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Diesel vehicles emission is the main contributor to the air pollution in Hong Kong accounting for almost all the particulate and 75% of nitrogen oxides emissions from vehicles. The control strategy of the Hong Kong Environment Protection Department is: Introducing the most stringent practicable emissions and fuel standard. Introducing clean alternatives to reduce the reliance on diesel vehicles Strengthening the inspection on the emissions of motor vehicles Stepping up the enforcement against smoky vehicles Retrofitting of in-use vehicles with locally practicable technology Promoting environmentally friendly driving behavior and awareness of proper vehicle maintenance. This paper summarizes the progress of all the control measures and also reports in details the results and the way forward of the various trials of diesel vehicles retrofit technologies including small particulate traps, oxidation catalysts and ultra low sulphur diesel.

To abate the diesel vehicle emissions, Hong Kong Environmental Protection Department (HKEPD) has implemented comprehensive control measures including retrofitting programs for the pre-1995 light and heavy-duty diesel vehicles. Local franchised bus companies also carried out their own catalyst-retrofitting program in recent years as part of their emission control measures. Before launching the retrofitting programs, we carried out trials to investigate the application issues of exhaust after treatment technology under local operation conditions. Parameters such as diesel catalyst cell density, engine exhaust temperature, backpressure, diesel fuel sulphur content and in-use catalyst durability performance that form the key elements for retrofitting are studied. Also, the in-use catalyst monitoring performance by the use of carbon monoxide (CO) and hydrocarbon (HC) measurement at high idle and dynamometer testing is investigated.