your own logic on what to show, but we’ve already gone and done the work for you.

The destNm element is the public, friendly-name that should match the destination sign of approaching trains. For example, predictions a train heading toward the Loop on the Orange Line, using this element, will return “Loop” in a result set at Roosevelt, but that same train, even while still Loop-bound, will be listed as being to “Midway” for Harold Washington Library/State-Van Buren, because our system knows that once it gets to Library, it’ll now be considered a Midway-bound train.

Calculating a number of minutes: See Appendix D for extended notes on this subject.

 

XML Schema

<?xml version="1.0" encoding="utf-8"?>
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
    <xs:element name="ctatt">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="tmst" type="xs:string" />
                <xs:element name="errCd" type="xs:unsignedByte" />
                <xs:element name="errNm" />
                <xs:element name="position" />
                    <xs:complexType>
                        <xs:sequence>
                               <xs:element name="lat" type="xs:decimal" />
                               <xs:element name="lon" type="xs:decimal" />
                               <xs:element name="heading" type="xs:unsignedShort" />
                        </xs:sequence>
                    </xs:complexType>
                </xs:element>
                <xs:element maxOccurs="unbounded" name="eta">
                    <xs:complexType>
                        <xs:sequence>
                            <xs:element name="staId" type="xs:unsignedShort" />
                            <xs:element name="stpId" type="xs:unsignedShort" />
                            <xs:element name="staNm" type="xs:string" />
                            <xs:element name="stpDe" type="xs:string" />
                            <xs:element name="rn" type="xs:unsignedByte" />
                            <xs:element name="rt" type="xs:string" />
                            <xs:element name="destSt" type="xs:unsignedShort" />
                            <xs:element name="destNm" type="xs:string" />
                            <xs:element name="trDr" type="xs:unsignedByte" />
                            <xs:element name="prdt" type="xs:string" />
                            <xs:element name="arrT" type="xs:string" />
                            <xs:element name="isApp" type="xs:unsignedByte" />
                            <xs:element name="isSch" type="xs:unsignedByte" />
                            <xs:element name="isDly" type="xs:unsignedByte" />
                            <xs:element name="isFlt" type="xs:unsignedByte" />
                            <xs:element name="flags" type="xs:string" />
                            <xs:element name="lat" type="xs:decimal" />
                            <xs:element name="lon" type="xs:decimal" />
                            <xs:element name="heading" type="xs:unsignedShort" />
                        </xs:sequence>
                    </xs:complexType>
                </xs:element>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
</xs:schema>
 
 

Example

Request:
http://lapi.transitchicago.com/api/1.0/ttarrivals.aspx?key=e3875818a474304&runnumber=12

What this request is asking for:
Upcoming arrivals for run 123 (a Blue Line train). It also passes the API key for authorization (required).

(For brevity, what would be a longer series of “eta” sequence element is limited to two in this example.)
 
Response:
 

<?xml version="1.0" encoding="utf-8" ?>
<ctatt>
  <tmst>20130515 14:11:17</tmst>
  <errCd>0</errCd> 
  <errNm />
  <position>
    <lat>
41.97776</lat>
    <lon>
-87.77567</lon>
    <heading>
299</heading>
  </position>

  <eta>
    <staId>40010</staId>
    <stpId>30001</stpId>
    <staNm>Austin</staNm>
    <stpDe>Austin to O'Hare</stpDe>
    <rn>123</rn>
    <rt>Blue Line</rt>
    <destSt>30171</destSt>
    <destNm>O'Hare</destNm>
    <trDr>1</trDr>
    <prdt>20130515 14:10:23</prdt>
    <arrT>20130515 14:11:23</arrT>
    <isApp>1</isApp>
    <isSch>0</isSch>
    <isDly>0</isDly>
    <isFlt>0</isFlt>
    <flags/> 
  </eta>
  <eta>
    <staId>40970</staId>
    <stpId>30187</stpId>
    <staNm>Cicero</staNm>
    <stpDe>Cicero to O'Hare</stpDe>
    <rn>123</rn>
    <rt>Blue Line</rt>
    <destSt>30171</destSt>
    <destNm>O'Hare</destNm>
    <trDr>1</trDr>
    <prdt>20130515 14:10:23</prdt>
    <arrT>20130515 14:15:23</arrT>
    <isApp>0</isApp>
    <isSch>0</isSch>
    <isDly>0</isDly>
    <isFlt>0</isFlt>
    <flags/> 
  </eta>
</ctatt>


 

Locations API

Description

This API produces a list of in-service trains and basic info and their locations for one or more specified ‘L’ routes.

Each separate entry describes a single train and provides coordinate, geospatial heading, certain train attributes and next stop information.

Base URL

lapi.transitchicago.com/api/1.0/ttpositions.aspx

Parameters:
Use URL query string method.

 

Name
Value
Description
rt
Train route(s) (required)
Allows you to specify one or more routes for which you’d like train location information.
key
Alphanumeric API key
(required)
Your unique API key, assigned to you after agreeing to DLA and requesting a key be generated for you.

