Despite financial woes that threaten the automaker's survival, General Motors is continuing research on a fuel-cell electric vehicle, announcing that sometime this week one of the 100 Chevy Equinox FCEVs being driven in Los Angeles, New York and Washington, D.C., as part of Chevrolet's Project Driveway will drive the 500,000th zero-emissions mile of the real-world test program.

"This is a huge accomplishment, because we learn something about our vehicles, the hydrogen infrastructure and consumer acceptance of fuel-cell vehicles with every mile driven," Mary Beth Stanek, director of GM Fuel Cell Commercialization, said in a statement.

Fuel-cell cars and SUVs convert hydrogen and oxygen to electricity through an on-board electro-chemical reaction. The electricity is then used to power the vehicles' drive motors.

Stanek said candid feedback on "everything from the way the vehicle looks to technical input on brake 'feel' and performance to fueling experiences" has led to the resolution of several hundred customer issues.

The program has also provided Stanek and others associated with the Equinox with insight into how these vehicles are being used under real-world driving conditions, she said.

"We've been able to use these experiences to extend fuel-cell stack life and improve the regenerative braking system, which has already benefited our 2-mode hybrid vehicles since it's the same brake system used on the Saturn Vue, Chevy Tahoe and GMC Yukon 2-mode hybrids," she said.

No automaker is saying that it expects to make FCEVs available for purchase this side of 2020, but without programs such as Project Driveway they likely would never appear in a showroom.