POLICE expect trouble when they begin turning people away from the Lan Kwai Fong nightclub area in Central on Halloween and are appealing for the public to go elsewhere. Numbers will be strictly limited to prevent a repeat of the New Year's Eve tragedy in which 21 people lost their lives. Barriers and a strong police presence will effectively seal off the area around D'Aguilar Street, Wellington Street and Lan Kwai Fong itself. About 120 officers, with more on standby, will limit access to about 5,000, a quarter of the estimated number in the area on New Year's Eve. But district commander Chief Superintendent Cheung Chi-shum said he believed many people, especially those under the influence of alcohol, could start causing trouble when turned away on the night of October 31. ''We would be failing in our duty if we did not encourage people to stay away from Lan Kwai Fong this Halloween,'' he said. ''I think there will be trouble, but we will be prepared. I expect members of the public to be considerate. ''There will be stringent crowd control and I want to appeal to the public not to go to Lan Kwai Fong.'' Mr Cheung said the decision on exactly how many people would be allowed into the area would be taken by an officer in charge on the night. Two observation posts and one command post will be set up and two Auxiliary Medical Service teams and a doctor will be there. Hospitals and the Civil Aid Service will be on alert. The police were criticised after the New Year's Eve tragedy when it was revealed Central and Western district board members warned them of possible trouble following scuffles during last year's Halloween celebrations. Business in Lan Kwai Fong had picked up again after a dramatic fall-off immediately after the tragedy, said Mr Cheung. ''I think people didn't want to go there for sentimental reasons and relive the tragedy again. It seems to have picked up again now.''