 
 
Response fields:

Name
Description
ctatt
Root element
./tmst
Shows time when response was generated in format:
yyyyMMdd HH:mm:ss (24-hour format, time local to Chicago)
./errCd
Numeric error code (see appendices)
./errNm
Textual error description/message (see appendices)
./route name=
Container element (one per route in response), name attribute indicates route per GTFS-matching route identifiers (see appendices)
././train
Container element (one per train in response)
./././rn
Run number
./././destSt
GTFS unique stop ID where this train is expected to ultimately end its service run (experimental and supplemental only—see note below)
./././destNm
Friendly destination description (see note below)
./././trDr
Numeric train route direction code (see appendices)
./././nextStaId
Next station ID (parent station ID matching GTFS)
./././nextStpId
Next stop ID (stop ID matching GTFS)
./././nextStaNm
Proper name of next station
./././prdt
Date-time format stamp for when the prediction was generated:
yyyyMMdd HH:mm:ss (24-hour format, time local to Chicago)
./././arrT
Date-time format stamp for when a train is expected to arrive/depart:
yyyyMMdd HH:mm:ss (24-hour format, time local to Chicago)
./././isApp
Indicates that Train Tracker is now declaring “Approaching” or “Due” on site for this train
./././isDly
Boolean flag to indicate whether a train is considered “delayed” in Train Tracker
./././flags
Train flags (not presently in use)
./././lat
Latitude position of the train in decimal degrees
./././lon
Longitude position of the train in decimal degrees
./././heading
Heading, expressed in standard bearing degrees (0 = North, 90 = East, 180 = South, and 270 = West; range is 0 to 359, progressing clockwise)

 
 

XML Schema

<?xml version="1.0" encoding="utf-8"?>
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
    <xs:element name="ctatt">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="tmst" type="xs:string" />
                <xs:element name="errCd" type="xs:unsignedByte" />
                <xs:element name="errNm" />
                <xs:element maxOccurs="unbounded" name="route">
                    <xs:complexType>
                        <xs:sequence>
                            <xs:element maxOccurs="unbounded" name="train">
                                <xs:complexType>
                                    <xs:sequence>
                                        <xs:element name="rn" type="xs:unsignedShort" />
                                        <xs:element name="destSt" type="xs:unsignedShort" />
                                        <xs:element name="destNm" type="xs:string" />
                                        <xs:element name="trDr" type="xs:unsignedByte" />
                                        <xs:element name="nextStaId" type="xs:unsignedShort" />
                                        <xs:element name="nextStpId" type="xs:unsignedShort" />
                                        <xs:element name="nextStaNm" type="xs:string" />
                                        <xs:element name="prdt" type="xs:string" />
                                        <xs:element name="arrT" type="xs:string" />
                                        <xs:element name="isApp" type="xs:unsignedByte" />
                                        <xs:element name="isDly" type="xs:unsignedByte" />
                                        <xs:element name="flags" type="xs:string" />
                                        <xs:element name="lat" type="xs:decimal" />
                                        <xs:element name="lon" type="xs:decimal" />
                                        <xs:element name="heading" type="xs:unsignedShort" />
                                    </xs:sequence>
                                </xs:complexType>
                            </xs:element>
                        </xs:sequence>
                        <xs:attribute name="name" type="xs:string" use="required" />
                    </xs:complexType>
                </xs:element>
            </xs:sequence>
 
       </xs:complexType>
    </xs:element>
</xs:schema>

 

Example:

 
Response:
<?xml version="1.0" encoding="utf-8" ?>
<ctatt>
 <tmst>20130610 15:00:21</tmst>
 <errCd>0</errCd>
 <errNm />
 <route name="red">
    <train>
      <rn>804</rn>
      <destSt>30173</destSt>
      <destNm>Howard</destNm>
      <trDr>1</trDr>
      <nextStaId>41400</nextStaId>
      <nextStpId>30269</nextStpId>
      <nextStaNm>Roosevelt</nextStaNm>
      <prdt>20130610 14:58:48</prdt>
      <arrT>20130610 14:59:48</arrT>
      <isApp>1</isApp>
      <isDly>0</isDly>
      <flags />
      <lat>41.86579</lat>
      <lon>-87.62736</lon>
      <heading>358</heading>
    </train>
    <train>
      <rn>808</rn>
      <destSt>30173</destSt>
      <destNm>Howard</destNm>
      <trDr>1</trDr>
      <nextStaId>40510</nextStaId>
      <nextStpId>30099</nextStpId>
      <nextStaNm>Garfield</nextStaNm>
      <prdt>20130610 14:58:03</prdt>
      <arrT>20130610 15:00:03</arrT>
      <isApp>0</isApp>
      <isDly>0</isDly>
      <flags />
      <lat>41.78697</lat>
      <lon>-87.6187</lon>
      <heading>81</heading>
    </train>
  </route>
</ctatt>

