The United States Federal Transit Administration has released a report which reviews more than 20 hydrogen bus trials and demonstrations which operated worldwide between 2002 and 2007.  The trials were in the US, Europe, China, Japan and Australia.  Both internal combustion and fuel cell powered buses were trialled, as well as various fuelling and associated technologies. The resulting report analyses lessons learnt from the demonstrations, identifies key remaining challenges for introduction of the technology, and suggests potential roles for government in supporting commercialisation of fuel cell buses. The report can be downloaded here