Advisory Council on the Environment | Environmental Protection Department

Measures to Address Noise Impact of Existing Roads

(ACE Paper 39/2000)
For discussion

PURPOSE

This paper briefs Members on the new policy to address noise impact of existing roads on residents in the neighbourhood.

INTRODUCTION

The Executive Council has approved the Government's proposal of introducing a new policy to address the noise impact of existing roads on residents. Under the new policy, -
1. engineering solutions, by way of retrofitting of barriers and enclosures, and resurfacing with low noise material, should be implemented where practicable at existing excessively noisy roads in accordance with the guidelines set out in paragraphs 8 and 14 below; and
2. non engineering solutions, such as traffic management measures, should be explored on a case-by-case basis and implemented where practicable at roads where engineering solutions are impracticable or where engineering solutions alone are inadequate in reducing the noise to an acceptable level.

BACKGROUND

Noise Limit

We have adopted the existing noise limit of 70dB(A) L(10) (1 hour)¹ ("the noise limit") in the Planning Standards and Guidelines since mid-1980's for the planning of new roads. As Annex A shows, this limit is the same as in the UK and USA, and less stringent when compared with Australia and the Netherlands.

Existing policy for mitigating traffic noise

Under existing policy, when planning new roads, the relevant department or developer must ensure that traffic noise will stay below the noise limit. If it is envisaged that traffic noise generated will exceed the noise limit, they must adopt all practicable direct measures such as adjusting the alignment and erecting barriers or enclosures to reduce the impact on residents in the neighbourhood. Where direct measures are inadequate, they have to provide affected residents with indirect technical remedies in the form of good quality window and air-conditioning. The current policy applies to new roads only.
To ensure that individual vehicles do not produce excessive noise, we introduced legislation in 1995 requiring all newly registered vehicles to comply with stringent noise standards. We will continue to move in step with the European Union on this front. In addition, we have resurfaced all high-speed (70km/hr or above) roads with low noise material except those with steep gradient or sharp bends where the use of such material is unsuitable. The material has reduced noise by about 4 dB(A). However, the effect of the resurfacing programme in reducing noise is limited: it covers only 11 km of all roads.

The problem with existing roads

According to Environmental Protection Department's assessment, 655 out of the 3,000 existing roads in Hong Kong are currently generating noise in excess of the noise limit. The majority of these roads were planned and constructed before the existing policy for new roads took effect. The increase in traffic has exposed more families to high levels of traffic noise above 70dB(A). This does not mean, however, all flats near these 655 roads are exposed to high noise levels. This is because the degree of noise impact would depend on factors including height and location of the flats and any structure that screens the line-of-sight to the road. For example, flats screened by podium, building structure or are facing away from the road would be less affected by traffic noise.

THE NEW POLICY

Retrofitting of barriers/enclosures

With the erection of barriers or enclosures, neighbouring residents would experience noise reduction from 1 to 19 dB depending on the height and location of their units relative to the barriers/enclosures. Environmental Protection Department has studied the feasibility of retrofitting barriers/enclosures on existing roads that are generating noise in excess of the noise limit and concluded that it would be technically feasible to retrofit such structures on a limited number of roads.

Guiding Principles

Based on Environmental Protection Department's studies, barriers/enclosures will be retrofitted on roads -
1. where they are generating noise in excess of the noise limit for residential premises along their alignment; and
2. where the retrofitting of such structures is technically feasible, that is -
  - the new structures will not obstruct emergency access or fire fighting;
  - they will not undermine road safety or impede pedestrian and vehicular movements;
  - they will not interfere with commercial activities or cause social disruptions; and
  - there will be adequate space for the retrofitting.

Need for aesthetic design

In pursuing the retrofitting programme, it is important that we pay due attention to the design of the barriers or enclosures. Otherwise, we will be resolving one problem and creating eyesores on the landscape. To prevent the barriers/enclosures from being unduly obtrusive, the landscape and visual impacts would be included in the environmental impact assessment process of the retrofitting programme. Possible design that would enhance the landscape and visual quality or make the project visually compatible with the vicinity would be fully explored. Some examples of such designs are at Annex B . In addition, the environmental impact assessment would include air quality impact and disturbance of existing vegetation to ensure that such environmental considerations are not unduly compromised.

