Signalization for Commuter Railroad


In 2021, PSA started work on one of the busiest commuter railroads in North America serving 200k+ passengers a day. To cope with ever-growing passenger traffic, one of the most heavily trafficked rail sections needed to be modernized with a cutting-edge rail signaling solutions to reduce failures and simplify maintenance. All locations were non-electrified territories operating under the automatic block and manual block signal rules.


Client Challenge

Modernize the loaded railroad section to provide seamless passenger travel with ever-growing traffic.

Project Objective

Upgrade signaling system for 14 miles of double track and 3 miles of single track of the commuter railroad that includes 7 passenger stations while keeping the trains going.


In strict adherence with the client’s instructions and processes, AREMA, and FRA guidelines, the PSA signaling engineering team implemented a microprocessor-based signaling system for the requested railroad section. 

During the project, we were dealing with both AC and DC track circuits. The complexity of the design activities was due to the following railroad elements: 

  • grade crossings using audio frequency overlay circuits

  • electrically locked siding switches

  • electrically locked hand-thrown crossovers

  • new holding signal Control Point

  • upgraded interlocking, from relay to PLC

  • tie-in revisions at existing interlockings

Due to disorganized and outdated existing drawings, PSA provided extensive review to minimize excessive iterations caused by inconsistencies between documentation and onsite situations. 

In the output, PSA provided the client with all the documents required to launch the upgraded rail line:

  • drawings for the upgraded rail section with power calculations 

  • software documentation to execute interlocking logic 

  • datasheets to perform FAT and SAT

  • hook-up drawings 

  • as-in-service documentation describing the complete system

To ensure proper operation of the interlocking for all the scenarios, we utilized a simulator checking the program logic. 

For now, the client is preparing for the commissioning of the modernized rail line. The PSA team provides complete support both remotely and onsite as required for the line to be launched on time.

To explore more technical details click here.

Development Included

  • Hardware design
  • Power calculation
  • Software design
  • ASR calculation
  • SWD simulation
  • Datasheets development
  • TMI, Hook-ups
  • Remote/On-site support
  • AIS documentation development



  • Complete modernization of signaling system for 17 miles / 7 stations

Technology Breakdown

Project size
  • 6 people
  • From February 2021 to present

Further Cooperation

PSA is involved in multiple client's projects on rail signaling design around the world. To explore more, check out our Modernization of Suburban Rail and CBTC for the Rapid Transit stories.

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