The government is planning to phase out old diesel vehicles to reduce roadside pollution, Secretary for the Environment Wong Kam-sing said on Thursday. Wong said one option that can be adopted from overseas and the mainland was to discontinue the licenses of diesel vehicles which have reached 15 years old. “We hope to draw up a retirement age [for these vehicles],” he said, adding that diesel vehicles contributed to 80 per cent of pollutants at roadsides. He said overseas authorities on one hand offered incentives to encourage owners to phase out diesel vehicles and on the other hand introducing a cap on their time in use. “We will discuss incentives with industry stakeholders, and see how to balance their business and Hong Kong’s air pollution,” he said. The environment minister spoke of the new initiative as roadside air pollution indices have reached the “very high” level of 100 in three busy districts in the past nine days. The Environmental Protection Department warns people with heart or respiratory illnesses against physical exertion and outdoor activities when the indices reach this level. Wong also said his bureau was now drawing up a target for reducing roadside pollution in 2015.