At this time, there is not one unified industry standard that is recognized for tiny homes on wheels and each jurisdiction, bank, insurance agency, etc… could have a different definition and requirements, including size and if they are allowed as a dwelling.
Most tiny home builders are building RVs built to the NFPA 1192 Standard or the Park Model Standard, ANSI A119.5 for the ability to have them certified and registered, to get a Vin number and title.
These standards address all safe health, life, and fire precautions.
The builders most always exceed the minimum requirements of these standards and build to 2 X 4 and 2 X 6 construction, increase insulation values, have 25-year roof warranties, increase truss loads when applicable, and use superior quality materials.
The beauty of tiny homes is they are custom built to order and can be built for all seasons with a focus on durability and longevity. They can also be built to any added requirements of the jurisdiction.
Certification