you can see the "Standards" for forklifts sold in the USA, at itsdf dot org, as long as you agree to not try and sell copies of what you download for free.
ITSDF is/should be the bible of forklifts, and are now the "keeper" of the B56.1 standard, which they took responsibility for, from the ASME, as it is the "Industrial Truck Standards Development Foundation".
Before ITSDF, ASME wanted to charge you something close to a private US college education for the ability to -look- at the standards, and it was always a great mystery as to what standards really were, for most people.