NMRA Standards and Recommended Practices

The NMRA uses five types of Technical Documents to present information.

The NMRA, in its standards and recommended practices, addresses only the specific standards and recommended practices for model railroads.  These standards and recommended practices do not address any legal requirements.  It is the responsibility of the manufacturer to determine if their product conforms to all applicable governmental laws and regulations.

Standard (S) - NMRA Standards are to establish the broadest correlated set of limiting dimensions, electrical parameters and communications parameters within which interchange may be assured. 

Recommended Practice (RP) - NMRA Recommended Practices are only less manditory than Standards by virtue of their slightly less critical subject matter with respect to interchange and/or the fact that deviation for specific reasons is permissable. Recommended Practices provide details of various topics that have been found to be the best for interchangeability or operation of products.  

Technical Note (TN) - NMRA Technical Notes supplement the Standards to provide additional guidance on a given subject. 


Technical Information (TI) - NMRA Technical Information are documents that are used to provide information associated with a Standard or Recommended Practice.  

Technical References (TR) - NMRA Technical References are, for the most part, internal documents that provide a history of action taken in the Standards and Conformance Department.  

Legal Notices and Disclaimers

Legal Notices and Disclaimers for the use of NMRA Standards, Recommended Practices, Technical Notes, Techincal Information, and Technical Reference documents are available at this link:  Legal Notices and Disclaimers.

Standards (S)

Recommended Practices (RP)


Technical Notes (TN), Technical Information (TI) and Technical References (TR)

Technical Notes

Technical In formation

Technical References

NMRA Standards documents are copyrighted by NMRA under US and international copyright laws. They are made available by NMRA and are adopted for a wide variety of both public and private uses. These include both use, by reference, in laws and regulations, and use in private self-regulation, standardization, and the promotion of modeling, structural and engineering practices and methods. By making NMRA Standards documents available for use and adoption by public authorities and private users, NMRA does not waive any rights in copyright to the NMRA Standards documents. Permission to reproduce this copyrighted publication in whole or in part may be obtained upon written application to the headquarters of the NMRA.

Module Standards (MS)

Module Recommended Practices (MRP)

Updated 06-February-2024