A?automatic suspended monorail system developed in Germany was introduced in Beijing Monday as an alternative to the traffic gridlock that clogs the streets and pollutes the air of China's major cities.

H-Bahn sky train at the Düsseldorf International Airport, Germany? [Düsseldorf International]

Lin Youling, president of the China Business Unit of Air Train International, which introduced the technology to China, said the "sky rails" will utilize the H-Bahn system, a suspended, driverless passenger monorail engineered by the Germany company Siemens.

The H-Bahn, or hanging railway technology, has been in use at the University of Dortmund, Germany since 1984 and at the Düsseldorf International Airport since 2002, but Siemens has not been actively marketing the system, and will no longer carry out turnkey projects.

Still, said Lin, Air Train International plans to build 20 to 30 sky trains in China within five years. The H-Bahn systems are designed to go about 50 kilometers (30 miles) an hour and to transport 75 passengers in each of its four cabins, Lin said.

The H-Bahn system runs on four electric DC traction motors that use direct current drawn from either a conductor rail or an overhead line. The main braking is done with a combined regenerative/rheostatic brake that feeds energy back into the power supply system.

Use of overhead railway lines may help ease traffic in some of China's densely populated cities, said Wang Mengshu, a professor at the Tunnel and Underground Engineering Research Center at Beijing Jiaotong University.

Professor Wang's comments were offered in a statement read at the Air Train International press conference in Beijing.

Wang, a member of the Chinese Academy of Engineering, said the newly proposed transport method costs less and take less time to build than subways.

"Many medium and small cities are not in a position where they can build subways, given their populations, GDPs and other factors," he said. "And even if they are allowed to build them, the cost of operating the subways will be huge."

The alternative solutions, he said, can often be built for less. The low cost of construction and maintenance of elevated rails also makes them an advantage, Wang said.

Also on Monday, construction began on a maglev train line between downtown Beijing and the mountainous Mentougou district to the west. Using Chinese technology, magnets will levitate a train above a track.

The new low-to-medium speed S1 Line is the first of its kind in the country, making China the second nation in the world to have such a line, said Chang Wensen, chief project manager of the line.

The maglev line is being built over the objections of residents living along the line, who are worried about exposure to electromagnetic radiation, the People's Daily newspaper reports.

Chang said the maglev line will not harm people living near the tracks or the environment, because earlier experiments showed the lower speed maglev train emits almost no radiation.

But Qi Fansan, a senior engineer with the Beijing National Railway Research and Design Institute of Signal and Communication who lives near the maglev line, worries that although tests have indicated it will be safe, the standards used for testing are different from European standards.

Qi told the People's Daily, "The radiation will be there, no matter how small they said it is, and its negative impact may show in one or two decades."