Bombardier Transportation Rail Control Solutions: Legacy Systems & Alstom Evolution

While Bombardier Transportation was acquired by Alstom in 2021, the company’s extensive portfolio of rail control solutions continues to operate on thousands of kilometers of track worldwide. Known for its “EBI” heritage, these systems—ranging from CITYFLO urban signaling to INTERFLO mainline solutions—set standards for safety, capacity, and reliability.

This guide examines the technical architecture of these legacy systems and their current standing within the modern railway engineering landscape.

Technical Comparison: CITYFLO vs. INTERFLO

The Bombardier (now Alstom) signaling portfolio is divided into specific product families designed for different operational environments.

CITYFLO: Urban Signaling and Mass Transit

The CITYFLO solution suite is designed for the complex demands of high-density urban transit. Its flagship iteration, CITYFLO 650, utilizes a moving block principle permitted by CBTC technology. Unlike traditional fixed-block signaling, CITYFLO 650 allows trains to run closer together safely, significantly increasing line capacity.

• Moving Block Technology: Reduces headways between trains.
• Flexibility: Can be installed on brownfield sites (existing lines) with minimal disruption.
• Automation: Fully supports Grade of Automation 4 (GoA4), eliminating the need for onboard staff.

INTERFLO: Mainline and ERTMS Solutions

For national and cross-border railways, the INTERFLO series addresses the need for interoperability. Compliant with the European Rail Traffic Management System (ERTMS) standards, these systems ensure seamless travel across borders.

The INTERFLO 450 (ERTMS Level 2) system is particularly notable for high-speed lines. It utilizes GSM-R (Global System for Mobile Communications – Railway) for continuous two-way communication between the train and the Radio Block Centre (RBC), removing the need for physical trackside signals and allowing for higher speeds.

Core Components: The “EBI” Series

Underpinning both CITYFLO and INTERFLO are the modular hardware components known as the EBI series:

• EBI Lock: Computer-based interlocking (CBI) that prevents conflicting train movements.
• EBI Cab: Onboard Automatic Train Protection (ATP) equipment that displays speed profiles to the driver.
• EBI Track: Train detection systems, including axle counters and track circuits.

Editor’s Note: Following the acquisition, these technologies are now supported and further developed under Alstom’s digital mobility division, often integrated alongside Alstom’s native Urbalis and Atlas solutions.