A two-week road trip from Portland, Me., to Los Angeles is underway to show the commercial viability of hydrogen-fueled vehicles.

Nine auto manufacturers, the U.S. Department of Energy, California Fuel Cell Partnership, the National Hydrogen Association, and the U.S. Department of Transportation are sponsoring the Hydrogen Road Tour.

"The technology necessary to put these cars on the road and keep them moving exists today," said Paul Brubaker of the U.S. DOT's Research and Innovative Technology Administration. "The question is not if hydrogen-powered vehicles will be available commercially, but when."

The tour will make 31 stops in 18 states. Hydrogen vehicles from BMW, Daimler, Ford, GM, Honda, Hyundai-Kia, Nissan, Toyota, and Volkswagen will be making the journey, and will be joined by hydrogen transit buses along the route.

For more details on the road tour and the current state of hydrogen-fuel technology, check out the article on C-Net.com