THE Government is considering incentives to encourage motorists to trade in their diesel-belching bangers for cleaner vehicles. It might even bring in tough legislation to reduce Hong Kong's alarming fuel emission levels. The Director of the Environment Protection Department (EPD), Dr Stuart Reed, said his department had drawn up proposals but would not release details until it had received feedback from other departments. They would include financial incentives for owners who swapped older vehicles for newer ones, he said. ''We need to move small vehicles away from diesel engines to petrol engines with catalytic converters,'' Dr Reed said. But even with Hong Kong's fast turnover of vehicles, it would take about 10 years to change all vehicles, he warned.