Perhaps a working group could be established. These two steps are big ones, taken in a couple of years time. Buy-in should be obtained from national and international organizations that already exist. An overarching organization could monitor development of a harmonized system, those present being good potential members. Partnering with critical stakeholder institutions will help ensure success.
Transportation exists because needs emanate from all other activity sectors.
There must be a worldwide willingness to commit to data harmonization in general, because of the interdependency of all data, transportation included. All current collectors of information are good potential partners. We could build from international-scope transportation organizations already engaged in harmonization efforts. It would also be beneficial to bring in other categories of representation beyond transportation.