Honda has an auto in test with Fuel Cell/ compressed Hydrogen. For a few years now.
A lot of Canada's public transportation runs off Hydrogen.
Hydrogen burns off Heat & Water Vapors only! ( can't get cleaner than that)
After all, it is the most abundant element in the Universe!
As we know, not many Hydrogen filling stations around yet.
If you think about it, when Henry Ford built the the first auto here, there wasn't many Gas Stations around either.
My wife passed away 5 years ago at age 46 from MS.
She was 'Chronic Progressive" and all the drugs are for "Relapsing/Remitting".
She was on Beta- Seron for awhile way back. Along with a big monthly does on Solumedrol and Cytoxan to compress the lesions.