About AAR Circular Letters
Circular letter summaries are produced monthly by Greenbrier Management Services Group.
AAR circular letters provide information of general applicability to the railroad industry, including proposed and final rules, revisions, standards and recommended practices, and calls for comments. These summaries provide the main points of circular letters issued in the prior month, as well as important implementation deadlines.
For access to the complete circular letter, please go to my.aar.org/circulars. Circular letters are a fee-based service provided by the AAR’s Transportation Technology Center Incorporated (TTCI). You may subscribe online at publications@aar.com or call 719.584.0538.
Implementation Circulars
C-14519
MSRP F, Sensors, S-6101A –Detector Validation Table
Issued: March 13, 2025
Effective: March 13, 2025
This implementation circular is being released to the industry for revisions to the AAR’s Manual of Standards & Recommended Practices (MSRP) Section F – Sensors / S-6101A: Detector Validation Table / Acoustic Bearing Detectors. AAR’s Equipment Health Monitoring Committee (EHMC) voted to progress the standard to implementation following the action of the Wheels, Axles, Bearings & Lubrication Committee (WABL). The implemented standard is attached to the circular.
Modifications will be incorporated in the next issue of the Manual of Standards and Recommended Practices, Section F. Please update your library and be governed accordingly.
C-14524
AAR Manual of Standards and Recommended Practices (MSRP), Section K-II Locomotive Electronics and Train Consist System Architecture, Standard S-9101.V1.3
Issued: March 26, 2025
Effective: March 26, 2025
S-9101.V1.3 specifies an industry-standard architecture that defines the conventions for integrating electrical and electromechanical devices on board new road locomotives. This standard applies to all new road locomotives ordered after January 1, 2012. It also provides guidance for retrofitting older locomotives.
S-9101.V1.3 was Adopted in 2012 and Revised in 2025 and is attached to this circular in PDF format. S-9101.V1.3 will be incorporated into the next issue of the MSRP Section K-II Locomotive Electronics and Train Consist System Architecture. In the interim, please insert the Circular in your copy of the MSRP Section K-II and be governed accordingly.
C-14529
MSRP Section S-III, COUPLER AND YOKE DETAILS, Standards S-107, S-154, and S-164, regarding MSRP references, coupler butt dimensions, and tolerances for E67DE, SBE67DE, and SE67DE couplers
Issued: March 28, 2025
Effective: March 28, 2025
The purpose of this circular letter is to notify the industry of revisions to Section S-III, Standards:
- S-107: Coupler, E Type, E67DE
- S-154: Coupler, E Type, Top and Bottom Shelf, SE67DE
- S-164: Coupler, E Type, Bottom Shelf, SBE67DE
On October 24, 2024, Circular Letter C-14430 was issued to solicit comments. Comments were received and considered by the Coupling System and Truck Castings Committee (CSTCC), which prompted the following changes:
- Added top shelf dimensions to S-154.
- Corrected spelling error in notes section of each standard.
Standards S-107, 154, and 164 are now implemented and effective immediately. This modification will be incorporated in the next issue of the Manual of Standards and Recommended Practices, Section S-III. Please update your library and be governed accordingly.
Call for Comment
C-14518
MSRP F, Sensors, S-6102, Wayside Passing Data Format | Wheel Profile Detector Readings
Issued: March 13, 2025
Effective: 30 days for comment.
The Equipment Health Monitoring Committee (EHMC) is releasing this circular to solicit comments on the proposed modifications to the subject section within AAR’s Manual of Standards & Recommended Practices (MSRP), Section F – Sensors.
The proposed modifications to this standard are specific to Section 2.4.5 WPD Detector Readings – Extension of Readings. See circular for full details.
C-14522
MSRP Section N, Specification M-950A, Universal Wide-Body Bi-Level Fully-Enclosed Auto Rack Car
Issued: March 14, 2025
Effective: 30 days for comment.
The Specially Equipped Freight Car Committee has proposed revisions to Specification M-950A, 9.5 Stenciling:
Stenciling shall be in accord with the MSRP Section C, Standard S-910, latest edition.
The revision is editorial to reflect the change from Section L to Section C S-910. See circular for full details.
C-14521
MSRP Section N, Specification M-950, Universal Wide-Body Tri-Level Fully-Enclosed Auto Rack Car (Low Deck)
Issued: March 14, 2025
Effective: 30 days for comment.
