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Road Traffic Noise Guidelines

Transport Services Division

ENVIRONMENTStandards & Guidelines

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DPTI Road Traffic Noise Guidelines

Department of Planning Transport and InfrastructureRoad Traffic Noise GuidelinesFirst published: 1990First Update: February 2002Second Update: March 2007Third Update: December 2014Fourth Update: October 2016Version: 5

Copyright Department of Planning Transport and Infrastructure77 Grenfell Street Adelaide, SA 5000

The guidelines were developed by the Environmental Group, Projects Directorate, Safety and Services Division with the assistance of Resonate Acoustics and Roads and Maritime Services.

It has been approved and authorised for use by Departmental staff and its authorised agents by:

General Manager, Asset Management

and endorsed by the Environment Protection Authority..

Extracts may be reproduced providing the subject is kept in context and the source is acknowledged. Every effort has been made to supply complete and accurate information. This document is subject to continual revision and may change.

To ensure you have the most up-to-date version of this document refer to: http://www.dpti.sa.gov.au/standards/environment

For information regarding the interpretation of this document contact:Asset Management – Technical ServicesTelephone: (08) 8343 2686 Facsimile: (08) 8343 2905

K-Net Doc: 1791402 UNCONTROLLED COPY WHEN PRINTEDVersion No.: 5Issue Date: October 2016Doc. Owner: Senior Environmental Management Officer of 39

http://www.dpti.sa.gov.au/standards/environment


TABLE OF CONTENTS

GLOSSARY.....................................................................................................................5

1 INTRODUCTION.......................................................................................................6

2 THE NATURE OF ROAD TRAFFIC NOISE.............................................................8

2.1 WHAT IS NOISE? 8

2.2 PRESSURE OR LOUDNESS 8

2.3 HUMAN PERCEPTION TO A NOISE LEVEL CHANGE 9

2.4 THE A-WEIGHTED DECIBEL SCALE 9

2.5 TYPES OF ROAD NOISE 11

2.6 FACTORS INFLUENCING ROAD TRAFFIC NOISE GENERATION 11

2.7 NOISE DESCRIPTORS 13

2.8 NOISE MITIGATION MEASURES 132.8.1 Noise control at the source........................................................................................................142.8.2 Noise control along the transmission path.................................................................................142.8.3 Noise control at the receiver......................................................................................................14

3 ASSESSMENT PROCESS.....................................................................................16

3.1 SCOPE OR APPLICATION OF THE GUIDELINES 163.1.1 Scope Definition......................................................................................................................... 163.1.2 Noise Sensitive Receivers.........................................................................................................163.1.3 Noise Catchment Areas and Grouping Receivers.....................................................................173.1.4 Responsibility for Mitigating Traffic Noise..................................................................................17

3.2 NOISE ASSESSMENT CRITERIA 183.2.1 Noise Descriptors....................................................................................................................... 183.2.2 Noise Criteria............................................................................................................................. 183.2.3 Relative Increase Criterion.........................................................................................................193.2.4 Transitioning Between Noise Catchment Areas with Different Criteria......................................193.2.5 Noise Assessment Location.......................................................................................................193.2.6 When should Noise Mitigation be considered?..........................................................................203.2.7 Flowchart of Assessment Process.............................................................................................20

4 NOISE MITIGATION DESIGN................................................................................23

4.1 ROAD DESIGN 23

4.2 NOISE BARRIERS 234.2.1 Barrier Design............................................................................................................................ 244.2.2 Noise Barrier Benefit..................................................................................................................244.2.3 Barrier Materials........................................................................................................................25

4.3 PROPERTY TREATMENT 254.3.1 Facade Treatment Criteria.........................................................................................................26



4.3.2 Facade Treatment Packages.....................................................................................................274.3.3 Facade Treatments to Noise Sensitive Non-Habitable Spaces.................................................304.3.4 Mechanical Ventilation...............................................................................................................304.3.5 Acoustic Screening.................................................................................................................... 30