 

Appendices

 

Appendix A: Route ID Quick Reference

CTA ‘L’

‘L’ routes (rapid transit train services) are identified as follows:

  • Red = Red Line (Howard-95th/Dan Ryan service)
  • Blue = Blue Line (O’Hare-Forest Park service)
  • Brn = Brown Line (Kimball-Loop service)
  • G = Green Line (Harlem/Lake-Ashland/63rd-Cottage Grove service)
  • Org = Orange Line (Midway-Loop service)
  • P = Purple Line (Linden-Howard shuttle service)
  • Pink = Pink Line (54th/Cermak-Loop service)
  • Y = Yellow Line (Skokie-Howard [Skokie Swift] shuttle service)

 

Note: In the separate Customer Alerts API, alerts that apply specifically to the Purple Line Express (but not Purple Line Local/Shuttle service north of Howard) will use the additional route designator “Pexp”. When integrating Customer Alert information into your code project, be sure to account that alerts applying to the Purple Line may have either route designator “P” or “Pexp” (or both).

 


 

Appendix B: Station IDs

Each bus or train stop on the CTA system, as you’ll see if you look at the “stops” table in our Google Transit Feed Specification feed, has its own unique identifier. This helps to power trip planners such as the Google Maps transit directions capability in identifying individual locations and paths where vehicles make stops along a route in each direction.
 

Note, however, that in the GTFS data, most train stations have three entries in the stops table—one in each direction, with a third entry that covers the entire station facility, known as the “parent stop.” We’ve numbered our stops differently, using the following convention:

0-29999                  = Bus stops
30000-39999          = Train stops
40000-49999          = Train stations (parent stops)

The API accepts and responds with both train stop IDs and station IDs to allow you maximum flexibility in how you build your application.

 

More help
A complete list of CTA 'L' stops is also available from the City of Chicago's Data Portal, which offers API's to download these lists in machine-readable formats.
 

 

 

Example from GTFS

For example, Southport, on the Brown Line has three entries in our GTFS table (only relevant rows shown here):

stop_id,stop_code,stop_name,stop_lat,stop_lon,location_type,parent_station,wheelchair_boarding
30070,,"Southport",41.943744,-87.663619,0,40360,1
30071,,"Southport",41.943744,-87.663619,0,40360,1
40360,,"Southport",41.943744,-87.663619,1,,1 

The first two represent specific stops in GTFS—one for each direction from the Southport station (toward Loop or toward Kimball).

The third entry is the associated parent station GTFS, which represents the entire station facility known as “Southport” inside of which these separate “stops” are grouped.

Note that while Southport’s parent entry and individual stop entries all have the same basic attributes, this may vary in some stations for map clarity and to assist trip planners (particularly where bus stops also reference a parent station at a larger transfer facility like the transit center at Jefferson Park).

 

How these look in the API

In the Arrivals API, for example, responses for Southport might include either:

<staId>40360</staId>
<stpId>30071</stpId>
<staNm>Southport</staNm>
<stpDe>Service toward Loop</stpDe>

Or

<staId>40360</staId>
<stpId>30070</stpId>
<staNm>Southport</staNm>
<stpDe>Service toward Kimball</stpDe>

This allows you to reference GTFS for a variety of things, and also provides you additional descriptive information which helps you explain results to your customers, depending on how you wish to present them.

 

Parent Stop ID Quick Reference

This is a list of the parent stops and their associated ID# in GTFS.

A complete list of CTA 'L' stops is also available from the City of Chicago's Data Portal, which offers API's to download these lists in machine-readable formats.


 

