If you want to know how bad traffic is, you’ll likely turn on the radio or check traffic tracker on a Google app.

If the city wants to know, they check a bus.

A widely circulated report by Texas A&M ranked Chicago the 7th worst city for traffic.

While many focused on the pains and complaints of hours spent in a car waiting to get home, we found it interesting to see how the city assesses traffic congestion.

In December of last year, the Mayor’s office issued a press release which formalized the Chicago’s OpenGov initiative.  Also in that release, is the release of data sets related to traffic:

“These datasets include the Chicago Traffic Tracker, which will provide data on traffic congestion on Chicago’s arterial streets in real-time by continuously monitoring and analyzing GPS traces received from Chicago Transit Authority (CTA) buses. Congestion estimates will be produced every ten minutes to measure the current estimated speed for about 1250 segments covering 300 miles of arterial roads.”

That’s right. The city is re-purposing the data that feeds your bus-tracker apps.

If you think about it, it makes sense. You already have a fleet of city vehicles traveling the arterial streets of Chicago. Why not use that very same data and re-purpose it to assess traffic?

The data sets are updated every five minutes.

The city’s data portal outlines possible causes for congestion and interruption on the streets:

“There is much volatility in traffic segment speed. However, the congestion estimates for the traffic regions remain consistent for relatively longer period. Most volatility in arterial speed comes from the very nature of the arterials themselves. Due to a myriad of factors, including but not limited to frequent intersections, traffic signals, transit movements, availability of alternative routes, crashes, short length of the segments, etc. speed on individual arterial segments can fluctuate from heavily congested to no congestion and back in a few minutes. The segment speed and traffic region congestion estimates together may give a better understanding of the actual traffic conditions.”

The end result is the Chicago Traffic Tracker.


Interestingly enough, the data are also fed to the city’s Office of Emergency Management and Communication, which is the city’s nerve center.  Housed in an impressive command center, city officials and employees are able to coordinate events, operate communications systems, and provide technology for services and to city agencies.

—Elliott Ramos

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