Helpful Links

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Here is an online calculator to go between real life measurements and scale measurements: 

http://www.gardenstatecentral.com/scale_calc.html

AAR Railroad Reporting Marks:

https://www.railserve.com/aar_railroad_reporting_marks.html

 National Model Railroad Association:

 National Model Railroad Association (nmra.org) 

NMRA T-Trak Guidelines

 Considerations for T-trak Modules & Layouts 

HO Car Weight Chart