Winding through rice paddies and lazily blowing its whistle along bubbly creeks, a two-car train in rural northern Japan is the latest entrant in the battle against global warming. Following its runaway success with hybrid cars, Japan is bringing the world hybrid trains. Regular passenger runs are set to begin Tuesday on a short mountain route, the first time a diesel-electric hybrid train will be put into commercial service. "It's part of our efforts to be green," Yasuaki Kikuchi, a spokesman for East Japan Railway Co., said Friday during an exclusive trial run for The Associated Press. Compared to cars, trains are a relatively small contributor to global warming. In the United States, railways contribute just 4 percent of transportation-related emissions of carbon dioxide, the main greenhouse gas blamed for global warming. But the popularity of hybrid cars, such as Toyota Motor Corp.'s best-selling Prius, is helping to boost interest in hybrid trains. Railway companies around the world, including America's Amtrak and Germany's Deutsche Bahn AG, are working on or investigating the technology. Cost remains a hurdle. The Japanese train, which boosts fuel efficiency by 20 percent and reduces emissions by up to 60 percent, runs nearly 200 million yen (US$1.7 million), twice as much as a standard train, Kikuchi said. The Kiha E200, as it is known, is equipped with a diesel engine, two electric motors under each of its cars and lithium ion batteries on the roof. With the word "hybrid" splashed in silver across its side, the otherwise normal-looking train rolls quietly out of Nakagomi station, powered by its four electric motors. The diesel engine only kicks in with a rumble when needed to climb a hill or if the batteries run low. The batteries are recharged when the train slows down. After the power is switched off, the motors continue to turn for a while, and that energy - wasted in a non-hybrid train - is used to recharge the batteries. Besides the usual buttons and dials, the conductor also has a touch-panel monitor. Arrows show which way energy is flowing, connecting boxes that represent the engine, generator, motor and battery, busily changing direction every few minutes. Whether cars or trains, hybrids delicately balance the two sources of power, relying on a computer to minimize waste. The Kiha E200, which seats 46 and can hold 117 people including standees, is debuting on a line that runs about once an hour on a 79 kilometer (49 mile) route through a mountain resort area. East Japan Railway will gather data on fuel consumption, which is expected to vary with different passenger loads; maintenance needs and whether the power holds up for heating in winter, said company engineer Mitsuyoshi Yokota. In North America, Railpower Technologies Corp. has developed a hybrid train called the Green Goat for moving freight cars in a rail yard. But industry efforts are focused on developing cleaner fuels for non-hybrid trains, said Allen Schaeffer, executive director of the Diesel Technology Forum, a trade association representing engine and equipment manufacturers. "Here in the US, we're not really looking at hybrid technology as replacing the main locomotive," he said. Hybrid trains, long viewed as impracticable because it's cumbersome to get the various parts to work together, are catching on thanks to hybrid cars, said Makoto Arisawa, an ecology professor and train expert at Keio University in Tokyo. "Maybe we can't expect too much from a railway this small," he said. "For the technology to be effective, it must become more widespread." That didn't stop Hitomi Shimizu, 29, who runs a nearby inn, from showing up at Nakagomi station to get a snapshot of herself on the platform with the train. "I'm so proud of being part of a community with a train that's gentle to the environment," she said.