SHANGHAI'S 16-kilometre underground Metro Line One, linking the north and south of Puxi, goes into full operation today to alleviate congestion on the city's limited and narrow roads. Line One, which took about five years to complete, will allow thousands of people to change from the dusty old public buses that up to now have been the principal form of public transport in the city. Line One's daily passenger capacity will be 370,000 and is expected to increase as train intervals become more frequent. But much is still to be done. The director of the Shanghai City Comprehensive Transportation Planning Institute, Gu Xianrong has proposed that special viaducts be constructed across the city to run trolley buses at fraction of the cost of alternative rail systems. He said the proposal was for a 600-kilometre six-line network, with three lines running north and south, and three cutting from east to west across the city. 'Each line will be two carriages wide and could be finished in two years. They will have an hourly passenger capacity of 30,000,' he said. That does not mean remaining plans for six underground lines and the six-line light rail system would be shelved indefinitely. The first phase of Metro Line Two will link Jingan Temple in Puxi and Longdong Road near Zhangjiang High-tech Park in Pudong. Construction will begin this year and it is scheduled for completion by 1998. But Mr Gu said the trolley-bus viaduct network would be a quicker partial solution to the traffic problem and give the Shanghai municipal government a breather as it continued to solicit and raise funds for the rail lines. Each kilometre of the metro line cost 700 million yuan (about HK$642 million) to build; the light light-rail line in comparison would be 250 million yuan. The viaduct would cost 50 million yuan for each kilometre. Mr Gu stressed that the two systems should run alongside each other for an efficient traffic network for Shanghai. He said one was a strong multi-storey road system, including flyovers for vehicles, and the other was the 400-kilometre railway system (including underground) for passenger transport. 'But construction of the rail system not only costs a lot of money, it takes a much longer time to complete,' he said. Mr Gu said viaducts for trolley buses were feasible alternatives while Shanghai made the transition to a market economy. 'And when we have the means, the viaducts can be laid with rail tracks to become a rail system,' Mr Gu said. Last December, an inner ring road was opened to vehicles in the area of Puxi and Pudong, cutting traffic congestion in the area by 17 per cent. As the inner ring road network will be expanded in the next two years, the population within the areas of the network is expected to drop from five million to two million. The residents will be moved as their old houses give way to viaducts and roads. Construction of two viaducts joining the inner ring road network has started. One joining Hongqiao airport in the west to the Bund along the Huangpu River will be completed at the end of next year. The Chengdu viaduct, from north to south, should be completed by the end of this year. An outer ring road to ease traffic out of city districts is also in being planned and will be completed by 2000. Mr Gu said these plans, coupled with efficient traffic management, were seen as vital to improving the traffic system. 'Roads in Shanghai are already few. Now there are only three square metres of road space for every resident, but the aim to increase that to 10 square metres.'