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-14765
Subject: Implementation of Revisions to MSRP E BRAKES AND BRAKE EQUIPMENT, S-4027, Automated Single Car Test Equipment, Conventional Brake Equipment—Design and Performance Requirements. Data validation enhancements.
Summary: This circular letter notifies the industry of revisions to Section E, S-4027 Automated Single Car Test Equipment, Conventional Brake Equipment—Design and Performance Requirements, enhancing accuracy and consistency of test data to facilitate compliance with Federal Railroad Administration requirements. The changes do not modify the test process or technical requirements of the codified standard and include an Appendix providing output file requirements in tabular format.
Date: 04-13-2026
Effective Date: 04-13-2026
Call for Comment
C-14763
Subject: Solicitation for Comments – Revision to MSRP Section N, Specification M-970, Condition-Based Certification of Multi-Level Auto Rack Cars
Summary: The Specially Equipped Freight Car Committee has proposed a revision to Specification M-970, Section 2.7.1 to reduce the blasting specification to NO. 7 for certain areas of an auto rack painted with waterborne paint within 15 years of the new or recertified date. The revision details the current and proposed blasting requirements and invites comments under the provisions of AAR Standard S-050, with a 30-day comment period for final action on the proposed revisions.
Date: 04-09-2026
Comment Period: 30 Days
C-14764
Subject: Solicitation of Comments: Revisions to MSRP F, Sensors, S-920, AAR Component Identification (CID) Bar Code Standard – Appendix I (Tank Car Safety Relief Devices)
Summary: The Equipment Health Monitoring Committee (EHMC), in coordination with the Component Tracking Taskforce (CTTF) and the AAR Tank Car Committee, is issuing this circular to solicit industry comments on a proposed revision to Appendix I – Tank Car Safety Relief Devices in the AAR Manual of Standards and Recommended Practices (MSRP), Section F – Sensors. The proposed revision introduces additional data elements and clarifying requirements for specific categories of tank car safety relief devices being added to the Component Registry by the Tank Car Committee, including combination devices, rupture disk devices, and vacuum relief valves.
Date: 04-10-2026
Comment Period: 30 Days
C-14767
Subject: Solicitation of Comments for Revisions to MSRP Section E, BRAKES AND BRAKE EQUIPMENT, S-344, Brake Beam Specifications and Tests, Revisions to the finished condition of brake beams
Summary: This circular letter solicits comments for revisions proposed to Section E, S-344, Brake Beam Specifications and Tests. The proposed change requires manufacturers of brake beams to ship them with a rust-inhibitive coating, with changes highlighted in the attached draft.
Date: 04-13-2026
Comment Period: 30 Days
C-14768
Subject: Solicitation of Comments, Revisions to Field Manual, Rules 3 and 4, Relayed Systems
Summary: At the April 2026 meeting of the Arbitration and Rules Committee, a proposal as advanced by the Brake Systems Committee, to revise Field Manual Rules 3 and 4 to address relayed systems, was reviewed and approved. The document details the current and proposed rules regarding single car tests and 4-pressure capability exemptions for cars configured with relayed systems.
Date: 04-17-2026
Comment Period: 30 Days
C-14769
Subject: Solicitation of Comments, Revisions to Field Manual, Rule 3.E, Prohibition of Non-Slack Adjuster Equipped Truck Mounted Brake Systems
Summary: At the April 2026 meeting of the Arbitration and Rules Committee, a proposal to revise Field Manual Rule 3.E to address the prohibition of non-slack adjuster equipped truck mounted brake systems was reviewed and approved. The revision specifies that cars with such brake systems will become cause for attention at any time, effective January 1, 2031.
Date: 04-17-2026
Comment Period: 30 Days
C-14770
Subject: Solicitation of Comments, Revisions to Field Manual, Rule 17, Couplers, Type E/F and Parts
Summary: At the April 2026 meeting of the Arbitration and Rules Committee, a proposal as advanced by the Coupling System and Truck Castings Committee, to revise Field Manual Rule 17 to address pin/bolt requirements, was reviewed and approved. The entire text of the revision is attached to the circular.
Date: 04-17-2026
Comment Period: 30 Days
C-14771
Subject: Solicitation of Comments, Revisions to Field Manual, Rule 48, Field Repairs on Truck Side Frames
Summary: At the April 2026 meeting of the Arbitration and Rules Committee, a proposal was reviewed and approved to revise Field Manual Rule 48 by adding the removal of unit guide end walls to M-214 as an approved field repair with car owner permission. The revision details the correct repairs on truck side frames, including removal procedures and temperature cautions, up to the point where attachments are mentioned.
Date: 04-17-2026
Comment Period: 30 Days
C-14772
Subject: Solicitation of Comments, Revisions to Field Manual, Rule 53.A.2
Summary: At the April 2026 meeting of the Arbitration and Rules Committee, a proposal to revise Field Manual Rule 53 was reviewed and approved. Comments are solicited in accordance with Rule 123 and should be sent within 30 days for consideration, with a targeted implementation date of July 1, 2026.
