WORRIED taxi drivers want to use outlawed two-way radios to call for help, amid fears of a serial robber targeting their vehicles. Taxi unions are unhappy with police proposals to boost safety and want direct communication with each other. But only licensed radios, used to call their company station, are legal under regulations set out by the Office of the Telecommunications Authority. Drivers are on the alert after police reports that a man 'with a Chairman Mao haircut' was believed to be behind a spate of robberies all involving a similar method. Kowloon Taxi Owners' Association chairman Yam Tai-ping said drivers were vulnerable. An extra radio to contact other drivers would help protect them. In a dangerous situation, they could be killed in the time it took to make a legal radio call to base. 'Authorities say these radios use low-frequency channels which might jam with those of the police or fire services,' Mr Yam said. 'We understand their concern but we want these radios to become a legitimate channel for drivers to help each other in emergencies.' Drivers were unable legally to refuse a fare, regardless of their suspicions over certain passengers. Mr Yam said taxi robbery cases were rising and becoming more brutal. 'People desperate for money will consider robbing taxis because it is the simplest thing to do - just wielding a knife,' Mr Yam said. Police figures show 301 reports of taxi robbery last year against 213 in 1994. More than 100 were reported in the first five months of this year and major black spots include remote new towns such as Yuen Long, Lau Fau Shan, Tseung Kwan O and Lei Muk Shue. Mr Yam said the true number was higher than police figures indicated. Wong Kit-hak, 18, was jailed for life last month for murdering part-time driver Cheung Chi-choi, 41, in September last year. The helpless driver had his head and hands bound with sticky tape when he was slashed seven times during a hold-up on a deserted Yuen Long hillside. One of the wounds severed his spinal cord. His body was dumped and not found for two days. Senior Inspector Henry Chiang Kwok-wah, of the Crime Prevention Bureau, said police were introducing a radio code system to fight the spate of assaults.