Honoring Chicago’s Past with a More Resilient and Efficient Transit System

Chicago Transit Authority Red and Purple Line Modernization Project

Chicago Transit Authority (CTA) is investing in a more resilient and efficient transportation system with its $2.1 billion Red and Purple Line Modernization Project (RPM)—one of the largest transit investments in the agency’s history. The project includes replacing four century-old stations along Chicago’s busiest transit corridor with larger facilities that are ADA (Americans with Disabilities Act) compliant. The new stations feature wider platforms, better lighting, improved security, real-time information boards, more reliable train service, less crowded trains and platforms and a more aesthetically pleasing environment for pedestrians.

As part of the Walsh-Fluor Design-Build team, Atlas provided civil engineering services, including roadway design, traffic maintenance, signal design, utility coordination, drainage design, site layouts, and grading, as well as electrical and lighting design.

“Every day, millions of Chicagoans rely on the city’s transit system to get where they need to go. Supporting our long-time client, Atlas was proud to collaborate with CTA on delivering a safer, more reliable transit system,” said Tom Price, Atlas Infrastructure President. “Sustainability, preservation, and innovation were woven into every decision made, resulting in a project that truly honors Chicago’s past, while building a resilient, efficient transit future.”

Building a modern transit system

Construction on RPM Phase One began in 2019 and included updates on two major areas—the Red-Purple Bypass and the Lawrence to Bryn Mawr (LBMM) section. With millions of passengers relying on the Red Line every year, updating these lines was critical to making CTA’s transit system more reliable and efficient.

In 2021, CTA celebrated the completion of the Red Purple Bypass. This milestone allowed northbound Brown Line trains to pass over Red and Purple Line tracks—eliminating a critical bottleneck and allowing for more frequent service.

CTA hit another major milestone in 2025 with the completion of the LBMM portion of the project, which involved reconstructing four stations and replacing all elevated track and support structures along 1.3 miles of the Red Line.

Working within one of the nation’s most spatially constrained urban corridors presents unique challenges. Atlas helped CTA employ highly adaptive planning strategies to overcome numerous complexities throughout this project. To keep trains running on time, our team utilized creative solutions to sequence construction and implement temporary systems, including two fully functional temporary stations that served the public for years before the final stations were finished. Atlas’ team even helped relocate a century-old building to allow critical track realignment—a decision that demonstrated thoughtful engineering and respect for the city’s architectural heritage.

“Together with CTA and our industry partners, Atlas designed every element of construction planning to reduce inconvenience and minimize disruption to people’s daily routines,” added Price. “Atlas is proud to have contributed to this landmark project that will be utilized by millions of passengers in the years to come.”

Working collaboratively with CTA, our team contributed to this massive transit line upgrade through:

• Roadway and alley rehabilitation: Atlas designed plans for all impacted streets and alleys within the project limits and reconstructed all impacted sidewalks to meet Chicago Department of Transportation (CDOT) standards with ADA compliant ramps at all temporary and permanent locations.
• Collaborative planning and permitting: Atlas was responsible for all utility coordination on the project, including identifying potential conflicts early in the design-build process. By maintaining regular contact with utilities throughout the project, Atlas made proactive communication and coordination a top priority. Our team worked extensively with Walsh-Flour to facilitate communication with the Department of Buildings, CDOT, and the Office of Underground Coordination to keep the project running smoothly.
• Digital and technical knowledge: Atlas’ modeling experts created and maintained a dynamic digital terrain model for all surface drainage, roadway vertical geometry and ADA design grades. Our design included extensive OpenRoads work—driving efficiencies and schedule. Atlas was an early adopter of OpenRoads software to create dynamic 3-D models.
• Enhanced safety and lighting: With a deep understanding of CTA’s and CDOT’s requirements, Atlas designed all exterior lighting for the RPB and LBMM sections, as well as power feeds for relay houses, aesthetic lighting, and temporary and permanent lighting for station facades.
• Creative drainage solutions: Atlas designed the Stormwater Management Plan, incorporating CTA’s requirements for collecting and storing runoff. Infiltration trenches and storage tanks were utilized, which eliminated surface runoff contributing to the city sewer system.
• Collaborative construction delivery: Atlas coordinated with Walsh-Fluor, Stantec, and associated subconsultants to coordinate timing on the overall sequence of design packages.

At a glance

CTA’s Phase One investment, one of the largest design-build projects undertaken by CTA

When this corridor was first built, making it one of the oldest in the CTA system

Built with modern architecture and ADA accessibility features

Historically significant Vautravers building moved for track realignment