Standards & Recommended Practices

The S Scale SIG endorses the standards recognized by the NMRA and NASG for S Scale trains and encourages S Scale manufacturers and modelers to build to those standards.

What is a standard or recommended practice?

The NMRA defines standards and recommended practices in this way:

A Standard is a figure, relationship or dimension that is mandatory, it is “cut in stone” so to speak and must be followed to facilitate interchange or interface, whichever the case may be. Standards can be changed from time to time but ONLY by the vote of the NMRA membership after proper policy procedures have been followed and the membership has been fully informed.

RPs (Recommended Practices) are those figures, relationships or dimensions that the Engineering Committee has established through actual tests and feel are beneficial to operation. These are not required to be voted by the membership except when in a package such as the Module Standards and RPs. These are presented to the Board of Trustees (BOT) for their study and approval.

Standards for modeling at 1:64

(A complete listing of NMRA standards may be found at

1:64 Specific Recommended Practices

(A complete listing of NMRA recommended practices may be found at