The Chicago Traffic Tracker(beta) website is presented by the Chicago Department of Transportation
(CDOT). The beta version of the website provides realtime traffic conditions on the arterial streets, Average Daily Traffic (ADT) volumes,
traffic signal locations, pedestrian counts, and automated red-light enforcement
program intersections throughout the city. As the site develops we will enhance the website features with travel times, live images from traffic cameras,
planned and un-planned roadway incidents and much more.
Realtime Arterial Traffic
Arterial traffic condition is estimated utilizing realtime GPS probes received from transit buses operated by Chicago Transit Authority (CTA).
CDOT currently monitors congestion levels on about 300 miles of principal arterials streets. Speed is estimated in half mile segments
for each direction of travel. There are about 1,200 segments representing the 300 miles of roadways. A reliable number of GPS traces are required for
estimating speed for a segment. As a result during off-peak hours(mid-day, nights, and weekends) speed status is
not shown on the map for many of the monitored segments.
Speed Color Codes
over 20 mph
10 to 20 mph
below 10 mph
The segment speed color code on the map is based on the speed limit of the street segment. On most of the city streets, with few exceptions, the speed is limited to 30 mph.
Consequently the congestion map shows green for speed above 20 mph, yellow/orange for 10 to 20 mph and red for speed below 10 mph.
The segment level speed layer(red, yellow, or green lines) shows the current speed on a particular half mile segment and the congestion layer shows generalized traffic conditions on 29 distinct
sections (traffic zones) of the city. There is much volatility in the arterial segment speed. However the congestion estimates for the traffic zones
remain consistent for relatively longer period. The “Typical” option for Congestion Outlook (on top left) shows the average of the last 100 days of historical traffic conditions for the time of the day and the day of
the week on which the request is made. The congestion projection for the next 12 hours is based on historical averages for the time of the day and day of the week adjusted to the
actual traffic conditions experienced in the last few hours. This option is defaulted to the next hour (“In 1 hr”). Use the dropdown arrow to select congestion projections for up to
12 hours in advance. Note that the congestion estimates are for arterial(non-freeway) streets only. It is possible to have free flow conditions on arterial streets in a traffic zone while the freeways passing
through that zone is congested or visa-versa. In the future ChicagoTrafficTracker will offer freeway conditions as a separate map layer.
The segment speed and zonal congestion estimates are based on the speed of the probe vehicles in the last 10 minutes. As a result the current speed and congestion value for a segment or zone is more probabilistic
than actual. Occasionally bad data or unexpected behavior of a probe vehicle can skew the segment speed to be higher or lower. However, 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 arterial segments can fluctuate from
heavily congested to no congestion and back in a few minutes. The segment speed and zonal congestion estimates together may give a better understanding of the
actual traffic conditions. There is a likelihood of hitting slower speed on a segment on a congested traffic zone even though the map shows free flow
conditions for the segment at the moment. Conversely the slow speed currently shown for a segment may change shortly if the generalized condition for the traffic zone shows
free flow. Despite the volatility in arterial speed this map should act as a good reference to compare segments or routes within the same traffic zone.
It is highly likely that a traveler will experience higher speed on a segment that is currently showing higher speed on the map compared to travelling on
another segment within the same traffic zone that is currently showing slower speed.
The traffic conditions are updated automatically on this page every 5 to 10 minutes or when a user performs certain actions on the page. The "last updated time" at the top of the screen shows the last time map was updated.
In the near future CDOT plans to provide traffic conditions on all the major streets in the City. Preliminary work is being done to supplement GPS feeds from CTA buses with
other forms of GPS probes and vehicle detection systems.
Average Daily Traffic (ADT)
Average Daily Traffic refers to the number of vehicles traveling through a particular point on the city streets in a 24-hour period.
Counts were taken at various locations throughout the city in 2006. The map on this website displays all of these count locations.
The map must be zoomed in to a "Zoom Level" of 16 or above to display all of the counts.
Each number on the map shows the total number of vehicles that passed through a count location in a 24-hour time period on the day the count was taken.
The actual number of vehicles passing through these locations will be different each day depending on the day of the week, time of the year, weather, and
The number includes a count of vehicles traveling in both directions of traffic for bidirectional streets
and one direction for one-way streets. For additional information on an ADT count, click on the ADT number on the map.
A popup window will show the address where the count was taken, date of the count, number of vehicles traveling in each direction, and the total number of
vehicles traveling in both directions.
The Traffic Count ID # on top of the popup window is provided for reference purposes only.
Chicago has about 2900 traffic signals throughout the city. About 470 of these signals are interconnected through a fiber-network that facilitates the centralized
monitoring and control of signal operations. Whether interconnected or not-interconnected, the signals are programmed to synchronize with
signals immediately around it so that vehicles will pass through the intersections most efficiently. New signals are added and old signals are modernized
every year depending on the need and availability of funds. While OEMC/Traffic Management Authority is responsible for maintaining the signal coordination
and timing, Division of Electricity at CDOT is responsible for the maintenance
of the signals, and CDOT is responsible for the physical design, construction, and timing of signals.
Public can address questions and concerns on traffic signal operations by
calling the 311 or by submitting an online service request.
Red Light Cameras
The number one priority of the red light camera program at CDOT is the safety of our residents. In 2003, Chicago launched its red light camera pilot program to
address an increase in fatal motor crashes at traffic signals. Using traffic crash data collected by Chicago Police, ten intersections were selected and cameras were installed. Since those
intersections were equipped with cameras, there has been a 24 percent average reduction in red light accidents. Currently, Chicago has 190 intersections
with cameras, and these intersections are seeing a 59 percent average reduction in red light running. The fine for running a red light is $100. For more
information on a red-light ticket or to view your violations visit the Department of Revenue's website .
Downtown Pedestrian Counts
The Chicago downtown pedestrian traffic counts were conducted by CDOT in the summer of 2007. The counts were confined to the Central
Business District and nearby shopping and entertainment areas on the north, south, and west sides. While most of the counts
were taken from 7:45 a.m. to 5:45 p.m., several of the counts north of the Chicago River were taken from 12:30 p.m. to 9:30 p.m.
All of the counts on the map are from weekdays and are mid-block counts. Click on the pedestrian count number on the map for the exact
count, the count's exact duration, and location (including the side of the street). For most locations, a count was taken on
both sides of the street. The number on the map shows the count from only one side of the street and is displayed in thousands.
The entire 2007 downtown pedestrian count project report with detailed analysis is available on the CDOT website:
For additional information on the Chicago Traffic Information website project contact CODT Division of Project Development at: 30 N LaSalle St, Suite 500, Chicago, IL 60604. PH: 312-744-7650
Feedback and comments may be addressed to: TrafficTracker@cityofchicago.org