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LCQ9: Emission and operational mode of public light buses

     Following is a question by the Hon Fred Li Wah-ming and a written reply by the Secretary for the Environment, Mr Edward Yau, at the Legislative Council meeting today (November 17):


     Many members of the transport trade have complained to me that there are serious defects in the braking, exhaust and fuel systems of the existing Euro IV and Euro V public light buses (PLBs).  These PLBs have to stop frequently for 20 to 45 minutes while travelling to perform a "carbon-burning" process.  This affects the working hours of the drivers and the quality of PLB services.  Besides, due to frequent mechanical failures of Euro IV PLBs, members of the trade are afraid of buying new ones.  As a result, many PLBs which are older than normal PLBs have to be used for extended periods.  The repair and maintenance costs of such PLBs are extremely high, and it is also difficult to achieve the Government's emission reduction targets.  In this connection, will the Government inform this Council:

(a) whether it knows the number of Euro commercial vehicles (from Pre-Euro models to Euro V models) in Hong Kong at present, as well as the ages in general, actual ages and service years upon retirement of such vehicles, and provide breakdowns of such figures by vehicle type;

(b) of the number of old PLBs replaced through the Government's grant scheme and the total amount of grants paid by the Government in the past three years;

(c) whether it has received complaints from the trade about the aforesaid problems of PLBs; if so, of the number and main contents of the complaints received in the past two years;

(d) of the number of PLBs which are older than normal PLBs and have to be used for extended periods; whether the authorities have assessed the impact of emissions from such PLBs on the air quality of Hong Kong; if so, of the details; if not, the reasons for that; and the Government's strategies to reduce such air pollution;

(e) when introducing Euro IV and Euro V PLBs into Hong Kong, whether the Government had conducted the relevant feasibility and technicality studies to ensure that these PLB models were suitable for operation in Hong Kong; if so, of the details; if not, the reasons for that; and

(f) of the levels of emissions from Euro IV and Euro V PLBs before and during the "carbon-burning" process, and how such levels of emissions compare with the current emission requirements for Euro IV and Euro V vehicles in Hong Kong?



     The operational mode of PLBs is different from that of the diesel light buses that have been used by the trade.  To meet Euro IV or more stringent particulates emission standards, light bus manufacturers have adopted diesel particulate filter (DPF) which is an advanced particulates emission reduction technology.  During the operation of the vehicle, the DPF not only collects the particulates, but also automatically burns off the particulates to achieve self-regeneration.  If excessive particulates are trapped in the DPF, the engine control system of the vehicle will send a signal to the driver for regeneration.  The driver should then stop the vehicle as soon as practicable and start the manual regeneration process to burn off the trapped particulates.  During the DPF regeneration process, there may be a slight seepage of diesel into the engine oil tank.  It takes some time for the light bus trade to get used to this new operational mode of the DPF.

     When the new generation of light buses was first introduced, some light buses required frequent manual regeneration of the DPFs and there was excessive seepage of diesel into the engine oil tank.  When the problems were brought to the notice of the Environmental Protection Department (EPD) in April 2008, it immediately followed up the issue with major light bus manufacturers' local authorised agents.  Tripartite meetings were held with relevant transport trade organisations and the authorised agents of the light buses for joint follow-up action.  The engineers of the manufacturers also came to Hong Kong promptly to understand the situation and work out a solution.  In April 2009, one of the major manufacturers improved the engine control units (ECUs) and solved the problems of excessive seepage of diesel into engine oil tank and frequent manual regeneration of the DPFs.  Newly ordered light buses are also equipped with the modified ECUs.  According to the manufacturer, so far no further complaint has been received from the trade.  In a meeting with light bus trade organisations in June 2009, the EPD noted that the problem had been handled properly.  According to the other supplier who only provides light buses to one operator, the problem was solved in early 2010.

     Our replies to the specific questions raised are as follows:

(a) We do not have information on the age profile of retired vehicles.  A breakdown of the average age and number of licensed vehicles by Euro standards in Hong Kong as at October 4, 2010 is shown in table 1 in the annex.

(b) The Government completed on March 31, 2010 a three-year grant scheme on replacement of pre-Euro and Euro I diesel commercial vehicles.  Under the scheme, a total of 328 pre-Euro and Euro I PLBs were replaced with new models.  Owners of 137 PLBs who had not completed the application procedures for the grant on time were allowed to retain their eligibility until March 31, 2011.  As at end-October 2010, a total of 431 light buses have been replaced with new models under the scheme, and the total amount of grant involved was $23.08 million.

(c) The light bus trade's complaints were mainly concerned with excessive seepage of diesel into the engine oil tank and frequent manual regeneration of the DPFs.  The complaints involved two light bus models.  According to light bus suppliers, less than 60 PLB complaints were received over the past two years.

(d) Vehicles have no fixed serviceable lifespan and we do not have statutory limit on vehicle age.  The law only requires that an in-use vehicle complies with the concerned emission and safety standards when renewing the vehicle licence.  In deciding to replace their vehicles, vehicle owners usually consider factors such as vehicle reliability, whether the concerned vehicles can meet their daily operational needs, maintenance expenses and financial considerations, etc.  Table 1 in the annex indicates that the average age of PLBs is generally lower than other commercial vehicles.

     Expediting the retirement of highly polluting diesel commercial vehicles, including light buses, will facilitate early improvement of roadside air quality.  Replacing pre-Euro, Euro I or Euro II vehicles by Euro IV models can reduce the emissions of particulates and nitrogen oxides by 87% to 97% and 50% to 61% respectively.  Therefore, the Government launched a 36-month grant scheme to encourage the early replacement of pre-Euro/Euro I and Euro II diesel commercial vehicles in 2007 and 2010 respectively.  We also consider that their early replacement cannot be expedited solely through the grant scheme.  As such, we proposed at the meeting of the Panel on Environmental Affairs of the Legislative Council on November 24, 2008 to consider introducing suitable disincentive measures to discourage the continued use of these highly polluting old vehicles, such as increasing the licence fees for old diesel commercial vehicles.  Our proposal, however, was not supported by the Panel.  We also proposed at the meeting of the Subcommittee on Improving Air Quality of the Panel on Environmental Affairs on March 10, 2010 to revisit the proposal, but Members still had reservations about the proposal.  We will continue to follow up on the above proposal and other disincentive measures with the Panel, so as to expedite the retirement of highly polluting commercial vehicles and improve roadside air quality.

(e) The Government follows international practices by requiring vehicle suppliers to provide sufficient information to prove that vehicles supplied to Hong Kong meet local statutory requirements in respect of safety, emissions and noise before their first registration.  Euro IV and Euro V diesel light bus models are registered in Hong Kong according to the above established procedures.  Following the type-approval of vehicle models, the EPD requires the vehicle manufacturer to randomly select the relevant vehicle model from the production line for emission tests and submit a test report annually.  The EPD also sends professional staff to check the quality control measures at the vehicle manufacturing plant.  Should there be  problems involving individual models, we will follow-up with the trade and the vehicle supplier concerned to solve the problems.

(f) As explained in the first two paragraphs of this reply, to meet Euro IV or more stringent particulates emission standards, light bus manufacturers have adopted DPFs.  During the operation of the vehicle, a DPF traps the particulates and burns them away for regeneration.  Manual regeneration will be activated only when the DPF fails to remove the trapped particulates, resulting in an excessive accumulation of particulates.  Therefore, under normal operation, the overall exhaust emission performance of the PLB can meet their designed emission standards, irrespective of whether the regeneration is in automatic or manual mode.

Ends/Wednesday, November 17, 2010
Issued at HKT 12:28


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