NMRA Standards and Recommended Practices

The NMRA uses four types of Technical Documents to present technical information.

Standard - 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 - NMRA Recommended Practices do not rise to the level of being a Standard, however, they provide details of of various topics that have been found to be the best for interchangability or operation of products.  Recommended Practices are not used in determining the qualification of a product when compliance certification is being judged.  Comments are generally made if the product is found outside the recommended practice.

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

Technical Instruction - NMRA Technical Instructions are documents that are used to provide Instructions on the use of a tool or a piece of equipment or software.

Documents released for Public Comment

New documents.  This document has completed it's designated public review period without comment.  It will be presented to the Board Of Directors for approval at the Atlanta meeting in March 2020.

10-2-2019  S - 9.1 Electrical Standards for Digital Command Control  (2019)


Recommended Practices

The RECOMMENDED PRACTICE category was established by the NMRA Board of Trustees in January 1957, to:

  • Specify the details of major components to improve design and function.
  • Promote maximum interchange between and within units.

RECOMMENDED PRACTICES are only less mandatory than STANDARDS by virtue of their slightly less critical subject matter and/or the fact that deviation for specific reasons is permissible.


Technical Notes, Reports, Information


These Standards and Recommended Practices are a publication of

Permission to reproduce this copyrighted publication in whole or in part may be obtained upon written application to the headquarters of the NMRA.

Repository for Specifications and Protocols from other Groups

This section is intended to provide a repository for specifications from other groups. These specifications are maintained by these other groups and are not necessarity reviewed or require approval of the NMRA Board of Directors. However, NMRA has recognized these specifications to be worthy of providing to NMRA membership.

Layout Control Specifications

CMRI, Computer Model Railroad Interface by Dr. Bruce Chubb, MMR


Module Recommended Practices

Free-Mo Specifications

The Free-Mo organization, www.free-mo.org, is composed of over 50 local groups throughout United States and Canada. This group maintains their own standards and recommended practices that are published on their website. Please follow the link above for more information.

Lionel Collectors Club of America (LCCA) FasTrack Modular Railroad (FMRR)

Through a joint effort the LCCA and Lionel L.L.C. created the first nationally recognized O-Gauge Modular Railroad Standard in 2012. Since that time many local organizations have adopted the FasTrack Modular Railroad standard, creating highly detailed, kid friendly, and interactive railroads.  The standard provides enough flexibility that large conventional or wirelessly controlled railroads can be created in oval, dog-bone, E, F, H, T, V, U, or W shapes with ease.

The LCCA maintains a series of recommended practices on their own website.

  Lionel Fastrack Modular Railroad Specification Manual

LCCA FMRR Coordinator's Email: "expert (at) lionelcollectors.org"

Updated 10/31/2019