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Author: Tang Ming Chung, Kelvin, LLB IV; HKU

Date: 11/8/10


It is estimated that replacing all diesel light buses with LPG ones could reduce about 4% respirable suspended particulates (RSP) and 2% of nitrogen oxides (NOx) emitted from motor vehicles. (1) An LPG PLB emits almost zero RSP and only 50% of NOx of a Euro III diesel PLB. Electric PLBs are emission-free. (2) Both LPG and electric PLBs would be suitable for use in Hong Kong. However, the latter would be suitable for shorter routes only because of battery constraints. (2)


LPG light buses could meet the technical requirements of the light bus trade for local operations, with fuel costs, repair and maintenance requirements similar to the current diesel light buses. (1) However, the distance of operating routes and LPG filling stations would affect the operating cost and revenue of operators, and LPG buses would require larger LPG tanks and improved fuel efficiency to reduce the frequency of refueling. (1)


On the other hand, Electric light buses emit no exhaust at street level. (1) However, not all light bus routes are suitable for operation of electric light buses due to the need of re-charging facilities and relatively low range per charges. (1)


Although the cost of recharging is lower than fuel cost, total fuel cost is higher than diesel light buses if the cost of the battery is included. Batteries also require frequent maintenance. (1) Electric light buses have less repair and maintenance requirements for engine related components than diesel light buses, but more repair and maintenance for their electronic components. (1)


95% of 116 passenger questionnaires distributed in the trial period supported large-scale introduction of alternative-fuelled light buses to improve air quality. (1)


Despite the lower LPG price compared with diesel, operators of PLB routes that are some distance from LPG stations will experience net income reduction if they replace their vehicles with LPG ones. This is because they would have to go out of the way to refill their fuel tanks. Some might also have to refill more frequently as LPG is less efficient than diesel (one litre of diesel allows a PLB to run 87% higher mileage than one litre of LPG). During the refilling periods, they would have to stop operating and receive no fare at all. (2) According to a route-by-route analysis conducted by the Transport Department, 68% of the PLB operators will experience a net income increase from a marginal amount to $3,000 a month if they replace their diesel PLBs with LPG ones. The remaining 32% will face net income reduction from a marginal amount to above $3,000 a month because of loss in business time owing to longer or more frequent travelling for refueling. (3)


Since there is no feasible solution to the income reduction that will be experienced by some PLB operators, the Transport Bureau and Transport Department considered that a mandatory replacement scheme should not be pursued. (2) Relying on the natural replacement of existing PLBs with diesel ones that meet the latest emission standard of Euro III will mean that by the end of 2005, only 75% of the RSP and 40% of the NOx reductions anticipated under a full and mandatory replacement scheme would be achieved. (2) The Transport Bureau and Transport Department thus proposed to offer incentives in the form of an one-off grant with deadline for applications to encourage early replacements. (2) With the government subsidizing mini bus owners to replace diesel light buses with LPG or electric buses since 2002. More than 75% of vehicles have switched to using LPG. (4)


If 68% of the PLBs and half of the existing 16-seat private diesel light buses are replaced by LPG models and assuming that very few will opt for an electric model, 90% of the RSP and 70% of the NOx reductions anticipated under a full and mandatory replacement scheme will be achieved. (3)

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