4.4 NOISE MITIGATION GENERAL NOTES 30

5 PROCESS FOR ASSESSING ROAD TRAFFIC NOISE........................................31

5.1 GENERAL 31

5.2 PUBLIC ANNOUNCEMENT OF A ROAD PROJECT 32

5.3 NOISE ASSESSMENT BOUNDARY 32

5.4 MODELLING ROAD TRAFFIC NOISE 335.4.1 Noise Model Validation..............................................................................................................335.4.2 Noise Model inputs....................................................................................................................335.4.3 Road surface corrections...........................................................................................................345.4.4 Meteorological Effects................................................................................................................34

5.5 DEVELOPMENT OF A NOISE MITIGATION PLAN 345.5.1 Reasonable and Practicable Mitigation......................................................................................345.5.2 Community Acceptance.............................................................................................................355.5.3 Noise Mitigation Plan................................................................................................................. 36

5.6 DATABASE OF NOISE MITIGATION TREATMENTS 36

5.7 POST CONSTRUCTION VERIFICATION 36

6. BIBLIOGRAPHY.....................................................................................................37

APPENDIX A.................................................................................................................38



GLOSSARY

dB Decibel. A unit of measurement used to express sound level. It is based on a logarithmic scale, which means a sound that is 3 dB higher has twice as much energy.

dB(A) Units of the A-weighted sound level. A-weighting is defined in the International standard IEC 61672:2003 and relates to the measurement of sound pressure level. A-weighting is applied to instrument-measured sound levels in effort to account for the relative loudness perceived by the human ear at typical sound pressure levels, as the ear is less sensitive to low audio frequencies.

EPA South Australian Environment Protection Authority.

EquivalentNoise Level - Leq

The Leq is the value of a steady noise that would have the same acoustic energy as the varying noise, over the same time period. All references in these Guidelines are to A-weighted noise levels i.e. LAeq

LAeq (15hr)

(LAeq day)The noise descriptor refers to the A-weighted energy averaged equivalent noise level over a 15 hour day time period between 7 a m and 10 p m.

LAeq (9hr) (LAeq night)

The noise descriptor refers to the A-weighted energy averaged equivalent noise level over a 9 hour night time period between 10 p m and 7 a m.

L10 The noise descriptor L10 refers to the noise level which is exceeded for 10% of the time in a given measurement period, and corresponds to the average of the upper noise levels.

RW Weighted Sound Reduction Index—A laboratory measured value of the acoustic separation provided by a single building element (such as a partition). The higher the RW the better the noise isolation provided by a building element.

Rw + Ctr A measure of the sound insulation performance of a building element with a Ctr spectrum adaptation term placing greater emphasis on the low frequency performance.

Insertion Loss (IL)

Insertion loss of barriers is the difference in sound pressure levels at a specified receiver position before and after the installation of barrier, provided that the noise source, terrain profiles, interfering obstructions and reflecting surfaces, if any, have not changed.

Significant When used in context with a change in noise level, the term ‘significant’ relates to an increase in level of greater than 2 dB(A) (i.e. ≥ 2.1 dB(A))

Residual Exceedance

The remaining exceedance of a noise assessment criterion following the application of noise mitigation measures.



1 INTRODUCTION

Increasing volumes of traffic and rising community awareness of the environment has led to traffic noise becoming an increasingly important consideration in urban development. The conflicting requirements of providing a quiet environment for people to live in, whilst maintaining a high standard road network for the safe and efficient transportation of increasing numbers of goods and people, presents a challenge to planners and designers involved in land-use planning and road location and design.

As road traffic noise is related to the volume of traffic, high levels are generally associated with the arterial road system. In 2010/11 the South Australian transport task totalled 28.8 billion passenger-kilometres and 37.5 billion tonne-kilometres. Since 2000/01 the South Australian domestic passenger and freight tasks have grown by 5.1% and 17.4% respectively.

Exposure to high traffic noise levels can give rise to various problems, including annoyance from disruption to leisure activities such as listening to music or watching television; speech interference; sleep disruption; decreased work efficiency and proficiency; and fatigue. The control of road traffic noise is therefore seen as having social and economic benefits to the community.

There is, however, a wide range of sensitivity to noise within the community. Some people are likely to be disturbed at relatively low levels of traffic noise, while others may not be disturbed even at relatively high levels. Similarly a range of individual responses could be expected for any given change in noise level. Tolerance to noise is influenced by the degree of acclimatisation, the level and nature of the intruding noise and the level of the background or ambient noise. The annoyance a person feels can also be influenced by the extent to which traffic noise interferes with activities such as reading, sleeping or watching television.

