Undersecretary for Transport and Housing Yau Shing-mu told lawmakers on the transport panel yesterday that the underpass would have to be shorter, narrower and with only a few vending machines instead of the shops mentioned originally.

'We know that people would love to have spacious passages underground, lined with shops if possible,' Yau said. 'We also wanted to do that, but there are limitations because the streets in Causeway Bay are crowded with building foundations and underground shopping malls. We have had to adjust our expectation due to these technical problems.'

Yau said the scaled-down pedestrian subway would be six metres wide and extend from Victoria Park as far as Russell Street in Times Square. The original plan did not specify the width, but it gave the impression of relatively wide spaces as in Taiwanese and Japanese underground developments, with plentiful room for shops.

Democrat lawmaker Kam Nai-wai was disappointed to hear the subway would not reach Happy Valley. 'It was such a good idea that everyone loved it,' he said.

The subway must stop at Russell Street, Yau said, since the four routes leading to Happy Valley - Lee Garden Road, Percival Street, Matheson Street and Canal Road East - are unusable due to engineering constraints, and the traffic disruption and public nuisance construction would cause.

Matheson Street, which the government study found was the most desirable option, could accommodate a subway no wider than three metres, he said.

'We recommend that the construction of this section be held in abeyance pending redevelopment of the old buildings along the road to provide the necessary setback of construction for a six-metre-wide subway,' Yau said.

Tommy Cheung Yu-yan, vice-chairman of the pro-business Liberal Party, said the changes would make the subway too narrow and monotonous. 'You've just said there would be no shops,' he said. 'It will be a long and boring passage with only a few vendors scattered inside.' He feared few would use such a passageway.

Democrat legislator Andrew Cheng Kar-foo asked if the subway could be widened to 10-15 metres. 'Originally, many people who listened to the chief executive's words imagined the underground networks in Causeway Bay becoming like those in Japan and Taiwan, which are flooded with people and filled with many shops,' he said.

Yau replied that the government's original concept was to have spacious subways lined with shops and linked with shopping malls.

'But, after studies by Transport Department officials, we found many problems: the streets in Causeway Bay are so narrow and there are so many foundations and constructions underground,' he said. Detailed technical feasibility studies would be disclosed in mid-year, he said.

Professor Bernard Lim Wan-fung, from Chinese University's department of architecture, said the subway could be built wider than six metres. 'It may be a matter of cost. We could build the subway network a little bit deeper so that it can be wider.

'Yes, there is a limitation due to the foundations of buildings, but the area they take up would not be wider than the area those buildings occupy above ground.'

Lim, a Town Planning Board member, said the government should liaise with shopping malls to make their underground structures part of the subway.

'It is a miracle that we do not have any major incidents because of the crowding in Causeway Bay whenever there are functions in Victoria Park and Hong Kong Stadium,' he said.