Slow Zone Elimination

Slow Zone Elimination

Putting the rapid back in transit

What's a slow zone?

Track renewal work is a continuing effort in order to remove and prevent slow zones on the CTA 'L' system.

Slow zones are areas where trains are required to operate at slower-than-normal speeds due to track conditions or certain types of conditions. Slow zone elimination work typically involves replacing aging rail ties and tie plates with new ties and plates, if not whole track replacement. In other cases, eliminating slow zones involves structural improvements or improvements to power delivery systems.

The end result of slow zone elimination work is faster and more reliable service and a better, more comfortable commute—when a slow zone is lifted, the speed limit for that area is returned to normal, which, on a straight stretch of track, can be as fast as 55 miles per hour!

See the FAQ below for more about how tracks are laid. 

Slow Zone MapsLooking for slow zone maps?

They're further down on this page.


Eliminating Slow Zones

As a part of regular maintenance, the CTA inspects, detects, and repairs conditions that might require slow zones, such as checking track ties and other infrastructural elements for aging and deterioration. Where tracks rest on ballast (rocks), we also “tamp” the tracks, a maintenance activity that realigns track and stabilizes the ballast supporting the tracks, on a regular and ongoing basis to help prevent slow zones from forming due to track deterioration.

This work is done continually across the entire system, with inspections occurring regularly. Work to maintain and upgrade track and signals often occurs overnight while trains on most routes are not in service, although some work occurs during off-peak hours while service is in operation. When work is expected to affect travel, Customer Alerts are posted online and at stations. Check regularly to see when work might affect your trip.


What slow zone elimination looks like

We regularly post photos of our efforts to make the 'L' better—and there's lots to see. Here's a selection of some photos from over just the last couple of years of track improvements and slow zone elimination work to bring you better service.

See more of the 3,000 photos we've posted on Flickr.


What We’ve Been Doing

CTA has drastically reduced the number and coverage of pre-existing slow zones in recent years, thanks to some ambitious programs to renew and replace aging and deteriorating components of the 'L' system. However, new slow zones will form as other parts of our railway infrastructure and track ages.

Work is ongoing to eliminate slow zones that develop from regular wear and tear, extreme weather conditions and other factors. In addition to regular and ongoing track maintenance and improvement work, this larger slow zone removal project is underway:

Slow Zone Maps

Recent maps

Each file is a PDF.


Historical maps

These are packaged as ZIP files.


Previous slow zone elimination projects

Slow zone elimination work has been completed on several parts of the ‘L’ system as part of several other larger project zones, including:

Ravenswood Connector – Brown & Purple Lines (Armitage to Mart)
Work began in late 2013 on a $71 million project to perform major structural renewal and track improvement work on the Ravenswood Connector, the part of the Brown Line & Purple Line Express between Armitage and Merchandise Mart. Work, which has continued through 2014, will eliminate about two miles of slow zones (as slow as 15 m.p.h.) on tracks that host 700 trains per day. Learn more... 

Blue Line O'Hare Branch & Subways
In 2014, CTA began work to eliminate or prevent slow zones and reduce travel times on the Milwaukee Elevated portion of the Blue Line (which is the elevated line between Logan Square and Division) and in the Kimball Subway (through Logan Square and Belmont) and Dearborn Subway (Division through Clinton). The last major weekend closure for this work wrapped up at the end of August 2014. This work was part of a major investment in the O'Hare Branch of the Blue Line, announced in December 2013 by Chicago Mayor Rahm Emanuel and Illinois Governor Pat Quinn. Learn more: Your New Blue, Milwaukee Elevated Track Renewal

Purple Line Evanston Branch Track Work
Work to rehabilitate the tracks and remove slow zones was completed in December 2013 and included extensive tie replacement, placement of new ballast, and tamping of the track system and roadbed, when work finished between Milburn (near Central) and the north terminal at Linden. This followed work in a phase that was performed between Church and Milburn interlockings in the summer and fall of 2013. This project was undertaken in several phases over the course of seven months using existing resources and was performed by CTA personnel in our Track and Structure departments. Work was performed overnight and on weekends and under single-track conditions (not requiring major track closures).

Red Line South Reconstruction (Dan Ryan Track Renewal)
From May thru October, 2013, we rebuilt the tracks along the South Side Red Line, from Cermak-Chinatown to 95th/Dan Ryan—a project that is providing faster, more comfortable and more reliable service for Red Line riders. Crews replaced everything in the track bed: ties, rail, third rail, ballast (the stone material that holds the ties in place) and drainage systems. The project included station improvements and made the remaining stations on Red South accessible to people with disabilities. Learn more...

