The fleet added a million miles in the last year, suggesting the hydrogen-powered crossover is growing in popularity.

Hyundai is celebrating another milestone for its Tucson Fuel Cell, reaching a collective 1.5 million miles across the whole California-based fleet.The hydrogen-powered crossovers surpassed a half million miles a little more than a year ago, representing the first year of US availability. The latest figure points to an increased rate of growth, however the overall numbers pale in comparison to traditional powertrains.

"Breaking the one-point-five million mile consumer mileage barrier gives us greater vision into the unlimited zero-emissions potential for Hyundai's fuel cell vehicles," says Hyundai Motor America product planning VP Mike O'Brien.

The Korean automaker claims the Tucson FCV was the first mass-produced hydrogen-powered vehicle to go on sale in the US. With total sales of just 125 units, each vehicle has an average of just 12,000 miles on the odometer after three years of availability.

US drivers average more than 13,000 miles per year, apparently confirming that the Tucson FCV is filling a small niche role as a second or third vehicle. Refueling may have been difficult for early adopters, with less than two dozen open retail stations currently spread across the entire state of California.

The diminutive sales numbers highlight the ongoing struggle for hydrogen powertrains as the technology faces ever increasing competitive pressure from battery-powered electric vehicles.