The Specially Equipped Freight Car Committee has proposed revisions to Specification M-950, 9.5 Stenciling:
Stenciling shall be in accord with the MSRP Section C, Standard S-910, latest edition.
The revision is editorial to reflect the change from Section L to Section C S-910. See circular for full details.
C-14520
MSRP Section N, Specification M-951, Portable Bridge Plates for Multi-Level Auto Rack Cars
Issued: March 14, 2025
Effective: 30 days for comment.
The Specially Equipped Freight Car Committee has proposed revisions to Specification M-951, Section 6.0 Markings. See circular for full details.
C-14523
Field Manual, Appendix B Billing Timelines
Issued: March 22, 2025
Effective: 30 days for comment.
At the September 2024 meeting of the Arbitration and Rules Committee, a proposal as advanced by the Specially Equipped Freight Car Committee to revise Field Manual Appendix B to shorten the billing timelines, was reviewed and approved. See circular for the entire text of the proposed revision.
C-14525
DRAFT S-9420.V1.1 ITC Key Management Service, in support of AAR’s MSRP – Section K-V Electronics Environmental Requirements and Systems Management
Issued: March 26, 2025
Effective: 15 days for comment.
The Positive Train Control Interoperability Committee of the Association of American Railroads (AAR) is publishing DRAFT S-9420.V1.1 ITC Key Management Service for review and comment.
The document provides an industry approved specification for Key Management Services (KMS). See circular for full details.
C-14528
DRAFT S-9418.V1.1 PSA-2 Gateway Requirements, in support of AAR’s MSRP – Section K-V Electronics Environmental Requirements and Systems Management
Issued: March 27, 2025
Effective: 30 days for comment.
The Railway Electronics Standards Committee (RESC) of the Association of American Railroads (AAR) is publishing DRAFT S-9418.V1.1 PSA-2 Gateway Requirements for review and comment.
This document only describes the security aspects of PSA-2 as they relate to the Systems Management Gateway. See circular for full details.
C-14527
DRAFT S-9008.V1.1 PTC Security Architecture 2 (PSA-2), in support of AAR’s MSRP – Section K-I Railway Electronics Systems Architecture and Concept of Operations
Issued: March 27, 2025
Effective: 15 days for comment.
The Positive Train Control Interoperability Committee (PTCIC) of the Association of American Railroads (AAR) is publishing DRAFT S-9008.V1.1 PTC Security Architecture 2 (PSA-2) for review and comment.
This document outlines enhancements to the management and exchange of the key material used for communication between a locomotive and the back office and the protection of key material used for communication between a locomotive and a WIU. See circular for full details.
C-14526
DRAFT S-9416.V1.1 ITCSM Agent Requirements to Support PSA-2, in support of AAR’s MSRP – Section K-V Electronics Environmental Requirements and Systems Management
Issued: March 27, 2025
Effective: 15 days for comment.
The Positive Train Control Interoperability Committee (PTCIC) of the Association of American Railroads (AAR) is publishing DRAFT S-9416.V1.1 ITCSM Agent Requirements to Support PSA-2 for review and comment.
This document describes the minimal set of behaviors that a Client must comply with for interfacing with ITC Systems Management. See circular for full details.
Notice of Circulars
C-14516
Car Repair Facility Labor Rate – Effective April 1, 2025
Issued: March 12, 2025
Effective: April 1, 2025
The Car Repair Facility Labor Rate effective April 1, 2025 is $170.81, unchanged from the labor rate estimated on January 1, 2025. This will be reflected in the April 1, 2025 release of the AAR Office Manual.
C-14517
Canadian Car Repair Facility Labor Rate – Effective April 1, 2025
Issued: March 12, 2025
Effective: April 1, 2025
The Canadian Car Repair Billing Labor Rate calculation for April 1, 2025 is $253.33 CAD (Two hundred and fifty-three Canadian dollars and thirty-three cents), an increase of four dollars and seventy-three cents from the calculation for January 1. For comparison purposes, this converts to about $176.01 in U.S. dollars. The change will be reflected in the April 1, 2025 release of the Canadian Price Master.
CPC-1429
AAR M-1002 Current B-2 Forms
Issued: March 19, 2025
Effective: March 19, 2025
As requested by the AAR Tank Car Committee, the documents attached to this circular contain the updated B2 forms used for facility audits.
Economic & Industry Update | March 2025
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