DETROIT — Hydrogen fuel cell cars could one day challenge electric cars in the race for pollution-free roads — but only if more stations are built to fuel them.

Honda, Toyota and Hyundai have leased a few hundred fuel cell vehicles over the past three years, and expect to lease well over 1,000 this year. But for now, those leases are limited to California, which is home to most of the 34 public hydrogen fueling stations in the U.S.

Undaunted, automakers are investing heavily in the technology. General Motors recently supplied the U.S. Army with a fuel cell pickup, and GM and Honda are collaborating on a fuel cell system due out by 2020. Hyundai will introduce a longer-range fuel cell SUV next year.

“We’ve clearly left the science project stage and the technology is viable,” said Charles Freese, who heads GM’s fuel cell business.

Like pure electric cars, fuel cell cars run quietly and emission-free. But they have some big advantages. Fuel cell cars can be refueled as quickly as gasoline-powered cars. By contrast, it takes nine hours to fully recharge an all-electric Chevrolet Bolt using a 240-volt home charger. Fuel cells cars can also travel further between fill-ups.

But getting those fill-ups presents the biggest obstacle. Fueling stations cost up to $2 million to build, so companies have been reluctant to build them unless more fuel cell cars are on the road. But automakers don’t want to build cars that consumers can’t fuel.

The U.S. Department of Energy lists just 34 public hydrogen fueling stations in the country; all but three are in California. By comparison, the U.S. has 15,703 public electric charging stations, which can be installed for a fraction of the cost of hydrogen stations. There are also millions of garages where owners can plug their cars in overnight.

As a result, U.S. consumers bought nearly 80,000 electric cars last year, but just 1,082 fuel cell vehicles, according to WardsAuto.

That’s why automakers will keep hedging their bets and offer electric vehicles alongside hydrogen ones.

Fuel cell cars create electricity to power the battery and motor by mixing hydrogen and oxygen in the specially treated plates that combine to form the fuel cell stack.

Advances in hydrogen storage, fuel cell stacks and batteries have allowed engineers to significantly shrink those components to fit neatly inside a sedan. Oxygen is now collected from the air through the grille, and hydrogen is stored in aluminum-lined, fuel tanks that automatically seal in an accident to prevent leaks. Reducing the amount of platinum used in the stack has made fuel cell cars less expensive.