THE Housing Authority has agreed to pay half the cost of installing security measures in Tuen Mun housing estates if residents pay the rest. The measures will include closed-circuit television, entrance gates and security guards on round-the-clock duty. Tuen Mun District Board member Chan Wing-sang said questionnaires handed out to more than 10 housing estates showed 100 per cent of respondents wanted security to be strengthened following a series of violent rapes and murders on women in the area. After a meeting with Tuen Mun, Tsing Yi and Sha Tin residents yesterday, a Housing Authority spokesman confirmed they would install security in two Tsing Yi housing estates for three months to see if the crime rate dropped significantly. But only 20 per cent of respondents supported the idea of paying half the expense as it would add an extra $80 to their monthly budgets. Mr Chan said there would be some relief for those with financial difficulties. ''The residents can pay for the security over five years. So, for the two buildings going to be modified, each apartment will pay $50 to $60 more for every month. ''For those who really can't afford to pay the extra money, the HA will transfer the case to the Social Welfare Department for an extra subsidy. And if the Department does not accept the case, the HA will let the families enjoy the facilities free of charge according to their situation,'' he said. Under this proposal, the new residents can also choose to move into other buildings if they do not want to pay a higher rent.