The Department, along with a range of other Federal, State and local agencies has a role in addressing the issue. The Department has a General Environmental Duty under Section 25 of the Environment Protection Act 1993. The Road Traffic Noise Guidelines is the Departments response to satisfying the General Environmental Duty in relation to infrastructure works. The Department will take reasonable and practicable measures to reduce the impact of traffic noise.

Complementary measures being undertaken by the Department to reduce the impacts of road traffic noise include enforcement of in-service vehicle noise emissions, contributing to setting national standards for new vehicles, and measures to manage travel demand and promote alternative modes.

The Development Division of DPTI provides guidance to planning authorities, developers and builders on measures that can be adopted to mitigate the impacts of traffic noise. In 2013 the Minister’s Specification SA 78B and the Noise and Air Emissions Overlay policy was introduced to protect sensitive land uses (e.g. residential) from noise emissions generated by major transit corridors. Where the Overlay is applied by Councils through the Development Plan Amendment process this provides protection to new dwellings from traffic noise. Further information is available in Reducing Noise and Air Impacts from road, rail and mixed land use – A Guide for builders, designers and the community.

The Road Traffic Noise Guidelines provides guidance to Departmental staff, consultants and contractors in addressing road traffic noise as a key part of infrastructure project development.



These Guidelines set out the process to be followed and criteria to be applied when assessing the road traffic noise impacts of infrastructure projects involving new roads and/or major upgrading of existing roads. This assessment is to be undertaken during the planning and design phase of such projects and documented in a Noise Mitigation Plan and the Environmental Impact Assessment Report or Project Impact Report, then implemented during construction.

These Guidelines should also be used in conjunction with the Department’s Noise Mitigation Manual that provides details on acoustic issues and design principles in relation to the use of noise barriers and architectural acoustic treatments for noise sensitive properties.



2 THE NATURE OF ROAD TRAFFIC NOISE

2.1 WHAT IS NOISE?Noise can be defined as unwanted sound. Sound is the sensation produced in the ear as a result of fluctuations in air pressure, superimposed on the steady atmospheric pressure. The ear responds to these much smaller fluctuations with great sensitivity.

The frequency of a sound is the rate at which the fluctuations occur. Practically all sounds contain a mixture of frequencies. Screeching or whistling noises are composed mainly of high frequency sound while rumbles or booms are composed mainly of low frequency sound. As an illustration, middle C on a piano is 256 Hz (hertz, or cycles per second), while 1,000 Hz is about the frequency of the high C that sopranos strive for.

The auditory senses are normally limited to frequencies between 20 and 20,000 Hz in a young person. The ability to hear the higher frequencies decreases with age, such that it is not uncommon for a 50 year old person to be unable to hear sounds above 8,000 Hz.

2.2 PRESSURE OR LOUDNESSThe range of sound pressures (loudness) encountered in everyday life extends from those which the human ear can just detect (the ‘threshold of hearing’) to those many times as great (approaching, and sometimes exceeding, the ‘threshold of pain’). The international standard unit of acoustic pressure is the micropascal (µPa), but as the range between the faintest audible sound and the loudest the ear can stand is so enormous (20 µPa to 63 million µPa), it would be very awkward to express sound pressure fluctuations in these units. Instead, this range is ‘compressed’ by expressing the sound pressure on a logarithmic scale, which is also the way the human hearing mechanism responds to pressure variations.

Sound is therefore described in terms of the Sound Pressure Level (SPL), the unit of which is the decibel (dB). In decibel notation, the entire audible range of sound pressure, described above with such large numbers in micropascals, runs from 0 to 130 dB. Zero decibels is an arbitrary noise energy intensity approximately equal to the lower limit of hearing of a young adult.

It must be remembered that the decibel scale is logarithmic. On a linear scale, the total sound pressure from two identical noise sources would be twice that from one of the sources alone. However, on the logarithmic decibel scale, the total sound pressure level from two identical noise sources is 3 dB higher than the level from either source alone. In other words, in the case of road traffic noise, a doubling of traffic flow leads to a 3 dB increase in the sound pressure level. Similarly, a halving of traffic flow results in a 3 dB decrease.

