Riding a bicycle in Hong Kong can be hazardous, especially when negotiating the traffic, hairpin bends and precipitous slopes of the Mid-Levels. So when four boys at St Paul's College in Bonham Road had to come up with an invention for the 41st Joint School Science Exhibition on the theme 'a new sports vision', their minds swiftly turned to the idea of a device to improve cycling safety. It took nine months to complete the prototype 'Speed - in Control' and rig it up on an old bicycle, but the end result was so impressive it scooped six trophies - including overall champion. Team member Ringo Tang Wing-lo, 17, now a freshman at University of Hong Kong, said: 'We all like to ride bicycles and two of us had accidents when we were young.' So the students came up with a system for automatically switching on the brakes when the bicycle's speed reaches a certain pre-set level. Their contraption involves a dynamo that automatically activates the brakes when the bicycle reaches a given speed to slow the cyclist down.