Date: 04-17-2026
Comment Period: 30 Days
C-14773
Subject: Solicitation of Comments, Revisions to Field Manual, Rule 66 and Rule 83
Summary: At the April 2026 meeting of the Arbitration and Rules Committee, a proposal was advanced by the Car Repair Billing Committee to revise Field Manual Rules 66 and 83 to remove Why Made Code 44, which was reviewed and approved. The document details the current and proposed changes to Field Manual Rules 66.F.6, 66.F Job Code 5500, and 83.17, and solicits comments within 30 days for consideration.
Date: 04-17-2026
Comment Period: 30 Days
C-14774
Subject: Solicitation of Comments, Revisions to Field Manual Rule 80 and Office Manual Rule 88
Summary: At the April 2026 meeting of the Arbitration and Rules Committee, a proposal as advanced by the Equipment Engineering Committee to revise Field Manual Rule 80 and Office Manual Rule 88 was reviewed and approved. The document details the proposed changes to these rules including causes for attention and removal of certain requirements.
Date: 04-17-2026
Comment Period: 30 Days
C-14775
Subject: Solicitation of Comments, Revisions to Field Manual, Rules 19 and 20
Summary: At the April 2026 meeting of the Arbitration and Rules Committee, a proposal as advanced by the Coupling System and Truck Castings Committee, to revise Field Manual Rules 19 and 20, was reviewed and approved. The entire text of the revision is identified in the circular.
Date: 04-17-2026
Comment Period: 30 Days
C-14776
Subject: Solicitation of Comments, Revisions to Field Manual Rule 73, Hatch Covers and Outlet Gates
Summary: At the April 2026 meeting of the Arbitration and Rules Committee, a proposal as advanced by the Equipment Engineering Committee to revise Field Manual Rule 73 to include outlet gates, was reviewed and approved. The entire text of the revision is identified in the circular.
Date: 04-20-2026
Comment Period: 30 Days
C-14778
Subject: Solicitation of Comments for Revisions to MSRP Section E, BRAKES AND BRAKE EQUIPMENT, Standard S-401, Brake Design Requirements. Revisions to installation instructions, guidance for Groups T and U Hand Brakes
Summary: This circular letter solicits comments for revisions proposed to Section E, Standard S-401, Brake Design Requirements, including changes to dimensions, installation instructions, and guidance for Groups T and U Hand Brakes.
Date: 04-21-2026
Comment Period: 30 Days
C-14779
Subject: Solicitation of Comments, Revisions to Office Manual, Rule 103, Joint Inspection Certificate
Summary: At the April 2026 meeting of the Arbitration and Rules Committee, a proposal to revise Office Manual Rule 103.B.9.e was reviewed and approved. The revision details the procedure for JIC submitted in accordance with Rule 103.A.1.a to the damaging railroad’s JIC – Foreign Car Contact, including timelines and documentation requirements.
Date: 04-22-2026
Comment Period: 30 Days
C-14781
Subject: Solicitation of Comments for Revisions to MSRP Section E, BRAKES AND BRAKE EQUIPMENT, Standard, S-491, Hose Couplings, Revisions to plating and related testing requirements
Summary: This circular letter solicits comments for revisions proposed to Section E, Standard S-491, Hose Couplings, which include prohibiting cadmium plating, providing new replacement plating guidance, and related testing requirements. Changes are attached to the circular.
Date: 04-22-2026
Comment Period: 30 Days
C-14782
Subject: Solicitation of Comments: Revisions to MSRP F, Sensors. S-6101B Industry Data Validation: Wheel Impact Load Detector (WILD)
Summary: The Equipment Health Monitoring Committee (EHMC) is requesting comments on a proposed addition to the subject standard. When S-6101B was originally published in 2025, Section 11.1 did not specify the party with primary responsibility for submitting test results to EHMC, unlike Section 2, which clearly identifies responsible parties. To address this omission and avoid potential confusion, EHMC proposes a revision to the submission and evaluation requirements.
Date: 04-22-2026
Comment Period: 30 Days
C-14783
Subject: Solicitation of Comments, Revisions to Field Manual, Rules 16 and 59
Summary: At the April 2026 meeting of the Arbitration and Rules Committee, a proposal as advanced by the Equipment Engineering Committee to revise Field Manual Rules 16 and 59, was reviewed and approved. The entire text of the revision is attached to the circular.
Date: 04-22-2026
Comment Period: 30 Days
C-14784
Subject: Solicitation of Comments for Revisions to MSRP Section E, BRAKES AND BRAKE EQUIPMENT, Standard S-400 Brake Equipment-Installation Specifications, Revisions to the prohibition of specific shackles
Summary: This circular letter solicits comments for revisions proposed to Section E, Standard S-400, Brake Equipment-Installation Specifications, specifically prohibiting the use of a double clevis shackle that uses cotter pins on the hand brake rigging. Changes are attached to the circular.
