Over the course of the trip the three vehicles covered 706.5 miles and consumed 28.8 kg of hydrogen. That works out to an average of 73.6 miles / kg. One kg of hydrogen has roughly the energy equivalent of one gallon of gasoline, so the mileage works out to about 73-74 mpg.
The drive was organized by the Japan Hydrogen and Fuel cell project. While all three of the automakers are developing plug-in battery electric vehicles, all three also continue to work on fuel cells. Both Toyota and Honda maintain that they feel hydrogen remains the best long term solution for full function vehicles.
[Source: Japan Hydrogen and Fuel Cell project]