Phasing the retrofitting works

Based on the guiding principles in paragraph 8 above, we have currently identified 29 existing road sections (including 6 flyovers) for retrofitting. We estimate that 24,000 residential units will benefit from the programme. For the majority of the beneficiaries (70%), the programme will reduce the noise to which they are exposed to a level below the noise limit.
The retrofitting programme is massive. Subject to availability of funds, we intend to implement it in stages with priority given to roads with the highest noise exposure and number of affected residents. A preliminary implementation timetable has been drawn up at Annex C. We will consider refining it to also synchronise the timing for retrofitting certain roads with that of new roads that have already been planned to adjoin them. This will minimize disturbance to residents and road users arising from the different works projects and where possible achieve some savings in the project costs.
It should be noted that the proposed retrofitting programme covers only 4% of the 655 excessively noisy roads currently identified. There are still over 600 excessively noisy roads that we need to deal with.

Resurfacing with low noise material

As mentioned in paragraph 5 above, the low noise resurfacing programme has been restricted to existing high-speed roads. The material is considered less suitable for local roads where frequent stop and start due to traffic lights, loading and unloading activities and parking would shorten its life considerably. It is estimated that while a local road with normal asphalt surface needs resurfacing once every six years, one with this type of low noise surfacing needs to be resurfaced at least once every three years. This would mean higher maintenance costs, more traffic disruption and inconvenience to drivers, pedestrians and shop operators. Consequently, under existing policy, low noise surfacing materials are used on new local roads under exceptional circumstances where noise reduction is an absolute necessity but cannot be achieved by any other means.
We will extend the above policy for new local roads to existing local roads. Environmental Protection Department has currently identified 72 roads as candidates for feasibility study. The preliminary assessment is that 36 of these roads will meet the site geometry and traffic volume for the low noise surfacing materials to be effectively applied while the remaining 36 will exceed the desired traffic volume control by up to 20%. This will mean that if low noise surfacing is applied to these 72 road sections, half of them may need to be resurfaced once every two years instead of three years. The feasibility of resurfacing these 72 road sections will be studied by Environmental Protection Department and Highways Department in details taking into account other engineering considerations. Subject to satisfactory results of the study, a resurfacing programme will be implemented.
We estimate that the resurfacing of the 72 road sections will benefit 40,000 residential units. About 11% of them will experience a reduction in noise to a level below the noise limit after the resurfacing.

Non-engineering measures

For the existing excessively noisy roads where engineering solutions are impracticable, and for roads where engineering solutions would not be adequate in reducing the noise level to below the noise limit, we will explore on a selective basis and implement non-engineering options such as traffic management measures where practicable case-by-case.
However, any control measures would benefit some and inconvenience others. Considerable operational and enforcement problems are involved. We need to examine the feasibility of introducing such solutions most carefully and will consult the relevant District Councils and the transport trade in considering such proposals. In the longer term, the noise impact of the existing roads should be addressed in a comprehensive manner through urban renewal and better town planning efforts.

WAY FORWARD

There is no ideal solution to address the noise impact of existing roads on residents, which has existed for many years. But the Administration is doing all it can within the current constraints. Although we expect that the exposure of some residents to excessive traffic noise after implementation of the above proposals would still be unavoidable, the proposed measures would have an appreciable mitigating effect and bring overall improvement to the living environment of those being affected by excessive traffic noise generated from existing roads.
We will brief the relevant District Councils (DCs) on the new policy and the proposed implementation programme. We will seek funding for the retrofitting and road resurfacing works for the roads currently identified, and for any additional roads covered by the new policy.

Environment and Food Bureau
December 2000

¹ L10(1 hour) is the noise level exceeded for 10% of an one-hour period, generally used for road noise at peak traffic flow.