Descriptive station name

StopID

18th 40830
35th-Bronzeville-IIT 41120
35th/Archer 40120
43rd 41270
47th (Green Line) 41080
47th (Red Line) 41230
51st 40130
54th/Cermak 40580
63rd 40910
69th 40990
79th 40240
87th 41430
95th 40450
Adams/Wabash 40680
Addison (Blue Line) 41240
Addison (Brown Line) 41440
Addison (Red Line) 41420
Argyle 41200
Armitage 40660
Ashland/63rd 40290
Ashland (Green, Pink Lines) 40170
Ashland (Orange Line) 41060
Austin (Blue Line) 40010
Austin (Green Line) 41260
Belmont (Red, Brown, Purple Lines) 41320
Belmont (Blue Line) 40060
Berwyn 40340
Bryn Mawr 41380
California (Pink Line) 40440
California (Green Line) 41360
California (Blue Line-O'Hare Branch) 40570
Central Park 40780
Central (Green Line) 40280
Central (Purple Line) 41250
Cermak-Chinatown 41000
Cermak-McCormick Place 41690
Chicago (Blue Line) 41410
Chicago (Brown Line) 40710
Chicago (Red Line) 41450
Cicero (Pink Line) 40420
Cicero (Blue Line-Forest Park Branch) 40970
Cicero (Green Line) 40480
Clark/Division 40630
Clark/Lake 40380
Clinton (Blue Line) 40430
Clinton (Green Line) 41160
Conservatory 41670
Cumberland 40230
Damen (Brown Line) 40090
Damen (Pink Line) 40210
Damen (Blue Line-O'Hare Branch) 40590
Davis 40050
Dempster 40690
Dempster-Skokie 40140
Diversey 40530
Division 40320
Cottage Grove 40720
Forest Park 40390
Foster 40520
Francisco 40870
Fullerton 41220
Garfield (Green Line) 40510
Garfield (Red Line) 41170
Grand (Blue Line) 40490
Grand (Red Line) 40330
Granville 40760
Halsted (Green Line) 40940
Halsted (Orange Line) 41130
Harlem (Blue Line-Forest Park Branch) 40980
Harlem (Green Line) 40020
Harlem (Blue Line-O'Hare Branch) 40750
Harold Washington Library-State/Van Buren 40850
Harrison 41490
Howard 40900
Illinois Medical District 40810
Indiana 40300
Irving Park (Blue Line) 40550
Irving Park (Brown Line) 41460
Jackson (Blue Line) 40070
Jackson (Red Line) 40560
Jarvis 41190
Jefferson Park 41280
Kedzie (Brown Line) 41180
Kedzie (Pink Line) 41040
Kedzie (Green Line) 41070
Kedzie-Homan (Blue Line) 40250
Kedzie (Orange Line) 41150
Kimball 41290
King Drive 41140
Kostner 40600
Lake 41660
Laramie 40700
LaSalle 41340
LaSalle/Van Buren 40160
Lawrence 40770
Linden 41050
Logan Square 41020
Loyola 41300
Main 40270
Midway 40930
Monroe (Blue Line) 40790
Monroe (Red Line) 41090
Montrose (Blue Line) 41330
Montrose (Brown Line) 41500
Morgan 41510
Morse 40100
North/Clybourn 40650
Noyes 40400
Oak Park (Blue Line) 40180
Oak Park (Green Line) 41350
Oakton-Skokie 41680
O'Hare 40890
Paulina 41310
Polk 41030
Pulaski (Pink Line) 40150
Pulaski (Blue Line-Forest Park Branch) 40920
Pulaski (Green Line) 40030
Pulaski (Orange Line) 40960
Quincy/Wells 40040
Racine 40470
Randolph/Wabash 40200
Ridgeland 40610
Rockwell 41010
Roosevelt 41400
Rosemont 40820
Sedgwick 40800
Sheridan 40080
South Boulevard 40840
Southport 40360
Sox-35th 40190
State/Lake 40260
Thorndale 40880
UIC-Halsted 40350
Washington/Wells 40730
Washington (Blue Line) 40370
Wellington 41210
Western (Brown Line) 41480
Western (Pink Line) 40740
Western (Blue Line-Forest Park Branch) 40220
Western (Blue Line-O'Hare Branch) 40670
Western (Orange Line) 40310
Wilson 40540

 

 

Individual Stop IDs Quick Reference

This is a list of the parent stops and their associated ID# in GTFS.

A complete list of CTA 'L' stops is also available from the City of Chicago's Data Portal, which offers API's to download these lists in machine-readable formats.

 

Stop_ID

Descriptive Stop Name

Normal traffic flow to:

