A SPEEDING car rammed a concrete divider and somersaulted at an exit of the Aberdeen Tunnel, killing the driver and four passengers. Coroner Warner Banks heard that the driver, Chiu Yuk-man, 42, had consumed beer with his friends in a Causeway Bay karaoke bar several hours before he died. The accident has sparked calls from a traffic engineering expert for blood-alcohol legislation to help stem motorists from driving under the influence of alcohol. ''It is a pity that there is no such legislation in Hong Kong,'' said B. S. Craddock, Senior Traffic Engineer of the Transport Department. A jury returned a verdict of death by misadventure on Chiu, who died of multiple injuries on May 23. Although a government chemist's report had shown a high level of alcohol in Chiu's blood, the jurors contended that there was insufficient evidence to show that the accident was caused by Chiu's speeding and consumption of alcohol. However, the jury conceded that the high blood-alcohol level might have impeded his control over the car. Chiu's colleagues, Lee Kwok-keung, 29, Tsang Kwong-wing, 30, and Wong Tsz-yin, 18, also died at the scene. A fourth passenger, Wong Yiu-hung, 28, died from his injuries 13 days later at Queen Mary Hospital. The jury returned verdicts of death by accident on Lee, Tsang and the two Wongs. The court heard that Chiu, Lee, Tsang and Wong Yiu-hung were drivers at a local cake shop. The only female victim, Wong Tsz-yin, was a clerk at the shop. Chan Kam-wah, a staff member at the tunnel who saw the accident, said the car was moving at a speed which greatly exceeded the limit of 50 km/h. He heard the noise of braking and saw the car hitting a bollard at the tunnel's Happy Valley exit. ''The car somersaulted . . . and landed on another bollard,'' he said. Mr Craddock said the general lane signalling and control of the tunnel was excellent, adding that the low accident rate confirmed that drivers had no difficulty in understanding the arrangement. But he said drivers could easily miss the speed limit signs which were placed at the entrances to the tunnel. There were insufficient signs to indicate that the speed limit had been lowered by 20 kms to 50 km/h during a single-tube, dual-carriageway operation. He suggested that illuminated speed limit signs should be installed in the tunnel.