Red Ahead: Red & Purple Modernization

Red-Purple Bypass rendering, School Street at Wilton.

Red-Purple Bypass Project

What's new?


The new Red-Purple Bypass opened in 2021. The bypass is a key project milestone and component to making our service better for you. 

About the Red-Purple Bypass Project

As part of the first phase of the Red and Purple Modernization (RPM) Program, CTA has completed the Red-Purple Bypass north of the Belmont Station to eliminate a bottleneck that prevents CTA from adding more trains.

The bypass replaces a flat rail intersection, on which all northbound Brown Line trains crossed over the four tracks used by northbound and southbound Red and Purple line trains. The bypass replaces the outdated track configuration (built in 1907) that constrained the CTA’s ability to add train service.


3D Red-Purple Bypass (2020): Contractor project animation

YouTube Video (2015): CTA Has a Plan: Improving Red, Purple and Brown Line Service

YouTube Video (2015): Red Purple Bypass Street Level Animation

YouTube Video (2015): Red-Purple Bypass Track Level Animation

With the new bypass, northbound Brown Line trains will proceed along a dedicated rail line above the Red and Purple line tracks. This improvement will allow CTA to significantly increase the number of trains it runs along the Red Line to reduce overcrowding and meet growing demand for transit service. Benefits of building the Red-Purple Bypass alone include:

  • The addition of up to eight more Red Line trains per hour during rush periods
  • Accommodate up to 7,200 additional customers per hour during rush hour
  • Increased Red and Purple line train speeds by 60 percent through this intersection
  • Customers are saved a half-million travel hours each year

Ridership growth scenarios and current capacity limit at junction (click to enlarge)

The current configuration creates a bottleneck, which if isn’t corrected, will prevent the CTA from adding additional rush period service as ridership grows in the future. This will lead to train overcrowding and more traffic congestion, which could dissuade people from taking transit.


Old configuration (click to enlarge):

Clark Junction's current configuration, showing outbound Brown Line train blocking three tracks

New configuration (click to enlarge):

Clark Junction Configuration after bypass showing trains not interrupted by outbound Brown Line service

Project timeline

  • 2018: Advance utility relocation work begins; CTA selects Walsh-Fluor as design-build contractor

  • 2019: Property demolition complete; construction began on Red-Purple Bypass with start of track foundation work

  • 2021: Red-Purple Bypass completed and put into service

  • 2022: CTA to began reconstruction of North Main lines (Red and Purple Line track structure reconstruction between Belmont and Cornelia/Newport)

  • 2025: North Main Line reconstruction to be completed.

Potential Redevelopment

Some property acquisitions were required as part of this project. Following construction, we will solicit proposals to sell remaining parcels of land for new retail and residential development. There is growing demand for Transit Oriented Development (TOD) in Chicago neighborhoods, and we have already begun working with local stakeholders to begin planning redevelopment of these properties after project work is complete.

For more detailed information please visit the RPM TOD page.

Alternatives Considered

The Red-Purple Bypass Project evolved through six years of planning, consideration of over 20 alternatives, and public outreach efforts throughout every major phase of planning.

CTA considered a number of alternatives to address the capacity constraint at Clark Junction and to reduce property impacts. Further details on these alternatives and reasons for elimination are provided in the environmental documentation prepared for this project and are summarized briefly below. 

Underground Tunnel (Subway)

During very early concept development, CTA examined an underground tunnel. The middle two tracks currently carrying the Red Line would descend into the tunnel immediately north of Belmont station. For operational reasons, Purple Line trains would merge with Red Line trains into the tunnel.

Major Reasons for Elimination

  • Substantially larger project footprint for construction
  • Greater impacts on properties and the community
  • Longer construction duration and greater costs
  • Substantial service disruption during construction
  • Would not allow phasing of the RPM Program

Track 4 Bypass

Track 4 is the easternmost rail track passing through Belmont station, currently used by the northbound Purple and Brown line trains. Northbound Red and Purple line trains would merge onto a single northbound track south of Belmont station. The northbound Brown Line track would ramp upward just north of Belmont station and then curve to the west.

Major Reasons for Elimination

  • Would not eliminate property impacts
  • Introduces a new capacity constraint in the system
  • Would not meet the purpose and need for the project

Bypass using (Red Line) Center Tracks

This alternative would remove the existing conflict between the Red and Brown line trains by creating a bypass for the two center tracks above the existing Brown Line track curve. Because the distance from the north end of the Belmont station platform to the existing crossing would be insufficient for ramp to reach the required vertical clearance, the northbound Brown Line track curve would need to be moved north of its current location. 

Major Reasons for Elimination

  • Would not eliminate property impacts
  • Severe operational impacts during construction
  • Bus shuttles insufficient to meet passenger needs during construction
  • Would not meet the purpose and need for the project

Stacking Tracks

During public outreach efforts, “stacking” the Purple Line tracks over the Red Line tracks was suggested as a potential means to narrow the mainline (north-south) right-of-way requirements in the vicinity of Newport Avenue and reduce property impacts.

Major Reasons for Elimination

  • Longer project length required
  • Wider right-of-way required
  • Would result in greater property impacts
  • Substantial operational issues
  • Visual impact of double-stacked structure

Other solutions, including operational options, were also considered. See the FAQ on the Red-Purple Bypass for further details on these alternatives.

Environmental Assessment

The National Environmental Policy Act of 1969 (NEPA) is a federal law that mandates the consideration of environmental impacts before approval of any federally funded project that may have significant impacts on the environment or where impacts have not yet been determined.

The NEPA process provides a decision-making framework to consider the purpose and need for a proposed action, potential design solutions, project costs, environmental impacts, and relative benefits of the proposed action.

FTA and CTA published an Environmental Assessment (EA) for the Red-Purple Bypass Project on May 19, 2015, established a 30-day public comment period to accept formal comments, and hosted a public hearing for the EA on June 3, 2015.

Based on a review of the EA and all public comments received, FTA issued a Finding of No Significant Impact (FONSI) for this project. The FONSI documentation includes responses to comments received as well as suggested mitigation measures to minimize the environmental impacts of the project, including impacts to historic resources.

Supporting documents related to the EA process are provided below. The issuance of the FONSI means that CTA has identified all potential impacts and ways to minimize and mitigate those impacts and that based on that information, FTA has found that there would be no significant impacts resulting from implementation of this project. The FONSI is required before CTA can receive federal funding to construct the project.
Press Release: CTA Publishes Environmental Assessment for Proposed Bypass as Part of Phase One of Red and Purple Modernization Program (5/19/2015) 
Red-Purple Bypass EA formal Notice of Availability and Public Hearing (.pdf) (.pdf en español) (web version)
Red-Purple Bypass EA Project Summary Booklet (.pdf) (.pdf en español)
Red-Purple Bypass EA (.pdf) (accessible version)
Red-Purple Bypass Section 106 Draft Memorandum of Agreement (.pdf)
Red-Purple Bypass June 3, 2015 Public Hearing Exhibit Boards (.pdf)
Red-Purple Bypass Finding of No Significant Impact (FONSI) (.pdf)

See Project Documents for additional information, including appendices.


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