Although the ear can distinguish change of about 1 dB in a pure tone, the minimum that can be detected for a varying source such as traffic noise is about 3 dB. In addition, each increase of approximately 10 dB sounds subjectively twice as loud to the ear (Refer Section 2.3). Therefore a noise measured at 80 dB will sound twice as loud as one which registers 70 dB, which in turn will appear twice as loud as one which registers 60 dB.

Although a risk of temporary or permanent damage exists for people exposed for prolonged periods to noise levels above about 90 dB, higher levels can be tolerated without damage for shorter exposure times.



2.3 HUMAN PERCEPTION TO A NOISE LEVEL CHANGEHow we subjectively perceive a change to traffic noise exposure under typical living conditions versus a noise level change is outlined in the table below:

Perceived volume change Noise level change (dB)

Doubling or halving 6 – 10

Noticeable change 3 – 5

Not noticeable change 0 – 2

2.4 THE A-WEIGHTED DECIBEL SCALEAlthough the perceived loudness of a sound depends primarily on sound pressure, it is also influenced by frequency. The human ear is most sensitive to mid-range and high frequencies (approximately 1,000 – 8,000 Hz) and is less sensitive to the lower frequencies.

To ensure measured levels approximate the human response, a weighting scale is used. It is known as the ‘A’ scale and the units are referred to as ‘A’ weighted decibels (written as dB(A)). The dB(A) scale discriminates between sounds in much the same way as people do.

It should be noted that noise levels (whether predicted or measured) are usually expressed as whole numbers. Decimals below 0.5 should be rounded down, and those equal to or greater than 0.5 should be rounded up to the nearest dB.

Figure 2.1 The “A-Weighted” Curve

The noise levels emitted by vehicles typically varies with frequency, and a typical relationship between noise level and frequency is shown in Figure 2.2.


NO

ISE

LEV

EL D

IFFE

RE

NC

E d

B

FEQUENCY Hz

-40

-30

-20

-10

0

+10

31 63 125 250 500 1000 2000 4000 8000 16000


Figure 2.2 Typical Noise Level - Frequency Relationship

Some examples of typical sound levels in dB(A) are shown in Figure 2.3 below. All further reference to noise levels in these Guidelines will be in dB(A).

Figure 2.3 The level of common sounds on the dB(A) scale


40

50

60

70

80

63 125 250 500 1000 2000 4000 8000

FREQUENCY Hz

NO

ISE

LE

VE

L d

B(A

)

140

120

100

80

60

40

20

0

Threshold of pain

Threshold of hearing

Communication starts becoming difficult

Hazard to hearing from continuous exposure

Quiet bedroom

Busy office

Car at 60 km/h, 7 metres away

Large truck at 40 km/h,7 metres away

Jet aircraft, 250 metres overhead

Freight train at 40 km/h,7 metres away


2.5 TYPES OF ROAD NOISEThere are two types of road traffic noise:

(a) from ‘bulk’ traffic flow (i.e. a reasonably continuous stream of vehicles), and

(b) from individual noisy vehicles.

The first occurs on busier roads and manifests itself as a continuous hum or backdrop of noise, although it can have peaks and troughs according to the traffic flow. It is the aggregate noise of all the vehicles in the traffic stream.

The second is produced by single vehicles (typically a high-revving motorbike, a car with a modified exhaust system, or a commercial vehicle’s exhaust brakes) and can occur anywhere and at any time. This may be loud enough to rise above bulk flow traffic noise and can be extremely disruptive, particularly at night in quiet residential areas where sleep can be disturbed.

Although measures can be taken to protect the community against both types, the second is by far the harder to deal with because of the random nature of occurrences, and can only be controlled by vehicle design requirements and in-service monitoring of these requirements. These Guidelines essentially deal with bulk flow traffic noise resulting from normal operation of the road system.

2.6 FACTORS INFLUENCING ROAD TRAFFIC NOISE GENERATIONIndividual vehicle noise is a combination of noises produced by:

the engine;

the transmission;

the exhaust;

the interaction of tyres and road pavement;

air turbulence; and

body and load rattles.