Parent Stop_ID

30162

18th West 40830
30161 18th East 40830
30214 35-Bronzeville-IIT South 41120
30213 35-Bronzeville-IIT North 41120
30023 35th/Archer South 40120
30022 35th/Archer North 40120
30246 43rd South 41270
30245 43rd North 41270
30209 47th (Green Line) North 41080
30210 47th (Green Line) South 41080
30237 47th (Red Line) North 41230
30238 47th (Red Line) South 41230
30024 51st North 40130
30025 51st South 40130
30114 54th/Cermak West 40580
30113 54th/Cermak East 40580
30177 63rd North 40910
30178 63rd South 40910
30192 69th South 40990
30191 69th North 40990
30046 79th North 40240
30047 79th South 40240
30276 87th South 41430
30275 87th North 41430
30088 95th North 40450
30089 95th South 40450
30131 Adams/Wabash North (Outer Loop) 40680
30132 Adams/Wabash South (Inner Loop) 40680
30240 Addison (Blue Line) South 41240
30239 Addison (Blue Line) North 41240
30278 Addison (Brown Line) South 41440
30277 Addison (Brown Line) North 41440
30273 Addison (Red Line) North 41420
30274 Addison (Red Line) South 41420
30230 Argyle South 41200
30229 Argyle North 41200
30127 Armitage North 40660
30128 Armitage South 40660
30056 Ashland/63rd East 40290
30057 Ashland/63rd West 40290
30032 Ashland (Green, Pink Lines) West 40170
30033 Ashland (Green, Pink Lines) East 40170
30205 Ashland (Orange Line) North 41060
30206 Ashland (Orange Line) South 41060
30001 Austin (Blue Line) East 40010
30002 Austin (Blue Line) West 40010
30243 Austin (Green Line) East 41260
30244 Austin (Green Line) West 41260
30255 Belmont North 41320
30256 Belmont South 41320
30257 Belmont North 41320
30258 Belmont South 41320
30013 Belmont (Blue Line) South 40060
30012 Belmont (Blue Line) North 40060
30067 Berwyn South 40340
30066 Berwyn North 40340
30267 Bryn Mawr North 41380
30268 Bryn Mawr South 41380
30087 California (Pink Line) West 40440
30086 California (Pink Line) East 40440
30266 California (Green Line) West 41360
30265 California (Green Line) East 41360
30111 California (Blue Line-O'Hare Branch) North 40570
30112 California (Blue Line-O'Hare Branch) South 40570
30151 Central Park East 40780
30152 Central Park West 40780
30054 Central (Green Line) East 40280
30055 Central (Green Line) West 40280
30241 Central-Purple North 41250
30242 Central-Purple South 41250
30194 Cermak-Chinatown South 41000
30193 Cermak-Chinatown North 41000
30381 Cermak-McCormick Place North 41690
30382 Cermak-McCormick Place South 41690
30271 Chicago (Blue Line) North 41410
30272 Chicago (Blue Line) South 41410
30137 Chicago (Brown Line) North 40710
30138 Chicago (Brown Line) South 40710
30280 Chicago (Red Line) South 41450
30279 Chicago (Red Line) North 41450
30082 Cicero (Pink Line) East 40420
30083 Cicero (Pink Line) West 40420
30188 Cicero-Forest Park West 40970
30187 Cicero-Forest Park East 40970
30009 Cicero (Green Line) West 40480
30094 Cicero (Green Line) East 40480
30122 Clark/Division South 40630
30121 Clark/Division North 40630
30074 Clark/Lake (Elevated) East (Inner Loop) 40380
30075 Clark/Lake (Elevated) West (Outer Loop) 40380
30375 Clark/Lake (Subway) North 40380
30374 Clark/Lake (Subway) South 40380
30084 Clinton (Blue Line) East 40430
30085 Clinton (Blue Line) West 40430
30221 Clinton (Green, Pink Lines) East 41160
30222 Clinton (Green, Lines) West 41160
30291 Conservatory East 41670
30292 Conservatory West 41670
30045 Cumberland South 40230
30044 Cumberland North 40230
30018 Damen (Brown Line) North 40090
30019 Damen (Brown Line) South 40090
30040 Damen (Pink Line) East 40210
30041 Damen (Pink Line) West 40210
30116 Damen (Blue Line-O'Hare Branch) South 40590
30115 Damen (Blue Line-O'Hare Branch) North 40590
30010 Davis North 40050
30011 Davis South 40050
30134 Dempster South 40690
30133 Dempster North 40690
30026 Dempster-Skokie North 40140
30027 Dempster-Skokie South 40140
30103 Diversey North 40530
30104 Diversey South 40530
30062 Division North 40320
30063 Division South 40320
30139 Cottage Grove East 40720
30140 Cottage Grove West 40720
30077 Forest Park West 40390
30076 Forest Park East 40390
30101 Foster North 40520
30102 Foster South 40520
30168 Francisco South 40870
30167 Francisco North 40870
30233 Fullerton North 41220
30236 Fullerton South 41220
30235 Fullerton North 41220
30234 Fullerton South 41220
30099 Garfield (Green Line) North 40510
30100 Garfield (Green Line) South 40510
30223 Garfield (Red Line) North 41170
30224 Garfield (Red Line) South 41170
30096 Grand (Blue Line) South 40490
30095 Grand (Blue Line) North 40490
30064 Grand (Red Line) North 40330
30065 Grand (Red Line) South 40330
30148 Granville South 40760
30147 Granville North 40760
30184 Halsted (Green Line) West 40940
30183 Halsted (Green Line) East 40940
30215 Halsted (Orange Line) North 41130
30216 Halsted (Orange Line) South 41130
30189 Harlem-Forest Park East 40980
30190 Harlem-Forest Park West 40980
30004 Harlem (Green Line) West 40020
30003 Harlem (Green Line) East 40020
30145 Harlem (Blue Line-O'Hare Branch) North 40750
30146 Harlem (Blue Line-O'Hare Branch) South 40750
30165 Harold Washington Library-State/Van Buren East (Outer Loop) 40850
