National Model Railroad Association

The National Model Railroad Association, Inc. ( NMRA ), the National Association of Model Railroaders in the USA. They regulated and standardizes the model railways in the United States.

Your office has the NMRA in Chattanooga (Tennessee).


According to the company, the NMRA was founded on 1 September 1935 in Milwaukee and registered on 17 May 1947 in Ohio as a non-profit organization to unify the former (typically incompatible ) systems of the manufacturers, so that products from different manufacturers can be used together could. The first publication dated the NMRA standards to the year 1936.


Include your goals

  • The standardization of model railway,
  • The advancement of consultation and cooperation among stakeholders
  • The promotion of personal skills,
  • Further training of model railroaders,
  • And the further development of the hobby.


In the normalization, the NMRA usually starts (abbreviated RP) so already to record existing standards and in the form of a Recommended Practice to be recorded. Mandatory standardized ( standardized ) characteristics of models are referred to as standard and abbreviated as " S" and a sequential number.

Examples of standards

The most well-known in Europe Recommended Practice should be the RP25, which defines the various types of wheel and wheel flange. The DCC protocol is defined in the U.S. as a recommendation for digital multi-train ( RP9 ).