A friend of mine is driving a concept fuel cell tractor trailer for his company. They had to add a digitized noisemaker to sound like a diesel engine because the truck is so quiet. Since the truck is so quiet, it's almost a safety hazard because it kind of creeps up quietly. He loves the fuel cell truck as it outperforms the diesel, it's quiet, and the range he gets is equivalent to 14mpg. My buddy said that they'll have to pry this truck out of his cold dead hands.