The Chicago Transit Authority (CTA) successfully operated three zero-emission fuel cell buses in a demonstration project to test the viability of the technology in heavy urban use.

Currently high costs and the lack of a fueling infrastructure are the largest obstacles mobile fuel cell technologies must overcome. Engineering challenges include reducing the size and weight of the unit to levels appropriate for vehicles. The use of gasoline as a fuel would greatly increase the prospects for fuel cells, but current reformers require very low, virtually zero sulfur gasoline.