Since 2000, the Hong Kong Environmental Protection Department (EPD) has been working to reduce the greenhouse gas emissions derived from motor vehicle usage. With the high level of traffic congestion, dense highrise buildings, and diesel vehicle usage in Hong Kong, roadside levels of respirable suspended particulates (RSP) and nitrogen dioxide (NO2) often exceed air quality standards. The emissions control program’s main initiatives included:

• Adopting tighter fuel and vehicle emission standards
• Adopting cleaner alternatives to diesel vehicles where practicable
• Controlling emissions from the remaining diesels with devices that trap pollutants
• Strengthening vehicle emission inspections and enforcement against smoky vehicles
• Promoting better vehicle maintenance and eco-driving habits

The aim was to reduce RSPs by 80% and NO2 emissions by 30%. Since the program has started the Hong Kong EPD has gradually implemented more stringent vehicle emissions standards, while simultaneously providing grants to help individuals retrofit their vehicles to meet those new standards. Sales of higher sulfur content diesel fuels have also been restricted.

To address the fuel usage of the 6000 diesel fueled public light buses that drive in Hong Kong each day, a grant of up to $80,000 was given for each bus that was upgraded or replaced with a liquefied petroleum gas (LPG) or electric powered bus. Those that were not upgraded and still utilize diesel fuel were placed on a registry and are subject to a new tax program. Similar grant programs have been utilized for light and heavy diesel vehicles in Hong Kong, to help incentivize adoption of alternative fuel sources and other particulate reduction devices.

In order to enforce the new restrictions, the EPD stepped up inspection of vehicles by placing spotters out on the streets to pick out non-compliant vehicles for additional emissions testing. If the vehicle does not pass an emissions test within a specific period after being spotted, the vehicle’s license is revoked. New penalty tickets of $1,000 may also be assessed to the owner of the vehicle that fails an emissions test.

Since the implementation of these initiatives, roadside air quality has improved. Compared with 1999, the roadside concentrations of some of the major air pollutants have dropped in 2011: respirable suspended particulates (RSP), sulphur dioxide (SO2) and nitrogen oxides (NOx), have been down by 33%, 56% and 28% respectively, and the number of smoky vehicles spotted has also been reduced by about 80%. However, nitrogen dioxide (NO2) at the roadside has increased by 23% during the same period. The rise in roadside NO2 levels has resulted in an increase in the number of days with roadside air pollution index (API) reaching the “very high” level (API exceeding 100) in recent years. To address the continued NO2 increase, the EPD and the Hong Kong government are pushing forward with lower-emission retrofits of the five franchised bus company fleets and full reimbursement for fitting their buses with selective catalytic reduction devices.