At lower traffic speeds (typically less than 60 km/hr), engine and exhaust noise tend to dominate. Tyre noise is a component of vehicle noise which significantly increases with speed. Studies suggest that at speeds between 30 and 50 km/hr, tyre noise of cars is increased to a level which dominates the overall vehicle noise. For trucks, this ‘cross-over’ point tends to occur between 40 and 80 km/hr.

Given the increasing stringency of vehicle design regulations on engine and exhaust emissions, tyre noise is increasingly becoming the major factor influencing overall traffic noise. The tyre noise component is highly dependent on tyre / pavement design and on vehicle speed. For heavy vehicles the exhaust outlet location is often elevated, which tends to increase the spread of noise. Air turbulence is not usually important, even at highway speeds.



Figure 2.4 Passenger car noise sources at speeds below 70 km/h (ARRB, 1998a)

27%

9%

30%

34% Exhaust Systems

Air Intake System

Tyres

Engine

Apart from individual vehicle noise, there are five main factors upon which the level of traffic noise depends:

traffic volume;

traffic speed;

traffic composition (i.e. the number of commercial vehicles);

the road gradient, and

the pavement surface type and texture.

A change in noise levels may occur if one, or more, of the above factors change. In addition, there are six major factors which influence the propagation of traffic noise:

the road profile (at grade, depressed or elevated);

the distance from the source to the reception point;

the nature of the ground between the source and the reception point;

the angle of view of the traffic stream from the reception point;

the presence of screening (by fences, earth mounds, barriers or buildings), and

meteorological effects, particularly wind strength and direction.

With the exception of the meteorological effects (refer Section 5.4.4), attention can be paid to all of the above factors in order to reduce the impacts of road traffic noise.



2.7 NOISE DESCRIPTORSThere are two descriptors commonly used to describe road traffic noise which varies over time. These are L10 and Leq.

The noise descriptor L10 refers to the noise level which is exceeded for 10% of the time in a given measurement period, and corresponds to the average of the upper noise levels. In Figure 2.5 below, which shows typical noise level variations over a one hour measurement period, L10 is the noise level which is exceeded for 6 minutes (10% of one hour).

The noise descriptor Leq (the equivalent noise level) refers to the value of a steady noise that would have the same acoustic energy as the varying noise, over the same time period. Figure 2.5 below also shows the Leq level.

The descriptor L10 is used by some organisations as the descriptor for traffic noise. The descriptor Leq has now replaced L10 as the commonly used descriptor. Generally, L10 is around 3 dB higher than Leq, although this difference varies.

Figure 2.5 Common Road Traffic Noise Descriptors.

NOISELEVEL

LIO

Leq

0.5 minutes 2 minutes

2 minutes

1.5 minutes

60 minutes

2.8 NOISE MITIGATION MEASURESThere are several ways in which the impacts of road traffic noise can be reduced, the main ones being (also Refer Figure 2.6):

(a) at the source, by controlling the noise emitted by the vehicle;

(b) along the transmission path, by reducing (attenuating) the noise level as it travels from the source to the reception point by providing intervening barriers or buffer zones; and

(c) at the reception point itself, by means of a barrier, building location and architectural design details to reduce the transmission of noise into the interior.



2.8.1 Noise control at the sourceNoise control at source is the most effective and equitable way of reducing the impacts of road traffic noise. This is accomplished by means of the relevant Australian Design Rules which stipulate the amount of noise various classes of new vehicles are permitted to emit under certain conditions. Although there are moves to make the rules more stringent, this can only be done slowly in line with progress in vehicle technology and the attendant cost penalties. Control at source is however, the most effective way of reducing both bulk flow noise and individual vehicle noise.

The Department participates in national forums which formulate and administer the Design Rules and actively encourage and support related research and development of quieter vehicles.

Other measures include travel demand management initiatives, ensuring the smooth flow of traffic by reducing vehicle stop / starts and adopting low noise pavement types.

