The Airport Authority has bowed to pressure from green groups and agreed to carry out a social impact study on the planned third runway at Chek Lap Kok, as activists continue to snub meetings on the controversial project. But the airport operator has yet to specify what will be covered by the study, saying only that it will develop an approach "meaningful to local context and specific to the runway project". "We will devise the most appropriate method, looking at air, health or traffic congestion issues. We'll adopt the best world practice too," the authority's executive director of business development, Wilson Fung Wing-yip, said. Fung did not give a timetable but said he believed the voluntary study would be done in parallel with the statutory environmental impact assessment of the project, which involves 650 hectares of reclamation from the sea. Speaking to media yesterday, Fung said the social return on investment study carried out by the New Economics Foundation for the third runway at London's Heathrow Airport - to put a monetary value on such social costs as noise, air pollution and congestion - could not be directly copied. Instead, he said, approaches used by the World Bank or the European Union to assess transport projects might be more relevant. Fung also said it was "unfortunate" that none of the green groups invited to a meeting yesterday had shown up. "They wanted to know in advance the outcome of the meeting, though we have provided them with a large amount of information beforehand," he said, adding that the door to dialogue was still open. WWF Hong Kong director of conservation Dr Andy Cornish said, however, that the conservationists had very clear demands for the study and the authority knew them well. "The ball is in the authority's court. They have to close the gap and regain the trust of green groups," he said. Cornish said a genuine social return on investment study should put emphasis on engaging those affected by asking people what was important to them. But he did welcome the authority's decision to assess the carbon emission of aircraft in order to seek accreditation by the Airports Council International by early next year. Melonie Chau Yuet-cheung, senior environmental affairs officer at Friends of the Earth, said the meeting was snubbed because the groups and the authority could not agree what to discuss. "We don't want the agenda set and dominated by the authority," she said. "We wanted to discuss the details of what a social impact study should be." Chau also asked whether the authority was using a delaying tactic by not committing to a clear timetable to complete the study. She would not rule out launching an unofficial social impact study with other groups.