Environment Hong Kong 2009
 
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Chapter 7 Noise

Mission

To prevent, minimise and resolve environmental noise problems through the formulation of noise policy, intervention in the planning process, the implementation of noise abatement measures and enforcement of the Noise Control Ordinance.

THE DIMENSIONS OF TRAFFIC NOISE

Highlights in 2008

  • Low-noise road surfaces had been applied to 37 local road sections by the end of 2008, benefiting 70 000 people.
  • Work was underway to retrofit noise barriers on 10 road sections.
  • The coverage of Designated Areas under the Noise Control Ordinance was expanded to protect more residents from construction noise.

TRAFFIC noise is the most enduring and problematic noise problem in Hong Kong. About 1.1 million people – one in seven residents – are exposed to excessive traffic noise. The Environmental Protection Department (EPD) has been working hard to address this problem, but the solutions are often not easy.

Hong Kong has dense high-rise developments, with residential blocks up to 60 storeys high sandwiched between busy roads, flyovers and junctions. The steep terrain in parts of Hong Kong and the use of elevated roads and other structures that can bring noise closer to recipients also present stumbling blocks to solutions.

The EPD is applying engineering solutions to the problem, such as noise barriers and low noise surface roads, but these require public understanding and support, especially barriers. We have developed sophisticated tools to address people's concerns and ensure they comprehend the present and future traffic noise scenarios, with and without solutions. We are also continuing to test out new technologies and materials to reduce noise. Our ultimate goal is to achieve more tolerable traffic noise levels for everyone in Hong Kong.

Photo - Residential blocks sandwiched between busy roads.

Traffic noise in 3-D

One of our greatest challenges has been how to illustrate traffic noise. Non-experts have much difficulty grasping the impact of noise levels as represented in numerical tables and two-dimensional maps. Yet public understanding is very important when it comes to the acceptance of noise barriers and other solutions.

To improve understanding, the EPD has developed a tool that produces 3-D noise models. This is especially relevant in Hong Kong, where most people live in high-rises and the noise impacts differ depending on the floor they live on. Our 3-D noise model can show the impact on each floor and even in particular flats because it is focused on noise receivers (the people living in the flats) rather than noise sources (the vehicles on the road).

The model comprises three parts. First is a basic 3-D geographical model with information on the terrain, ground surface type, and traffic flow, composition and speed. Added to this is a computational model that calculates noise levels at one metre from the building façade. This is generated for 3-metre-by-3-metre blocks, thereby measuring impacts along the height and width of a building. Finally, a photorealistic model is used to turn all of this information into an easily-understood image.

Noise levels are represented in colour and usually the purple and red hues show the noisiest places. Viewers can decide on a vantage point and walk, drive and fly through the site. Most importantly, they can see what noise levels are like with and without mitigation measures such as noise barriers. This is a crucial step in ensuring that public concerns are addressed before any final decisions are taken.

The tool has been used with much success. It was debuted in a presentation to the Kwun Tung District Council in 2005 for a barrier retrofit project on Tseung Kwan O Road. The District Councillors were able to quickly grasp the essential details of the project, which greatly facilitated discussion and resulted in constructive feedback. The project was subsequently approved.

Photo - 3-D models of Tseung Kwan O Road Project show noise levels at building façades without noise barriers (left) and with them (right).

The 3-D tool was also used to illustrate proposed noise barriers on Hung Mui Kuk Road and Che Kung Miu Road in a meeting with the Sha Tin District Council. The District Councillors were impressed by the quality of information that the 3-D tool provided although they subsequently decided not to approve the barriers.

The EPD has taken the 3-D concept further by incorporating virtual reality technology. Users not only can see the images in greater depth using polarised glasses, but also hear the actual noise levels. This is like bringing them to the site without having to leave their desks and it shows in a highly realistic way how noise barriers can make a difference.

We have extended the 3-D tool to a wider audience by uploading projects onto our website. Using video streaming, people can view and consider the information on proposed barrier retrofit projects anytime, anywhere, at their convenience.

By making it easier for the public to understand our proposals and providing opportunities for feedback, we can ensure their views are taken fully into account as we continue to seek solutions to traffic noise.

Photo - A 3-D model is displayed in a public consultation.

A low-noise 'carpet' on city streets

3-D tools aid understanding about noise barriers, but we have another engineering solution to counter traffic noise – low-noise road surfaces (LNRSs).

LNRSs have been applied to new high speed roads for years, reducing noise by 5 dB(A). Initially, it was not possible to apply them to existing city streets because they would deteriorate too quickly under the stop-start driving and other traffic conditions. But the composition was improved and binders were added to the material, enhancing its durability and making it suitable for a trial on city streets.

Photo -High-speed roads covered with low-noise road surfaces.

Almost 100 road sections have been identified for trial with LNRSs, representing different types of roads, terrains and traffic conditions. By the end of 2008, 37 road sections had been resurfaced, benefiting 70 000 people. The EPD conducted a mid-term review of the programme and found LNRSs had a positive effect – they reduced noise by 2 dB(A) and changed the frequency of the noise, making it less annoying to nearby residents. The durability of the material was generally acceptable, apart from areas near bus stops and shops, where dust and dirt caused the road surface to deteriorate.

The EPD will continue to test the remaining road sections and expects to have preliminary findings within two years, when we will discuss the results with the Highways Department. Our hope is that LNRSs will be found to be suitable as a standard paving material for Hong Kong's roads.

Hong Kong's traffic noise will not go away, but by adapting new technologies and continuing to enhance public understanding of the problem, it should be possible to reduce noise in the constrained environment of our city streets.

Looking Ahead

  • Work will continue on retrofitting noise barriers at noisy road sections and laying low-noise surfaces on roads selected for a trial programme.
  • The 3-D noise models and maps will be used more extensively in projects to facilitate public engagement.
 
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