Date: 04-24-2026
Comment Period: 30 Days
C-14785
Subject: Solicitation of Comments for Revisions to MSRP Section E, BRAKES AND BRAKE EQUIPMENT, Standard S-439, Hose Clamps, Revisions to plating and related testing requirements
Summary: This circular letter solicits comments for proposed revisions to Section E, Standard S-439, Hose Clamps, which include prohibiting cadmium plating, providing new replacement plating guidance, and related testing requirements. Changes are attached to the circular.
Date: 04-24-2026
Comment Period: 30 Days
C-14786
Subject: Solicitation of Comments for Revisions to MSRP Section E, BRAKES AND BRAKE EQUIPMENT, Specification M-927, Hose Fittings and Hose Assemblies, Air, Wire Reinforced, Revisions to plating and related testing requirements
Summary: This circular letter solicits comments for proposed revisions to Section E, Specification M-927, Hose Fittings and Hose Assemblies, Air, Wire Reinforced. The revisions prohibit cadmium plating, provide new replacement plating guidance, and related testing requirements, with changes highlighted in the attached draft.
Date: 04-24-2026
Comment Period: 30 Days
Notice of Circulars
C-14761
Subject: Informational Circular – Multi-Level Pool Billing (MLPB) Auto-Credit
Summary: Multi-Level Pool Billing will have a go-live date of April 15, 2026 for the auto-credit feature. Any exceptions that remain unanswered after 210 days from the DX outbound date will result in an automatic credit of the total invoice amount to pool participants.
Date: 04-08-2026
Effective Date: 04-08-2026
C-14762
Subject: Registration is Open for NARMO 2026
Summary: The 39th North American Railcar Mechanical Operations (NARMO) Seminar will be held August 31 – September 3, 2026 in Denver, CO at The Westin Denver Downtown. The seminar is valuable for professionals involved in car repair and billing, offering insights and training for routine tasks and strategic decision-making.
Date: 04-08-2026
Effective Date: 04-08-2026
C-14766
Subject: Informational Circular, AAR Field Manual Appendix D Update – April 1, 2026
Summary: Appendix D of the Association of American Railroads (AAR) Field Manual has been updated and is now available on the Railinc website. The appendix provides a listing of job codes and data elements used for repairs to Tank Cars and Covered Hopper Cars not included in standard AAR job codes, aiming to provide uniform and accurate data reporting for estimating, billing, auditing, and analysis.
Date: 04-13-2026
Effective Date: 04-01-2026
C-14777
Subject: Informational Circular, INTX Marked Cars – DELAYED to June 1, 2026
Summary: Circular letter C-14745 was issued on February 17, 2026 notifying the industry of the intent to create an Equipment Advisory for all INTX marked cars on May 1, 2026. Based on comments received from the industry, this date has been pushed back to June 1, 2026, and the Equipment Advisory will be created on May 1, 2026 for all cars in Umler with the INTX mark.
Date: 04-20-2026
Effective Date: 04-20-2026
C-14780
Subject: Informational Circular, Revision to Office Manual Rule 112.A.3.a, Group Billable List
Summary: In March 2026, the Arbitration & Rules Committee reviewed and approved a proposal advanced by the Car Repair Billing Committee to update the Office Manual Rule 112 Group Billable list. The change involves the proposed Office Manual Rule 112.A.3.a regarding job codes of repairs applying only to the same car and will be included in the July 1, 2026 release of the Office Manual.
Date: 04-22-2026
Effective Date: 07-01-2026
Greenbrier’s Regulatory Services Group
Peace of mind for your business.
Led by Diana Aylward, Greenbrier’s Regulatory Management Group provides regulatory, engineering, process consulting and advocacy support to the railcar repair industry and the petrochemical rail shipper community.
Our core services include:
- DOT Compliance Assessments (Corporate and Plant)
- DOT Hazardous Materials Training (Corporate and Plant)
- Federal Claims Mitigation Support (e.g., FRA and PHMSA)
- Regulatory Counsel and Policy Advocacy
- Railcar Repair Management (Design Review, Drawings, Engineering and AAR Approval Administration)
- Tank Car Reliability & Maintenance Programs (per 49 CFR Subpart F of Part 180)
- Tank Car Maintenance Data Collection & Performance Analysis
For inquiries about these summaries or any of our services, please reach out to: regulatoryservices@gbrx.com
About Greenbrier Management Services (GMS)
Greenbrier Management Services (GMS) is North America’s most comprehensive railcar management solutions provider. GMS manages nearly 400,000 railcars and has invested over 20 years in developing technology, processes, and people to provide the best railcar management products and services in the industry. GMS is powered by proprietary software and the best subject matter experts in the railcar business.
COMPREHENSIVE. INTEGRATED. VALUE.
Combined, these two vitally important capabilities are able to deliver world-class solutions to every type of customer, from Class I railroads, lessors and industrial shippers to financial investors. GMS brings broad expertise to cover nearly any railcar management need that customers may have and its integrated solutions and reporting can be customized for any customer function or management need.