30166 Harold Washington Library-State/Van Buren West (Inner Loop) 40850
30285 Harrison North 41490
30286 Harrison South 41490
30176 Howard South 40900
30175 Howard North 40900
30173 Howard North 40900
30174 Howard South 40900
30158 Illinois Medical District West 40810
30157 Illinois Medical District East 40810
30059 Indiana South 40300
30058 Indiana North 40300
30107 Irving Park (Blue Line) North 40550
30108 Irving Park (Blue Line) South 40550
30282 Irving Park (Brown Line) South 41460
30281 Irving Park (Brown Line) North 41460
30015 Jackson (Blue Line) South 40070
30014 Jackson (Blue Line) North 40070
30110 Jackson (Red Line) South 40560
30109 Jackson (Red Line) North 40560
30228 Jarvis South 41190
30227 Jarvis North 41190
30248 Jefferson Park South 41280
30247 Jefferson Park North 41280
30225 Kedzie (Brown Line) North 41180
30226 Kedzie (Brown Line) South 41180
30201 Kedzie (Pink Line) East 41040
30202 Kedzie (Pink Line) West 41040
30208 Kedzie (Green Line) West 41070
30207 Kedzie (Green Line) East 41070
30048 Kedzie-Homan East 40250
30049 Kedzie-Homan West 40250
30219 Kedzie (Orange Line) North 41150
30220 Kedzie (Orange Line) South 41150
30249 Kimball North 41290
30250 Kimball South 41290
30217 King Drive East 41140
30218 King Drive West 41140
30117 Kostner East 40600
30118 Kostner West 40600
30289 Lake North 41660
30290 Lake South 41660
30136 Laramie West 40700
30135 Laramie East 40700
30261 LaSalle East 41340
30262 LaSalle West 41340
30031 LaSalle/Van Buren West (Inner Loop) 40160
30030 LaSalle/Van Buren East (Outer Loop) 40160
30150 Lawrence South 40770
30149 Lawrence North 40770
30204 Linden South 41050
30203 Linden North 41050
30197 Logan Square North 41020
30198 Logan Square South 41020
30251 Loyola North 41300
30252 Loyola South 41300
30052 Main North 40270
30053 Main South 40270
30090 Merchandise Mart North 40460
30091 Merchandise Mart South 40460
30182 Midway South 40930
30181 Midway North 40930
30153 Monroe (Blue Line) North 40790
30154 Monroe (Blue Line) South 40790
30212 Monroe (Red Line) South 41090
30211 Monroe (Red Line) North 41090
30259 Montrose (Blue Line) North 41330
30260 Montrose (Blue Line) South 41330
30288 Montrose (Brown Line) South 41500
30287 Montrose (Brown Line) North 41500
30296 Morgan West 41510
30295 Morgan East 41510
30021 Morse South 40100
30020 Morse North 40100
30126 North/Clybourn South 40650
30125 North/Clybourn North 40650
30078 Noyes North 40400
30079 Noyes South 40400
30034 Oak Park (Blue Line) East 40180
30035 Oak Park (Blue Line) West 40180
30263 Oak Park (Green Line) East 41350
30264 Oak Park (Green Line) West 41350
30297 Oakton-Skokie North 41680
30298 Oakton-Skokie South 41680
30172 O'Hare South 40890
30171 O'Hare North 40890
30254 Paulina South 41310
30253 Paulina North 41310
30200 Polk West 41030
30199 Polk East 41030
30029 Pulaski (Pink Line) West 40150
30028 Pulaski (Pink Line) East 40150
30180 Pulaski (Blue Line-Forest Park Branch) West 40920
30179 Pulaski (Blue Line-Forest Park Branch) East 40920
30005 Pulaski (Green Line) East 40030
30006 Pulaski (Green Line) West 40030
30186 Pulaski (Orange Line) South 40960
30185 Pulaski (Orange Line) North 40960
30008 Quincy/Wells South (Outer Loop) 40040
30007 Quincy/Wells North (Inner Loop) 40040
30092 Racine East 40470
30093 Racine West 40470
30038 Randolph/Wabash North (Outer Loop) 40200
30039 Randolph/Wabash South (Inner Loop) 40200
30120 Ridgeland West 40610
30119 Ridgeland East 40610
30196 Rockwell South 41010
30195 Rockwell North 41010
30080 Roosevelt (Elevated) North 41400
30081 Roosevelt (Elevated) South 41400
30270 Roosevelt (Subway) South 41400
30269 Roosevelt (Subway) North 41400
30159 Rosemont North 40820
30160 Rosemont South 40820
30156 Sedgwick South 40800
30155 Sedgwick North 40800
30017 Sheridan South 40080
30016 Sheridan North 40080
30293 Sheridan North 40080
30294 Sheridan South 40080
30164 South Boulevard South 40840
30163 South Boulevard North 40840
30071 Southport South 40360
30070 Southport North 40360
30037 Sox-35th South 40190
30036 Sox-35th North 40190
30051 State/Lake West (Outer Loop) 40260
30050 State/Lake East (Inner Loop) 40260
30169 Thorndale North 40880
30170 Thorndale South 40880
30069 UIC-Halsted West 40350
30068 UIC-Halsted East 40350
30141 Washington/Wells North (Inner Loop) 40730
30142 Washington/Wells South (Outer Loop) 40730
30073 Washington (Blue Line) South 40370
30072 Washington (Blue Line) North 40370
30098 Washington (Red Line) South 40500
30097 Washington (Red Line) North 40500
30232 Wellington South 41210
30231 Wellington North 41210
30283 Western (Brown Line) North 41480
30284 Western (Brown Line) South 41480
30143 Western (Pink Line) East 40740
30144 Western (Pink Line) West 40740
30043 Western (Blue Line-Forest Park Branch) West 40220
30042 Western (Blue Line-Forest Park Branch) East 40220
30130 Western (Blue Line-O'Hare Branch) South 40670
30129 Western (Blue Line-O'Hare Branch) North 40670
30060 Western (Orange Line) North 40310
30061 Western (Orange Line) South 40310
30106 Wilson South 40540
30105 Wilson North 40540

