The government has been warned that traffic conditions in Yau Tsim Mong district will worsen if it fails to push ahead with a proposed vehicle underpass beneath Austin Road. The work is seen as vital to divert traffic generated by the West Kowloon Cultural District and a high-speed rail line to Guangzhou which will have its terminus in West Kowloon. In a final attempt to stop lawmakers from passing the HK$66.9 billion rail project today, experts from Professional Commons, a lobby group, accused the government of hiding crucial figures that showed the link's possible traffic impact on its neighbouring districts. 'Suppose all the government's road improvements works can be carried out, 11 junctions would still only have marginal capacity, while two would have no capacity left,' Roland Taylor, an experienced engineer on MTR projects, said. According to a government-commissioned transport impact study obtained by the group, a crucial part of the improvement works included an underpass for vehicles under Austin Road that would connect West Kowloon and Tsim Sha Tsui. 'If this underpass cannot be finished when the link opens in 2015, the road network will not even be marginally sustainable by 2031,' said Paul Zimmerman, a member of the group. 'But the government has not started doing a feasibility study.' The proposed underpass was not included in the HK$11.5 billion set aside for non-rail-line facilities. An official from the Highways Department said, however, that they had already conducted a preliminary study and were satisfied the underpass was technically viable. He said it was not included in the plan because they did not yet know the design of the West Kowloon arts hub. 'Having big commercial centres in the hub would create a very different traffic volume from, say, like having a big piazza. We want to wait until the design draft is out to make a more accurate estimation.' Five years could be a bit tight for both consultation and construction of the underpass, given that many infrastructure projects - including the Central to Wan Chai bypass - have failed to be launched in over a decade. It is highly likely, though, that Legco's Finance Committee will pass the funding of the Guangzhou-Shenzhen-Hong Kong express link, as more than half of the 60 members have already expressed their support for the project. Tsoi Yuen Tsuen villagers, whose homes will be razed to make way for the railway, conservationists and activists have vowed to mobilise more than 1,000 protesters today. They plan to surround the Legco building when the meeting begins at 3pm. A group of students who began a vigil on Wednesday will continue walking around the building until the meeting starts.