Nam Kee’s hybrid minibus, partly funded by the government, performed badly in terms of running costs, downtime and tailpipe emissions

A hybrid green minibus plying routes between Kwun Tong and Lok Wah Estate had running costs more than twice those of its 15-year-old LPG counterpart, according to the final report of the machine’s two-year trial under a government subsidy scheme.

The hybrid bus, a 2017 GMI Gemini diesel-electric, cost its operator Nam Kee an average of HK$5.55 per kilometre over the subsidy trial period, against HK$2.43 per kilometre for a bus earmarked for comparison, a 2005 Toyota running on LPG.

Nam Kee’s new hybrid beat its old LPG bus in term of carbon emissions but in every other category the old bus reigned

Fuel costs accounted for most of the extra outlay, as the hybrid ran on more expensive – and dirtier – diesel fuel. And while greenhouse gas emissions were calculated as slightly lower for the hybrid, its tailpipe emissions were considerably higher than the older LPG bus: the hybrid emitted around 0.3 tonnes of nitrogen oxides (NOx) and 0.3 tonnes of particulates over two years, against just 30 kg of NOx and virtually zero particulates for the LPG bus.

This 15-year-old LPG bus has proven reliable and relatively clean

According to the Centre for Health Protection, long-term exposure to nitrogen dioxide can lower a person’s lung function and resistance to respiratory infections, while particulates are proven carcinogenic to humans and have been linked to premature deaths in the city.

Adding to the hybrid woes was extensive downtime: a total of 29 days scheduled and unscheduled maintenance against two days off for the old bus, over the two years.

The 19-seater bus was partly funded by the Environmental Protection Department under the government’s HK$300 million Pilot Green Transport Fund, a scheme that  aims to promote and test new vehicle technologies. The scheme came under fire recently for lengthy delays in the publishing of test reports into the subsidy vehicles’ performance. Reports for over 40 vehicles, some funded as far back as 2014, have still not been made public.