 

 

Appendix C: Route Direction Code Quick Reference

In the Arrivals API response, you’ll see a train direction (“trDr”) element. These values represent what you might describe as an “operational” direction—it’s not expressive of the physical direction of a train at its current location so much as the big-picture route direction (even though it often coincides).

How a train’s direction is defined here loosely translates to a “northbound” (trDr=1) or “southbound” (trDr=5) direction, it can be a little tricky to imagine how that applies to routes such as the Blue Line.

Also, note that this value represents the current operational direction of the train as of when the prediction was generated, not which operational direction it’ll have once it reaches a given station that it’s predicted to reach. For example, an Orange Line train that’s at Halsted on its way to the Loop will be shown as such, even for predictions at Harold Washington Library-State/Van Buren by which time it’ll have changed to being a train to Midway the moment it enters the Loop.

Here’s a quick reference to help you understand what these values mean, on a per-route basis:

Red Line
1 = Howard-bound
5 = 95th/Dan Ryan-bound

Blue Line
1 = O’Hare-bound
5 = Forest Park-bound

Brown Line
1 = Kimball-bound
5 = Loop-bound

Green Line
1 = Harlem/Lake-bound
5 = Ashland/63rd- or Cottage Grove-bound (toward 63rd St destinations)

Orange Line
1 = Loop-bound
5 = Midway-bound

Purple Line
1 = Linden-bound
5 = Howard- or Loop-bound

Pink Line
1 = Loop-bound
5 = 54th/Cermak-bound

Yellow Line
1 = Skokie-bound
5 = Howard-bound

 

 

Appendix D: Insight into Polishing Your Output from the Experts

While the raw information alone is powerful, it’s helpful to interpret results and present them in such a way that can make them more meaningful for your customers.

 

Delays

The CTA Train Tracker service looks at how long it’s been since a train has moved from one track circuit to the next and identifies delays if a train appears to not be moving.

The “isDly” element is an expression of whether or not we’ve detected the likelihood that a train is delayed. If the value of isDly = 1, then consider indicating that the train is delayed rather than simply representing the last prediction, which might be growing stale (which you could compare timestamps to determine, independently).

 

Schedule faults

The isFlt element in the results indicates what we call a “schedule fault” in the context of Train Tracker. A fault on an ETA that is schedule-based (isSch=1) indicates that the scheduled arrival time given might not be feasible to serve due to the lack of a scheduled departure having occurred. Our system is designed to do some math in order to calculate whether or not a scheduled arrival is feasible based on minimum travel times from a terminal to where the arrival is being estimated for.

Note that this doesn’t necessarily mean that there are delays or that service is not good at the time—it only means that a train didn’t leave when the planned schedule had provisioned. Transit systems are complex and delays are sometimes unavoidable; our transportation managers use a variety of strategies, including making on-the-go schedule modifications, to maintain service levels (particularly during peak periods when trains leave every few minutes) and provide the best possible service. This is normal and provides a better service to our customers.

 

Events that affect prediction quality

Some construction or unplanned events that affect service (particularly if they cause trains to be routed differently than normal) can affect the quality of predictions in Train Tracker. While we work to improve back-end exception handling, we can alert users that the quality of predictions may be affected by a current event (or altogether unavailable). In certain situations where we know the information may be unreliable, we may temporarily stop offering predictions for all or portions of a route, which will also be reflected in the API. Our Customer Alerts API Alerts Feed contains a special “Train Tracker impact” flag (element “ttim”) to indicate when works are affecting prediction quality.

 

Calculating a number of minutes until arrival from this data

To calculate the number of minutes until arrival (so you can say “4 min” instead of 2:35 p.m., for example, we recommend comparing arrT to prdt – this will give you the number of minutes we calculated from when a train last moved into a new track circuit until when it should get to a station.

The reason for this is because the arrival time value is actually based on how long it should take to get from where the train was when its location was last updated in our prediction database, weighted in such a way to improve prediction accuracy, which happens on a frequent cycle.

The reason we represent this information in date-time form is for added flexibility in defining your own logic, as it allows you to show clock times or make computations as you feel is best for your code project, and can be more meaningful if your app doesn’t update very frequently.

