AN accident at the age of three wrecked Cheng Yan-keung's dream of becoming a sportsman, but 15 years later he has emerged as one of Hong Kong's top wheelchair athletes. ''I was hit by a runaway tractor outside my home in Enping county [in Guangdong]. I was told by my mother that the vehicle went out of control while negotiating a bend. ''I fell into coma and my parents were told by the doctors that I would never be able to stand again,'' said Yan-keung, a printing apprentice. Speaking with two other disabled team-mates also gearing up for the first wheelchair race in Ho Chi Minh City this month, Yan-keung believes a wheelchair race will help him achieve sporting excellence. ''I like sports and since I can't use my legs I think I can use a wheelchair to fulfil my dream as a sportsman,'' he said at the Hong Kong Sports Institute in Sha Tin yesterday. The race on January 15 - the second international event to be staged in Vietnam - is sponsored by Cathay Pacific Airways and the South China Morning Post. Yan-keung, Wong Chi-Keung, 26, and woman athlete Chan Kam-tim, 30, have added weightlifting in their preparation for the race in the past few months at the sports academy. ''We train for two hours here three times a week, and apart from doing weight-lifting to improve our strength, we roll our wheelchairs for 18 kilometres to and from Tai Po along the cycling track,'' Miss Chan, a government data processing operator, said. Experienced athlete Wong Chi-keung is perhaps Hong Kong's biggest hope of doing well in Vietnam, thanks to a new $20,000 tricycle from the United States. Mr Wong is a member of the sports institute's scholarship programme and is being trained regularly at the complex. Despite a high fever, Mr Wong finished second in Hanoi last January.