2.8.2 Noise control along the transmission pathControl along the transmission path is the main way that traffic noise impacts can be reduced at a project level and it is to this area that these Guidelines are primarily directed. Measures include:

initial route location (away from houses etc);

providing distance between the source and the receiver within the road corridor such as wide areas of grassed or planted land to absorb noise. There is an inverse square relationship between sound intensity and distance. Noise will be reduced by 3 dB if the distance from the source is doubled;

placing the road in cut (where practical) to shield adjacent receivers from noise;

constructing mounds, barriers or fences to shield residences by creating ‘shadow zones’.

2.8.3 Noise control at the receiverControl at the reception point can be achieved by

locating and siting the building away from the noise source;

putting the more noise-sensitive rooms in the areas least exposed to the traffic noise; and

by architectural acoustic treatments such as thick or double glazing, solid doors, and noise insulation of ceilings, walls and floors.

Planning Authorities can reduce or avoid potential problems with traffic noise by means of the appropriate zoning of land adjacent to arterial roads, and through ensuring acoustic issues are addressed in development and building controls. Further information is available in Reducing Noise and Air Impacts from road, rail and mixed land use – A Guide for builders, designers and the community.



Figure 2.6 Ways of controlling traffic noise

(a) control at source

(b) control along transmission path

(c) control at reception point



3 ASSESSMENT PROCESS

3.1 SCOPE OR APPLICATION OF THE GUIDELINES3.1.1 Scope Definition

Minimising the impacts of road traffic noise should be an objective of any project involving the construction of new or substantially upgraded or redeveloped roads adjacent to noise sensitive receivers. A noise assessment (and potentially noise mitigation) as outlined in these Guidelines should normally be considered under the following circumstances.

New Road

Where a new road is built, where no road previously existed (eg Northern Connector)

Redeveloped Road

Where one or more lanes is added to an existing road, for the purpose of increasing the traffic carrying capacity of the road.

Where an existing road is realigned such that traffic is moved closer to sensitive receivers by at least one lane width (ie 3.0m), resulting in a ‘significant’ increase in received noise levels.

Where widening/ realignment of an existing road requires the demolition of building structures or existing roadside noise walls that results in receivers previously shielded from traffic noise becoming exposed.

Where realignment produces noise at a receptor from a different direction that makes a ‘significant’ contribution to existing noise (eg elevated section of South Road Superway).

Where the function of a road is changed, resulting in a ‘significant’ increase in received noise levels. For example, increasing the number of heavy vehicles by 50 per cent or more on the road where the works are located.

Noise treatment would not normally be considered in the following circumstances.

Upgrading or treating of road surfaces for maintenance, except where that road surface has been specifically placed as part of a noise treatment package, in which case a similar performing surface should be used.

Minor upgrading work such as realignment of an intersection, or creation of a left turn lane, unless it is part of a major upgrade.

Noise sensitive receivers located outside of the defined Noise Assessment Boundary to which these Guidelines are applied (Refer to Section 5.3).

Implementation of Hard shoulder running, where this is done for reasons other than increasing traffic carrying capacity (eg where the shoulder ‘lane’ is only operational during peak traffic times to reduce congestion)

3.1.2 Noise Sensitive ReceiversNoise sensitive receivers include:

Existing dwellings in a zone where dwellings are contemplated as defined by the relevant Development Plan;



Aged care facilities;

Hospital wards;

Caravan parks that accommodate existing long term residential use;

Churches/places of worship (where reasonable and practicable on a case-by-case basis);

The impact of traffic noise on parks should be considered on a case-by-case basis with protection considered for areas used for passive recreation; and

The impact of traffic noise on existing educational institutions, childcare centres and kindergartens should be assessed on a case-by-case basis for daytime criteria only and only to protect teaching areas. Teaching areas within schools may include an outdoor space provided there are no alternative quiet locations for that space.

3.1.3 Noise Catchment Areas and Grouping ReceiversNoise level predictions should be undertaken for each noise sensitive receiver. However, in relation to determining noise mitigation requirements, noise sensitive receivers may be considered on an individual basis or grouped where there is similar exposure to noise.

The intent of grouping receivers is to ensure a common assessment or mitigation approach for those receivers that have a similar exposure to noise to provide a more reasonable and practical approach.

Where individual receivers are grouped together, they are referred to as a Noise Catchment Area under these Guidelines. A noise catchment should include:

at least three noise sensitive receivers in close proximity; and

all receivers are exposed to similar noise levels (i.e. typically within 2 dB(A) of each other) and are usually at a similar proximity to the noise source; and

a logical delineation of the catchment area (e.g. by topography, cuttings, setbacks, road, rail or utility corridors, breaks in the landscape etc.).