Thus, it gives you the control to compare arrT to prdt if you do have the capability to update frequently, but, if not, you might then also consider other, more advanced scenarios, where you weight that comparison against the age of your last update. (It’s your app, so it’s really all up to you!)

Additionally, note that output for the arrT element, at least at this stage in the beta (we are open to your feedback as developers), is a minimum of 60 seconds from most recent prediction generation (trains disappear from result sets once they actually reach the station).

 

Due Trains

We show “due” or “approaching” on trains which are expected to arrive shortly because “1 min” is a very short period of time, and encourage you to consider doing the same.

 

Accessibility

We work very hard to design our Web services to be fully accessible to people with a wide range of levels of ability, including people with limited or no vision, limited mobility, cognitive disabilities and more.

While it’s up to you how to implement our data in your product and to what lengths you go to cater to audiences who are less able to interact with technology than others, we strongly encourage you to take into consideration accessibility implications on whatever platform you write for and to make sure your incorporation of public transit information helps the whole public, to the best of your ability.

We encourage you to catch up on accessibility standards such as those laid out in the Federal Section 508 guidelines, the Illinois Information Technology Accessibility Act (IITAA), as well as staying up on modern Web or software accessibility best practices. It’ll lead to better products for you and everyone who might benefit from them.

 


 

Appendix E: Error Codes

Error codes are given in the event an unexpected request was made or if an error in processing occurred. A good response comes with an error code of 0.

 

Arrivals API Error Codes

Error Code

Error Name

Error Explanation

0
OK
No error.
100
Required parameter [value] is missing.
The query string does not contain one of the required parameters, currently: "mapid or stpid", "key".
101
Invalid API key
The value for the required parameter "key" is not a valid API key.
102
Maximum Daily CTA Train Tracker API usage exceeded.
The number of successful API Requests using the supplied "key" have exceeded the maximum daily value.
103
Invalid mapid: [value]
At least one of the supplied values for the "mapid" parameter is not valid. The first invalid id is returned.
104
Mapid's need to be integers: [value]
At least one of the supplied values for the "mapid" parameter is not an integer value. The first invalid id is returned.
105
Maximum of mapid's you can request is 4.
A maximum of 4 values may be specified for the parameter "mapid". More than 4 were supplied.
106
Invalid Route Identifier: [value]
At least one of the supplied values for the "rt" parameter is invalid. Supported values are: "Red", "Blue", "Brn", "G", "Org", "P", "Pink", "Y".
107
Maximum of rt's you can request is 4.
A maximum of 4 values may be specified for the parameter "rt". More than 4 were supplied.
108
Invalid stpId specified: [value]
At least one of the supplied values for the "stpId" parameter is invalid. The first invalid value is returned.
109
Maximum of stpid's you can request is 4.
A maximum of 4 values may be specified for the parameter "stpId". More than 4 were supplied.
110
Invalid max specified: [value]
A non-integer value was specified for the "max" parameter.
111
Parameter 'max' must be a positive integer.
A value less than 1 was specified for the "max" parameter. The value must be an integer greater than zero.
112
Stpid's need to be integers: [value]
At least one of the supplied values for the "stpid" parameter is not an integer value. The first invalid id is returned.
500
Invalid parameter: [value]
The query string contains a parameter that is not supported by the train tracker API, currently supported parameters are: "mapid", "key", "rt", "stpid", "max".
900
Server Error
A server error occurred.

 
 
Follower API Error Codes

Error Code
Error Name
Error Explanation
100
Required parameter [value] is missing.
One or more of the required parameters is missing. For this API, the required parameters are: “runnumber”, and “key”
101
Invalid API key.
The supplied API key was not a valid API key.
102
Maximum daily Train Tracker API usage exceeded.
The daily usage limit for the supplied key has been exceeded.
500
Invalid parameter [value].
Valid parameters for this API are: “runnumber”, and “key”.
501
No trains with runnumber [value] were found.
The indicated train may have left service or may simply be incorrect.
502
Unable to determine upcoming stops.
The indicated train has an unexpected exit station id, and the system cannot reliably determine which predictions to report.
503
Unable to find predictions
The train exists, however none of the available predictions are for active stations.

 
 
Locations API Error Codes

Error code
Message
Description
100
Required parameter  [value]  is missing.
One of the required parameters (rt, key) was not provided.
101
Invalid API key.
The API key given in the parameter ‘key’ was either not found or inactive.
102
Maximum daily Train Tracker API usage exceeded.
Key usage has exceeded daily limits. Limits are reset at midnight.
106
Invalid route identifier: [value].
Valid route identifiers are: red, blue, brn, g, org, p, pink, y
107
Maximum number of rt’s per request is 8.
No more than 8 routes can be issued per request. Note duplicates are counted but not returned.
500
Invalid parameter: [value]
The indicated parameter is not valid. Valid parameters are: rt, key.

 

 

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Trains:

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Blue Line Normal Service
Brown Line Normal Service
Green Line Normal Service
Orange Line Normal Service
Purple Line Normal Service
Pink Line Normal Service
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