CTA Train Tracker Estimated Arrivals: Notes & Help

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Latest features

Here's what's available in this release of CTA Train Tracker:

  • Estimated train arrival times for stations based on "live" train information, using location data we have for trains that are in service.
  • Estimated arrival times per train, by clicking on a train in a list of station results.
  • Up to two scheduled arrival times are shown when there are only one or no predictions for a given boarding position at your station.
  • An easy-to-use interface designed for quick access to the information you want, whether you're using the desktop or mobile version.
  • Integrated Customer Alerts shown in the event planned work or an unavoidable delay affects service (and/or the reliability of predictions).
  • The ability to customize how information is presented to you. Options include setting how many arrivals are shown, or grouping arrivals by route or track.
  • Text messaging capabilities that allow you to get information from CTA Train Tracker by text.
  • Stops you recently viewed are remembered, and you can flag stops as "favorites" for easy access later.
  • The ability to search for stops by name.
  • The ability to search for stops near you, where location data is available.

In later phases, we'll be adding a number of additional features. Check back here periodically to see what's new!


Stops Near Me

This feature helps you more quickly jump to the info you need, based on your location. Modern phones and web browsers can find your location quickly and with pretty good accuracy by using either GPS hardware or using WiFi hardware to detect nearby hotspots.

If you use this feature, your computer or device will tell us where you are (in latitude and longitude), along with a margin of error and some other info. We then check against our database of train stations to tell you which ones are closest.

If the margin of error is too great, we won't be able to make suggestions, but you can always pick a route and station by name or search for stations, by name.

More info

While this service works really well when you have the right hardware, there are a number of circumstances, due to limitations modern phones have as well as physical barriers (like subways, which are underground and away from the signals that are needed to detect location).

Here are the common types of errors you might receive and why:

  • The info we received wasn't accurate enough.
    If you're underground, in a sturdy building or don't have WiFi or GPS enabled, your browser or device might give us a location, but it might not be precise enough for us to make any suggestions that are likely to be helpful.
  • We don't have permission to see your location.
    Your browser or device has told us we don't have permission. If you'd like us to make a suggestion based on location, if your device asks you whether you'd like us to see your location, you'll need to allow it for this to work.
    Also, some capable devices may be set to reject all location information requests from websites, such as some Blackberry devices--you may need to set your browser options to enable this feature. Also, if you've rejected a request from us in the past, you may need to reset browser permissions in order for you to be prompted again.
  • Information wasn't available to us.
    Your computer or device told us that location information wasn't available. It might not be possible for your location to be detected if you're in certain places, like underground, or don't have a reliable connection to the Internet.
  • The operation timed out.
    If it takes a long time for your location information to be provided to us, the operation can time out. It might work if you try again.
  • A network or server problem occurred.
    If your computer or device doesn't have a reliable network connection, or for some reason our servers couldn't fulfill your request, you won't be able to see suggestions.

Follow this train

When you are looking at a list of estimated arrivals for a station, you can pick the train you plan to board from the list and watch its progress as it approaches you. Then, you can keep watching and see when you'll arrive at the stop you're going to.

When following a train with this feature, you can also then click stations further down-route and see arrivals for that station (which can be especially handy if you're taking a train to a station specifically to transfer to another train).

This data is only available for trains that are in-service (not trains that have yet to depart).


How does it work?

The system behind this service looks at where in-service trains are and makes real-time estimations based on recent travel times from where the train is to upcoming stations. This service also shows scheduled departure times when live estimations are unavailable due to no trains being between you and the terminal (or if at a terminal).

Why does it sometimes show scheduled arrival/departure times?

Real-time estimations are only available for trains once they've left their terminal, which is when we can begin tracking their movements. Until a train leaves its terminal, we show up to two scheduled departure times instead. (At terminals themselves, only scheduled departures are shown.)

Actual departures can sometimes vary from schedule in the event that service is being modified by route managers to maintain even service levels or if some sort of delay to a departure occurs.

