It's a bike! It's a car! It's an ... ELF bike?

Mark Stewart turns quite a few heads as he zips through the streets on his neon green ELF bike. With each pedal, his feet take turns sticking out from the bottom while a gentle motor hums in the background.

What he's driving looks like a cross between a bicycle and a car, the closest thing yet to Fred Flintstone's footmobile, only with solar panels and a futuristic shape.

It's a "green" option for today's commuters.

Stewart, a 65-year-old family therapist and school psychologist from Cambridge, Mass., took the summer off in order to drive his new ELF bike more than 1,200 miles on trails and roads using the East Coast Greenway, a bike and pedestrian trail that runs from Canada to Key West.

He began his journey by flying down to Durham, N.C., on July 15, and estimates that the entire trip will take about a month. He covered the first leg, from Durham, N.C. to Reston, Va., over roughly five days, 60 miles at a time.

The ELF can go up to 30 mph, combining pedal and electric power, and reach 20 mph on electric power alone.

Needless to say, he's getting lots of questions along the way.

"It reminds me of when I saw a Smart car the first time," said Joanne Bury as she emerged from her Reston condominium building to take a look at the vehicle. "This is incredible. What is it?"

Such attention, Stewart says, is par for the course.

"I don't mind though. I mean, I like that people want to talk about it," he said.

The ELF, or "Organic Transit Vehicle," can go for 1,800 miles on the energy equivalent of a gallon of gasoline. It does not require the insurance, repair, and car maintenance costs of the average vehicle. Besides the cost of the occasional new tire, the ELF runs completely off what it costs to charge its battery.

Stewart bought the ELF from Durham-based Organic Transit, which sells them for a base price of $5,000. He said he wanted to avoid the almost $1,000 delivery charge, so he decided to fly down to pick up the bike in person and learn how to operate it before taking the long trip back home.

"I spent three days in the shop hanging with the guys there and learning the vehicle," Stewart said. "This is just an unsupported solo trip up here in a vehicle that nobody else really knows."

Stewart's ELF is only about the 40th to come off the production line. While few bike shop workers have seen the contraption, the materials, such as the tires and pedals, are items on your average bicycle.

Organic Transit CEO Rob Cotter took technology from aircrafts, boats and bicycles and incorporated them into a "green" 130-pound vehicle.

"About 30 years ago I was working in the performance car industry working on Porsches and BMWs," Cotter said. "At the time the world record for a streamline bicycle was 55 mph by ground and I realize that those efficiencies are capable with one horsepower. I realized from a social, ethical and environmental standpoint that we're doing something drastically wrong."

He was consulting on bike-sharing technologies being considered for New York City's proposed program when he saw there was a market for his vehicle.

"A combination of environmental catastrophes, high fuel costs, climate change and a migration of people moving to the cities all combined for a trend of people looking for an automotive alternative. But not everyone can fit a bicycle into their daily life," Cotter said.

"Issues like weather, steep hills, lack of carrying capacity, falling over and safety concerns steer many away from bicycles. The ELF was designed to address those concerns, contribute to the rider's health, cost savings and lessen their environmental impact," he said.

Demand has grown significantly, and Organic Transit has opened a second factory. The company is working on their 75th bike, with more than 200 already sold or reserved with a deposit.

"Right now we make them at a rate of one per day hand built in the U.S. but we're about to open up another facility on the West Coast to increase our efficiency sometime this year to get up to four per day," Cotter said.

While the ELF is classified as a bicycle by Organic Transit, the laws surrounding such a vehicle vary.

In the District of Columbia, where Stewart's GPS was taking him, the ELF is not allowed on the bike trails and paths. The city classifies it as a motorized bicycle.

"They can't operate the unit on a sidewalk, they can't park on a street, and they can't operate on off-street bike trails or bike routes," said Monica Hernandez of the city's Department of Transportation. "The only thing you can do (on the street) is stop to unload or load the unit."

The ELF would have to be parked off the street.

Stewart says so far he's only gotten looks of curiosity.

"A lot of cops have gone by me no one's said boo. They'll look, they're interested but they don't question its right to be on the road," Stewart said.

Associated Press writer Shaquille Brewster contributed to this report.