Environment Bureau Environmental Protection Department ENVIRONMENT HONG KONG 2008
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7 Noise

 
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Mission

 

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


THE GEOGRAPHY OF NOISE


Highlights in 2007
  • By the end of 2007, 34 local road sections had been re-surfaced with low noise road surfaces, benefiting some 62 000 people.
  • 26 new local road sections were identified for extended trials of low noise road surfacing materials.
  • A study to explore the use of rubberised asphalt as a low noise road surface material was in progress.
  • Work was underway to retrofit noise barriers on three road sections.
  • Guidance notes on good driving and maintenance practices were distributed to the trades and the public.
  • 116 planning schemes and strategic proposals were reviewed, benefiting more than 24 000 people.

More than one million people are exposed to excessive traffic noise in Hong Kong. The Environmental Protection Department (EPD) has worked diligently for many years to reduce the problem through planning, control and mitigation. In 2007, for instance, we achieved good progress in making road surfaces quieter, building barriers to noise and enhancing driver awareness. But we are also conscious of the need to make the public better informed about issues so they can understand and support the solutions. In the past two years we have introduced a territory-wide noise map and three-dimensional (3-D) noise model that identifies the noisiest streets in the city – not only at ground level, but vertically, up to the top of high rises. This new tool is useful both in public consultations and in helping us to refine our noise strategies.

Residential buildings facing a busy highway.

Residential buildings facing a busy highway.

Mapping noise

Noise maps depict the extent of excessive traffic noise and the buildings affected. They are increasingly being recognised internationally as an important tool in noise management. Hong Kong has been a leader in this respect because we were among the first places to develop a city noise map and 3-D noise models for projects. A 3-D noise model is necessary because of the concentration of high rises in Hong Kong. Unlike a two-dimensional model, the 3-D one can show the noise impacts on every floor of a building, rather than just at ground level (see How We Map Noise in Hong Kong for details).

 

3-D models of Sha Tin Road show noise levels at different heights without noise barrier protection (left), and with noise barrier protection (right).

3-D models of Sha Tin Road show noise levels at different heights without noise barrier protection (left), and with noise barrier protection (right).

The Hong Kong noise map, published on the EPD web site in 2006, shows that 1.14 million people are exposed to traffic noise exceeding 70dB(A). The worst affected district is Yau Tsim Mong, where almost 40 per cent of homes are exposed. Older urban areas like this one generally experience the worst traffic noise problems because they were developed when noise control was not really a priority. They are also the most difficult areas to achieve improvements because of the density of development.

With the noise map and 3-D noise model, we are able to pinpoint the buildings and even the flats most affected by traffic noise. This has three benefits. It gives us a better idea of where to target noise reduction measures, it helps the public to understand the noise situation in Hong Kong, and in future it will help us to gauge the effectiveness of our efforts when we update the map.

This map shows the spatial distribution of traffic noise in Hong Kong.

This map shows the spatial distribution of traffic noise in Hong Kong.


Low noise road surfaces

Asphalt rubber is used as a highway surface material in Arizona, USA.

Asphalt rubber is used as a highway surface material in Arizona, USA.
Roads in older urban areas, like those in Yau Tsim Mong, are a major concern. They contain a dense, jumbled mix of residential and commercial buildings, utilities, signs and other facilities and they generally cannot accommodate noise barriers due to site constraints, such as insufficient space and sightline problems. The EPD therefore is exploring other engineering solutions, such as low noise road surfaces on local roads.

Low noise road surfaces can reduce the road-tyre noise. A number of local roads have been identified for a trial of these surfaces. The selected roads have to be fairly flat and should not be subject to frequent stop-go traffic and heavy vehicle usage, which wear down the low noise road surfaces. By the end of the year re-surfacing had been completed on 34 road sections, benefiting some 62 000 people.

The EPD is also interested in improving the durability and acoustic performance of low noise road surfaces, which currently reduce noise by one to three decibels on local roads. Overseas experience has shown smaller aggregate and thicker surfaces may perform even better so we are working with the Highways Department to test other design mixes in Hong Kong driving conditions. One study in progress uses rubberised asphalt for road resurfacing. The asphalt is mixed with chips from shredded waste tyres so it potentially has a double benefit of re-using recyclable material, as well as reducing noise (see Testing Road Surfaces for details).


Noise barriers

Noise barriers are another key strategy to reduce road traffic noise impact. The EPD has identified some 30 existing road sections for barriers, of which two are already installed. Barriers can be highly effective in blocking out noise. However, their application is subject to many engineering and related constraints.

Structures at street level and utilities below ground can prevent barriers from being built. Fire-fighting access and traffic safety cannot be compromised. Greening provisions and the visual impact of barriers are also concerns. A better barrier design may overcome some of these issues. In 2007 the EPD commissioned a study to look at new trends in barrier design in terms of attractiveness, acoustic effectiveness and environmental provisions.

 

3-D models of Tseung Kwan O Road (left) and Tsing Tsuen Bridge (right) which will be retrofitted with noise barriers.

3-D models of Tseung Kwan O Road (left) and Tsing Tsuen Bridge (right) which will be retrofitted with noise barriers.


Educating drivers and the public

Engineering solutions, such as barriers and quiet road surfaces, can minimise the effects of traffic noise, but drivers also have a role to play. They can reduce noise nuisance by maintaining their vehicles properly and practicing good driving habits, such as driving in the proper gear, avoiding unnecessary use of horns, not revving the engine while idling and not braking too hard.

To engage stakeholders in this issue, the EPD and Transport Department (TD) jointly prepared two leaflets on good driving habits and vehicle maintenance practices in consultation with the franchised bus operators, vehicle repair trade, Hong Kong Institute of Vocational Education, Hong Kong Automobile Association and other interested parties. These leaflets were launched in July 2007 and more than 20 000 were distributed. Relevant information was also uploaded to the web sites of the EPD and TD for use by the public.

An educated public can make a difference when it comes to controlling noise. If they understand the constraints and effectiveness of noise control measures, they are more likely to support them. The noise map and 3-D noise-modelling tool are helping in this regard. During public consultations on barrier projects, we combine sound with our 3-D noise model so people can hear, as well as see, the effects of noise barriers. This has paved the way for greater acceptance of this solution. Seven consultations using this tool were held in 2007.

Public engagement is an on-going process. The EPD can suggest solutions to road noise, but we recognise the need to go a step further to convince people of the benefits. The use of barriers, low noise road surfaces and other measures to reduce traffic noise is a change for the good and improves the quality of life for all residents.

Leaflets on good driving habits and good vehicle maintenance provide the public with information on how they can reduce traffic noise.

Leaflets on good driving habits and good vehicle maintenance provide the public with information on how they can reduce traffic noise.


Looking Ahead
Looking Ahead
 
  • Work will continue to progressively retrofit noise barriers and carry out a trial of low noise road surfaces on selected road sections.
  • Some 120 planning schemes and strategic proposals will be reviewed to minimise noise problems for about 27 000 people.

Topical Issues