In some cases, scheduled arrivals don't provide a specific destination, but a general direction, due to certain system limitations. Once a train leaves and is in service, however, more information, such as specific run number and destination will be shown on its live estimations.

Overnight on lines that do not operate 24 hours, no information will show until the time is within 45 minutes of service.

What does it mean when the results show "---" instead of a train prediction?

An entry that shows "---" indicates a train is expected to be on the way soon, but that we need more information to give you a reliable estimate. It's basically a way to handle the unexpected without giving you information we can't be sure is reasonably reliable.

What does it mean when it says "Delayed"?

This indicates that our system is showing a train as having not moved for a few minutes, indicating a delay is underway to a specific train. Once the train starts moving, estimations for that train will start being shown again.

The website is alerting me that estimations may be affected by something. Why?

Because our computer systems can sometimes have trouble anticipating a train's movements during abnormal operating circumstances, such as when we're individually turning trains or running a single track due to planned work or a disruption to our service, we make this note when something might negatively affect the quality or reliability of arrival estimates automatically generated by our systems.

Because we mean to be careful to avoid giving information that's not likely to be helpful, we may even temporarily disable/withhold arrival estimates rather than merely or warn that they may be affected by event, as a precaution.

How fresh is the information?

It's based on information that's pretty close to real-time. Our database is updated two or three times per minute. In most Web browsers you'll see arrivals update automatically about every 30 seconds.

You can change your preferences when looking at results in Train Tracker to decide whether or not you want the page to auto-refresh (if data usage is a concern for you).

Why does the order of trains at my station sometimes change?

The ‘L’ is a complex rail system with hundreds of miles of track and dozens of track junctions. Estimated arrival times are just estimates based on the most recent, logical guess our computers can make at arrival, based on historical information--but trains can operate a little differently than a computer's best guess, particularly when it comes to which trains proceed first through a human-controlled junction.

For example:

If you're at Clark/Lake and there is an Orange Line train, a Purple Line train, then a Green Line train, based on recent travel times for all three lines with trains approaching your station, our system will estimate how long it'll take for each of those trains to reach you based on recent travel times from where they are to where you are. It might, based on recent, recorded travel times, estimate the Green Line train will come through first, then Purple, then Orange.

However, if the Orange Line train is a little late and the person operating the junction near Clark/Lake gives them priority to help them get back on schedule, it might come into the station first, instead, a little sooner than previously estimated and CTA Train Tracker will re-order its estimations soon after the data refresh.

Why doesn’t CTA Train Tracker tell me if a train is running express?

Right now, this information isn’t available to the Train Tracker system. We’re working on building it in, though, so you’ll better know what to expect wherever you are.

How do I set or un-set a favorite stop?

Simply click the heart next to the stop name when looking at a stop in Train Tracker on our Web site. This works both on desktop computers and most mobile devices. The heart will fill in (with pink) if selected. You can de-select favorites by clicking the heart to make it grey again, anywhere the heart appears.

Why did my favorite or recent stops disappear?

We don't store favorites or recent stops on our servers. Stops you've recently viewed or flagged as a favorite are stored using a "cookie" on your computer or whatever device you use to view our site. If you clear your browser history, including cookies, the information about what stops you've visited or "favorited" is cleared, as well. If you've set your browser to clear cookies every time you close it, or are visiting in a private browsing session, this information will not be stored.

How do I clear favorites or recent stops?

Simply clear your browser's cookies. Note that this will likely clear all information remembered by your browser, such as sites you've logged into and told to remember you.

Why does CTA Train Tracker tell me the train is going toward “Howard or Loop” on the Purple Line or “63rd Street” on the Green Line when showing scheduled arrivals, rather than a specific destination?

Because our field personnel sometimes need to make manual modifications to maintain good service on the system, scheduled departures on the Purple and Green Lines might not be as precise as a live estimation. CTA Train Tracker waits until the train leaves to announce a specific destination, and once it’s left the terminal you’ll see exactly where that train is expected to go.