International Bridge Technologies

Chicago Transit Authority (CTA) Red-Purple Modernization Project – Chicago, Illinois

Technical details
Chicago Transit Authority

Construction Completed:

Chicago, Illinois
Contractor: Walsh Construction and joint venture partner Fluor Corporation.
SYSTRA IBT’s Role: Detailed design of the segmental concrete guideway. Engineer of Record for the segmental structure.


Total Length: 15,442 m (50,660 ft)

As part of the Walsh-Fluor Design-Build Team, SYSTRA International Bridge Technologies developed a segmental concrete guideway for a major portion of
the US$2 Billion Red-Purple Modernization project in Chicago.

This design required approval of an alternate technical concept that significantly improved upon the baseline steel design. This is the first segmental structure built by the Chicago Transit Authority (CTA). The CTA operates the famous Chicago ‘L’ (short for “Elevated”) rapid transit system, which first began service in 1892 and is well-known for its steel structures.

Significant factors for the concept’s approval included:

  • Improved means to address difficult construction equipment access
  • Compressed construction schedule
  • Reduced initial construction cost
  • Reduced maintenance cost

During the pursuit, SYSTRA IBT showcases distinctive visualization capabilities. The realistic renderings were incorporated in the reviews of the alternate technical concept and were a key factor in communicating the design, construction, and aesthetic concepts to the CTA and the public.

The SYSTRA Bridge Group, SYSTRA Consulting USA, and SYSTRA-DTE also collaborated for this pursuit. In addition to bridge engineering, the team deploys their worldwide rail systems and transit expertise. Due to the unique character of the proposed structure within the Chicago system, it was necessary for SYSTRA to develop a unique stray current protection system that effectively protects both the new closed-deck segmental structure and the adjacent open-deck steel structures.

The ‘L’ is the second busiest rail mass transit system in the United States, and it is an iconic symbol of Chicago. This is a very high-profile win for SYSTRA in North America.

Featured Project

<p style="font-size:10px">Photo credit: CTA</p>
<p style="font-size:10px">Photo Credit: Dave Burk Photography, LLC</p>
<p style="font-size:10px">Photo credit: CTA</p>