The customer alerts API allows for querying data from the transitchicago.com customer alerts database. The response from our server is a well-formed XML document. The database is the backbone of the alerts system on the Web that powers system status information, alerts content on route pages, and RSS feeds.
Alerts are added and updated throughout the day. Each entry is marked for how it affects services, ranked based on its level of impact on services, has descriptive headlines and text, and is associated with both routes and stations which are notably affected by the issue. This allows the information to be processed for a variety of uses, and also powers what we think is a highly-detailed, rich API.
This feed is documented in the following accessible PDF:
Customer Alerts API Documentation (.pdf)
Q: Where does the alert information come from?
A: Data in this system is manually entered into our communications systems by people who work at CTA, as information becomes available or known about something that can affect a service.
For planned work (such as construction-related activity, planned service changes, etc.), we generally enter this information in advance of events.
For unplanned incidents that affect service, such as when a street blockage requires us to reroute buses, the information is entered from our control center—a sort of nerve center for our 220+ mile rail system and ≈150 bus routes.
Information, once entered, appears on transitchicago.com, in our RSS feeds and in this API, in Bus Tracker, and in other places almost immediately.
Q: How timely is this information?
A: We try to enter alerts about planned reroutes and work as far in advance as possible--usually at least a couple of days in advance of an event that will affect service.
When an unexpected incident occurs, we try to have it online as quickly as we can. These events are entered by staff in our Control Center. Alerts may be modified several times throughout the course of an unplanned incident, as additional information and options become available, or as a situation changes.
Q: Is the route status information automatic?
A: Yes, to the extent that alerts that have been entered in our database have start times. A route's "status," per the Route Status API, is based on which alerts in the database are presently active, based on start and end times.
See Further Reading for more information about how you might use this feed, pointers and more! Also, be sure to check out our other information feeds, including the Bus Tracker API and the GTFS Feed.