REUTERS: Hyundai's hydrogen fuel cell car hits the road in California.

  

South Korean auto-maker Hyundai says it has launched a new era of clean, hydrogen-fueled motoring in the US. In a high-profile ceremony on Tuesday, the company's first hydrogen fuel-cell car customer received the keys to his new Hyundai Tucson, although as Rob Muir reports, there are still challenges to be met before the technology becomes mainstream.