The hydrogen fuel-cell vehicles being used in the pilot program are electric-powered, but use the hydrogen fuel to generate electricity instead of storing it in batteries like traditional electric vehicles (EVs). The EPA's Equinox will remain in their fleet for testing for the next six months at the agency's Washington, D.C. headquarters.
An array of on-board electronic devices will track and log performance data and real-world metrics to help GM advance its fuel-cell projects. The zero-emissions nature of the vehicle are what attracted the EPA to the deal, though it also has a history of cooperating with carmakers in testing new environmentally-conscious technologies.
It's not clear what source GM or the EPA is using for the hydrogen in the fuel-cell vehicles, but it is worth noting that the most common way of generating hydrogen involves the use of natural gas - a fossil fuel - and a fair amount of emissions, making the hydrogen fuel-cell vehicles not true zero-emissions vehicles, but rather zero tailpipe-emissions vehicles.