A Beijing official voiced concerns over the widely applauded elevated high-speed bus, which has sparked fervent media reports worldwide as an innovative alternative to ease traffic jams.

"A feasibility research report on the bus hasn't been done yet. The project cannot be initiated until a model bus is produced, which will provide detailed technical specifications instead of just an idea," Zhang Wenbo, the head of the science and technology commission of Mentougou district, told the Global Times last week.

The so-called 'straddle bus' will allow other vehicles to move freely through the bus' hollowed out lower half.

Mentougou, which is planning a world's largest eco-city, will test run the bus over a six-kilometer-long section of road. If the test is successful, another 120 kilometers will be put in place.

Song Youzhou, a designer of the bus, said that the Philippines wanted to order 10 buses, India will talk with him in September, a US company will sign an agreement of intent soon, and the Argentinean government has also showed interest.

The bus drew public attention because it doesn't occupy road, which is already jammed with vehicles, and it runs exclusively on municipal electricity and solar power. The bus can hold 1,200 to 1,400 passengers with four to five passenger compartments, each compartment 10 meters long.

Zhang said the bus is in line with the eco-city's green transportation concept, but the commission is also considering other eco-friendly traffic patterns.

"It might be difficult for drivers to get used to driving under a moving tunnel. If we only run the bus on a dedicated traffic lane, we will have to change the current traffic system for it to operate well at intersections of the two different systems," Zhang said.

He said the public and media are hyping the new invention, adding the period from an idea to a product takes several years. "I cannot predict whether Mentougou, or another city or country would use the bus first. Some officials in China might not actually get the jump on the project because they might be unaware of the straddle bus despite extensive media reports."