Sparks on track renewal work

Slow zone elimination

Putting the rapid back in rapid 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 in the event that a track condition has developed or other temporary concerns. 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 MapLooking 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've posted lots of photos of our efforts to make the 'L' better over the years. Here's a selection of some photos from over just the last few years of track improvements and slow zone elimination work to bring you better service.

Examples of Track Improvements & Slow Zone Elimination

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. Because most of our services operate 21-24 hours on most days work typically happens overnight, on weekends, or midday to allow for work to proceed efficiently and with minimal disruption to service, which operates between 21-24 hours on most lines, most days.

See Customer Alerts and sign up for CTA Updates to get planned weekly service change e-mails for details about when track maintenance work will affect service on your line.

Recent larger track projects

Sometimes larger projects are done as a result of track conditions which have formed, other times they may be done because tracks in an area are due for replacement or even as a preventative measure.

Learn about some of the larger, recent track renewal projects.

Slow zone maps

Recent maps

PDFEach file is a PDF.


Earlier years

System status snapshot
‘L’ route status
Red Line
Normal Service
Blue Line
Normal Service
Brown Line
Normal Service
Green Line
Normal Service
Orange Line
Normal Service
Pink Line
Normal Service
Purple Line
Normal Service
Yellow Line
Normal Service
Bus routes w/alerts
Elevator alerts