Modernization of Suburban Rail


Since 2017, PSA has been involved in the modernization of one of the busiest suburban rail lines in North America. 15 miles of the rail line connecting 2 cities would be upgraded to service 120,000+ people per weekday. This rail line is also used for commercial freight services, which requires increased reliability of its rail signaling solutions.


Client Challenge

Replace the obsolete signaling system to ensure PTC requirements and joint rail services without interrupting transportation processes in the metropolitan area.

Project Objective

Implement a microprocessor-based interlocking system for part of the existing suburban rail line.


For reliable operation of the rail line, the PSA team has designed a microprocessor-based signaling system in view of track zoning, which provides separate control of track groups at each location. It allows stations to continue operating in case any interlocking controller responsible for a particular zone runs out of service, and utilizes adjacent tracks for train passage. 

To complete the signaling upgrades, we ensured the following:

  • Interlocking functions on 9 stations of the rail line

  • Tie-ins with 2 bridges and a relay-based system

  • Seamless communication between rail stations

  • Modernization of power supply for fully upgraded stations

  • Cab coding implementation

To provide station-by-station modernization and smooth commissioning, our engineers ensured the connectivity between upgraded stations and old stations that operated on relay-based systems. 

For rail locations with track development changes, we provided a step-by-step connection of elements. Signaling systems for such stations simultaneously serve initial and updated track development – with added switches, tracks, bridges, etc. When the infrastructure elements are added or eliminated during the project, we need only close a respective jumper to provide a new mode of operation. This function was provided in advance at the design stage.

The PSA team created the documentation package for the upgraded section of the rail line including the book of plan, application logic files, and datasheets for testing. During the project we provided:

  • HW design in accordance with the client’s standards

  • Complete control for 3rd party CAD department

  • Programming of interlocking controllers

  • Power calculations for all the locations

  • Onsite and offsite support while FAT and SAT

The new signaling system is commissioned in night testing mode. All the changings are put in real-time by the client’s request.

To explore more technical details click here.

Development Included

  • Hardware Design
  • Software Design
  • CAD Drawings Reviews
  • HW/SW Change Orders Implementation
  • Documentation Creation
  • Power Calculations
  • FAT & SAT Assistance


  • New infrastructure for 15 miles (9 stations) of suburban rail

  • Mixed passenger and freight service without risk of delays

  • Signaling failures were reduced by 25%

Technology Breakdown

Project size
  • 3.5 Signaling Engineers
  • July 2017 – March 2023

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