An extra row of barriers may be added to high-risk areas along Tuen Mun Road to help prevent a repeat of last week's tragic accident which left 21 people dead after a bus plunged off the highway. Highways Department officials told a special meeting of the Legislative Council's transport panel that it was considering installing the barriers as a 'double layer of protection for vehicles' travelling on the highway. Legislators and government officials attending yesterday's meeting stood for a moment's silence in memory of the accident victims. The department has already pledged to install extra steel posts to help strengthen the existing barriers, known as parapets. A spokesman for the department, senior engineer Luk Wai-hung, said it would double the number of vertical posts holding up three horizontal crash barriers along some stretches of the highway. 'The posts were originally three metres apart, now they will be 1.5 metres apart. We will implement this first at the accident location, and then identify other high-risk areas,' Mr Luk said. The first phase would cost $200,000 to $300,000, he said. Mr Luk said rough calculations suggested the additional posts would double the strength of the barrier, although no detailed analysis had been done. 'We just want to do some immediate improvement work on the existing design of the parapets. This is easy to do and can be done fast,' he said. The department would install the posts 'as soon as possible'. While the accident is being investigated by the police and an independent three-man team led by Transport Advisory Committee chairman Cheng Hon-kwan, appointed by the government this week, the Highways Department has also launched an internal probe of parapet design, including the double-barrier design, Mr Luk said.