The Airport Express recorded 24 million passenger trips last year, six million short of the forecast the government made before its construction, an official paper revealed yesterday. While the forecast estimated 66 per cent of the passengers using the airport rail last year would be overseas visitors, the actual figure was 58 per cent. In a written reply to the Legislative Council, the Secretary for Environment, Transport and Works Sarah Liao Sau-tung attributed the rail line's lower than expected passenger numbers to changing conditions. She wrote: 'Some of the assumptions made then are different from the actual situation. The differences may be attributable to the rail's lower than forecast patronage.' The passenger forecast was made in the New Airport Master Plan in 1991. It made a number of assumptions, such as that there would be no competition from buses; more than 60 per cent of overseas visitors would use the rail line; and there would be congestion on the North Lantau Expressway. There are now 37 franchised bus routes connecting the airport and the rest of Hong Kong. And while the Airport Express charges between $60 and $100 for a single journey, the bus fares range from $3.50 to $45. Bus companies have 45 per cent of the market share, while the rail line has only 29.2 per cent. The government study estimated the expressway's two-way traffic flow at peak hours would reach 13,900 cars, prompting people to use the train to save time. The assumed congestion did not happen. The expressway's two-way traffic in peak hours last year amounted to only 4,800 cars. Dr Liao made no prediction as to when the passenger numbers that had been forecast for the Airport Express would be reached. She said the Airport Authority last year had commissioned a consultant to survey the market share between the rail line and other transport options.