Talk about irony. I'm driving one of the world's most environmentally responsible cars into Las Vegas, the world capital of excess.

My ride is the HydroGen1, General Motors' zero-emission fuel-cell-powered development vehicle, and I'm taking it over for the last leg of a 230-mile endurance run dubbed Challenge Bibendum by organizer Michelin. Participating are a host of alternative-fuel vehicles, including nine fuel cell cars.