Red & Purple Lines: North Side Main Line (Belmont to Howard)

Partial slow zone elimination was completed in 2008. Work was also completed in the area of Sheridan station, with slow zones around the station removed in December 2009. In 2010, work was completed eliminating existing slow zones between Addison and Wilson. In late 2011, Mayor Emanuel and Governor Quinn announced a $1 billion investment in the Red Line, which included some track and tie replacement and viaduct repair work on the North Side Main Line, eliminating approximately 7,000 feet of slow zones and speeding up service on the Red Line and Purple Line Express. Much of this work was done as part of the Red North Station Interim Improvements project.

Green Line Ashland Branch (+ (also used by rerouted Red Line during Dan Ryan Track Renewal)
Significant work was done to eliminate slow zones in Spring 2013, including track tie replacement work, on the South Side Green Line in anticipation of rerouted Red Line service to Ashland/63rd during track renewal on the Dan Ryan line.

Loop Track Renewal
In 2012 and 2013, the second phase of major work was done to ensure safe and efficient operations on the Loop ‘L’, focusing on the Wells and Van Buren legs of the Loop, replacing tracks, ties and other elements. Major work was performed on and near both Loop junctions (Towers 12 and 18). Work continued during Wells Street Bridge Replacement work and, as part of this second phase, work to repair and eliminate slow zones just north of the Loop at the Hubbard St. curve was also completed.The earlier phase of Loop Track Renewal was completed in 2008 on the Lake and Wabash sides of the Loop.Learn more: Loop Track Renewal, Wells Street Bridge

Purple Line Viaduct Work
In September 2011, work began on the $15.5 million Purple Line Viaduct project, which will reduce slow zones and improve travel times for Purple Line customers by replacing three aging viaducts along the line at Greenleaf, Dempster and Grove streets in Evanston. Viaduct work also includes new abutments, retaining walls, foundations, and new waterproofing and drainage systems. Other project work includes rail tie replacement, new landscaping and lighting enhancements under the bridges. The majority of project work was complete by summer 2013. Learn more...

Red Line, State Street Subway
Work was done in the area between north portal of the State Street Subway (north of North/Clybourn) and Roosevelt. Almost 3.5 miles of slow zones were eliminated until completion in 2008. Work was also done in February 2013 to eliminate slow zones by making track improvements across a handful of locations in the State Street Subway that needed maintenance from regular wear & tear and some heat damage sustained in 2012.

Blue Line, O'Hare Branch between Addison and O'Hare
Track renewal and slow zone elimination work was completed in December 2008. Over 21 miles of track were renewed and over 18 miles of slow zones were eliminated.

Blue Line, Dearborn Subway
Slow zone elimination in the Dearborn Subway began during 2007 and 2008, when track tie replacement and other improvements were made between the Dearborn Subway's north portal (located between Damen and Division) and Clark/Lake to eliminate existing slow zones that were substantially impacting travel times. The first phase of work resulted in the replacement of over 5,000 deteriorated wooden track ties with concrete ties in areas where slow zones existed.A larger project funded by the Federal American Recovery and Reinvestment Act during 2009 and early 2010 upgraded tracks and track ties along the full length of the Dearborn Subway, from Damen to UIC-Halsted. Many track components in the subway, including aging track ties, were replaced to provide even more reliable service in the future.

Brown Line, Ravenswood Branch from Southport to Western
Slow zone elimination completed October 2008 included major tie replacement work to eliminate slow zones through the elevated portions of the branch.


Slow Zone Elimination

What goes into laying 'L' tracks?

Why are there slow zones on the 'L'?

Slow Zone Elimination

Q: What goes into laying 'L' tracks?
A: Railroads typically have two rails on which trains run, and are held in place by being affixed to track "ties." Ties can be made of wood, plastic or concrete. Tie plates are affixed directly to the track ties at a precise distance, and the rails are, in turn, are affixed to the ties by the tie plates.

The 'L' (like many other rapid transit systems) also has a "third rail" off to the side of the running rails, which is how electrical power is delivered to the trains.

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Q: Why are there slow zones on the 'L'?
A: Slow zones are instituted in areas where train speeds should be restricted to maintain safe travel. Commonly, this occurs in a section of track that is beyond its service life and in need of repair or replacement. Slow zones are also sometimes established temporarily in work zones over a period of ongoing construction work.

We take your safety very seriously, and continually inspect our railways for signs of deterioration. If track inspectors (or high-tech track-measuring equipment used for inspection) detect advanced wear or potential defects, a temporary slow zone may be put in place (or other, appropriate action taken), pending repair work.

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