BURNABY, B.C. (CP) _ With the Hydrogen Highway still largely a dream outside California, Ford Motor Co. sees plug-in hybrid fuel-cell cars as a transitional step, says one of the automaker's top engineers in the field.

People ultimately will demand fuel-cell vehicles that provide the same performance and flexibility as conventional autos powered by internal-combustion engines, says Mujeeb Ijaz, Ford's manager of fuel-cell vehicle engineering in Dearborn, Mich.

``You need to do all the requirements, including towing of trailers and boats and having the utility of a normal engine,'' he says.

But the duty cycle of conventional engines _ lots of idling and hard acceleration under load _ drastically cuts the lifespan of fuel cells at their current state of development.

So-called mild hybrids, whose fuel cells work like current hybrid cars to provide peak power, will eventually arrive.

But plug-in hybrids offer an elegant interim solution to getting people into fuel-cell vehicles, providing something close to normal range and a lifespan similar to normal engines.

``So I think that's a second type of market, maybe the first commercially viable market because it's got the greatest pull from the customer's point of view,'' he says.

Plug-in hybrids _ fuel-cell or not _ are all the rage in green automotive circles.

The current crop of hybrids such as Ford's Escape SUV and Toyota's Prius sedan mate a small electric motor and battery pack to a conventional engine layout to provide either around-town electric drive or a kind of turbo boost to the gas motor.

Plug-in hybrids are essentially full-time electric vehicles that use a small conventional engine recharge a larger battery pack, drastically reducing emissions.

Substitute a fuel-cell for the internal-combustion engine and suddenly it becomes a pure zero-emission vehicle.

Fuel cells put hydrogen and air through a catalyst to produce electricity, with only heat and water as byproducts.

Ijaz says fuel cells are a good fit for plug-in hybrids because recharging the battery pack means running the fuel cell at a steady rate _ not the performance peaks and valleys produced when actually driving the car.

And as the name implies, the vehicle can also be plugged into the owner's house power to recharge its batteries at night.

``The fuel cell acts only as a backup power supply on the vehicle,'' he says. ``It comes on when you need it to extend your range.

``But if you don't need it to extend your range you just keep driving the vehicle, plugging it in and running it as an electric car.''

With only a handful of hydrogen refuelling stations in California and no publicly accessible ones yet in British Columbia, Ijaz says plug-ins offer a way to get at least light-duty fuel-cell vehicles on the road sooner.

Sabina Russell, research and development project manager at Ballard Power Systems' bus and automobile division, says fuel cells and batteries complement each other.

``We see this as having a potential to accelerate the commercialization of automotive fuel cells,'' she says.

Ford (NYSE:F) is showing off its HySeries plug-in hybrid prototype, based on its newest Edge crossover SUV, here this week as California Gov. Arnold Schwarzenegger visits Vancouver to promote the Hydrogen Highway initiative.

The Edge, which was driven here from Seattle, can travel its first 40 kilometres a day on battery power alone. It has a total range of 360 kilometres when the Ballard (TSX:BLD) fuel cell kicks in _ still short of the 480 kilometres considered competitive with conventional vehicles.

Ford says the Edge HySeries delivers gasoline-equivalent fuel city/highway economy of 5.9 litres per 100 kilometres with zero emissions, and as little as three litres if the vehicle is driven less than 80 kilometres a day.

The HySeries frame under its Edge bodywork looks like a giant capital I with a long cylindrical hydrogen tank lying inside it. A lithium-ion battery pack and fuel cell hang off the sides and there are electric-drive units at either end.

Driving the Edge HySeries underscores how far fuel-cell cars have come from earlier lurching and wheezing prototypes.

It operates silently with only a little electric-motor whine under hard acceleration.

But while the Edge looks showroom ready, it isn't.

Ford and its partner Ballard fall in line with its other competitors in forecasting fuel-cell cars will begin hitting dealers in the latter half of the next decade.

Large demonstration fleets in the hands of government and corporate users will be on the road before then.

``We have two critical steps that we have to get through that we currently haven't accomplished,'' says Ijaz.

``One is we identify the right design that we're going to commercialize and then we need to get the suppliers of that correct design lined up to build the factories that are necessary to start ramping up volume and bringing the cost down.''

Engineers are getting the upper hand on factors such as durability, range and cold-weather starting, said Ijaz.

``We're no longer at the point where we fear the technology is incapable,'' he says.

``But now we have to work on cost and so cost is the next main hurdle that we have to get over.''