Carbon savings from HK’s flagship road “short term”, says transport expert

"We can't build our way out of congestion"

New bypass West Ventilation Building

Highways Department project manager Kelvin Lo claims a new bypass will clean the air and reduce CO2


A leading transport expert has cast doubts on the Hong Kong government’s claims that the new HK$36 billion Central-Wan Chai Bypass will reduce carbon dioxide emissions.

Speaking to Blue Skies China, David Metz, Honorary Professor, Centre for Transport Studies at University College London and formerly Chief Scientist for the UK’s Department for Transport, said that a faster journey time could reduce carbon emissions only if trip origins and destinations were fixed. “But what we observe is that average travel time is invariant, which means that people take advantage of investment that allows faster travel to travel further, to have more choice of opportunities and destination. This means more traffic and more carbon emissions in the long run. So time savings and congestion relief are short term,” he said.

Metz’s comments come in reaction to the government’s claims the new road will cut carbon emissions by shortening the journey from Central to the Island Eastern Corridor from 30 minutes to five minutes. “Every year, we estimate that it can reduce the carbon dioxide by 11,000 tonnes,” said Mr. Kelvin Lo, Highways Department Project Manager/Major Works. “This is equivalent to the absorption power of 480,000 trees, which is equivalent to 67 Victoria Parks,” he said (not mentioning that Victoria Park was reduced in size by about 0.5 acres with 290 trees removed to make way for a slip road for the bypass in 2013).

But Metz said building new road capacity was not the route to lower congestion. “We know from experience that we can’t build our way out of congestion. Adding road capacity increases the volume of traffic and hence carbon emissions, although electric vehicles (and non-fossil fuel electric generation) will eventually deal with carbon from surface transport,” he said.

Closer investigation shows gaps in air purification claims

The new 4.5km link road is unique in that it will use the world’s largest air purification system to clean pollution from the tunnel portion of the road – around 3.7km. “Every hour it can handle 5.4 million cubic metres of vehicle exhaust and reduce 80% of the RSPs and nitrogen dioxide from the tunnel exhaust,” said Lo.

In the system, the exhaust will pass through two major components that remove the pollutants. It will first go through the electrostatic precipitator that separates respirable suspended particulates, which are charged and attracted to collector plates. Nitrogen dioxide will then be removed from the exhaust in the system’s denitrification filter which is filled with activated carbon. Purified air, the government says, will then exit the system.

However, while green groups have welcomed the air purification technology and called for it to be duplicated across other projects, it is less widely reported that the air purification technology only applies to the East Tunnel Portal. According to the project’s Environmental Impact Assessment (EIA), electrostatic precipitators will remove about 80% of the dust pollutants and about 70% of the odour at the East Tunnel Portal while there are no such purification facilities at the two other exhaust portals, the West Ventilation Building and Central Ventilation Building. Also less widely reported is that the project passed its EIA in 2007 based on Hong Kong’s historic Air Quality Objectives (pre-2013), which allowed significantly higher pollution than today. Allowable annual average RSPs at the time were 180µg/m³ compared with an annual average of 50µg/m³ today, for example.

The government had not responded to questions on this, the energy requirements of its air purification technology, nor the assumptions behind its emissions calculations, at press time.

About James Ockenden (300 Articles)
Writer, journalist and sustainability consultant with a passion for clean technology and public health. 25 years covering power and energy markets: former editor of Power Plant Technology, International Power Generation, Asian Electricity, Aircraft Economics, Energy Risk, Asia Risk, Benchmark; writer for South China Morning Post, Cathay Dragon's Silkroad, APlus, Veolia's "Planet", Hong Kong Tatler; founder of Blue Skies China. MSocSc in Corporate Environmental Governance, University of Hong Kong; BA & MA degree in Natural Sciences (major in Materials Science & Metallurgy), Cambridge University.
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