Aldridge furnished and installed new train control, communications, and traction power systems along ballasted, elevated, and subway sections for the Chicago Transit Authority. This included train controls for 20 new interlockings and a bi-directional CAB signal system. The scope included the installation of new relay houses, relay rooms, wayside signal equipment, AC and audio track circuits, train indications, and worker-ahead zones including new express and local signal cable packages throughout the entire system.
Provisions were also made for the future automatic routing of express trains through the Block 37 tunnel, which included an AVI system for train identification. New traction power cables were installed throughout both the Dearborn and State Street subways to enhance the positive and negative power feeds that power the CTA rail cars. A new communications system was installed to ensure consistent and accurate communications between CTA personnel and the control center. New tunnel lighting was installed to increase visibility within the subways, providing a safer environment for evacuation purposes and for personnel working within the subways.