When grouping noise sensitive receivers into a noise catchment area, the decision to investigate or provide noise mitigation should be based on the extent of criteria exceedances across the group. If mitigation is required, applying a consistent approach across the catchment and wider project is advised.

For example, if the predicted noise levels across a noise catchment area indicate compliance with the noise assessment criteria at more than two-thirds of receivers, and the remaining receivers have minor exceedances of 2 dB(A) or less, then no further noise mitigation is required to be considered. In a similar way, each storey and facade of a multi-storey apartment block may be considered individually or managed as a group. Further consideration should be given to any individual receivers that exceed the noise assessment criteria (refer Section 3.2) by more than 2 dB(A).

3.1.4 Responsibility for Mitigating Traffic NoiseThe Department is responsible for the provision of noise mitigation measures which protect developed noise sensitive receivers within the defined Noise Assessment Boundary for a new or redeveloped road project.

Noise mitigation measures will also be provided to protect any noise sensitive receivers for which a Development Consent under the Development Act 1993 has been granted before the date that the road project was publically announced.

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for developments submitted for planning approval after a road project has been publicly announced. Developments should comply with provisions in the relevant Development Plan and where applicable the requirements of the Minister’s Specification SA 78B.

3.2 NOISE ASSESSMENT CRITERIA3.2.1 Noise Descriptors

The noise descriptors in the table below refer to the energy averaged equivalent (Leq) noise level over each period, and are defined as:

Time Period Descriptor

Day (7am to 10 pm) dB(A)Leq (15hr) or LAeq day

Night (10pm to 7 am) dB(A)Leq (9hr) or LAeq night

3.2.2 Noise CriteriaThe following table sets out the Noise Criteria applicable for either ‘new’ or ‘redeveloped’ road projects (Refer Section 3.1.1). The application is also explained in Figure 3.1.

Project Type Applicable situationNoise Criteria(1) – dB(A)Leq

Day Night

New Road Existing receivers affected by noise from a new road 55 50

Redeveloped Road

Existing receivers affected by noise from a redeveloped road 60 55

Existing receivers affected by noise from a redeveloped road and where demolition of building structures or existing roadside noise walls(2) results in receivers previously shielded from traffic noise becoming exposed.

57 52

Note:

(1) Assessed at 1 metre from the facade (refer Section 3.2.5).

(2) Does not include property fencing.

Note that the redeveloped road criteria are reduced by 3 dB in situations where a sensitive receiver may experience a perceived increase in noise exposure due to the demolition of adjacent building structures or existing roadside noise walls (that are not replaced).

It is typically applicable in situations where the front rows of houses or an existing noise wall has been demolished to make way for the project, thereby exposing the rows behind to a further increase in noise. The reduced Noise Criteria is not applicable in situations where an existing property fence has been removed.



3.2.3 Relative Increase CriterionA large increase in existing noise can cause a major change to the acoustic environment of a location. Under these guidelines, this is assessed using a Relative Increase Criterion (RIC). The application is also explained in Figure 3.1.

The Relative Increase Criterion (RIC) should be applied to receivers where it is more stringent than the new or redeveloped road criteria (refer Section 3.2.2). This would generally only occur where a new road is being developed in an area where there is no or low levels of existing traffic noise. In this instance only the RIC needs to be applied to the receiver. Note that the lowest assessable existing noise level is 30 dB(A)Leq.

The most stringent criterion of either the day or night time period is applicable. The RIC is defined as:

Time Period Descriptor

Day (7am to 10 pm) Existing LAeq day + 12 dB

Night (10pm to 7 am) Existing LAeq night + 12 dB

3.2.4 Transitioning Between Noise Catchment Areas with Different CriteriaA criteria transition will need to be considered when a project spans across multiple noise catchments that have different noise assessment criteria. In these situations, the method of criteria transition can either be a gradual or immediate transition depending upon how logical the delineation of the noise catchment area is (e.g. delineation by topography, cuttings, setbacks, road, rail or utility corridors, breaks in the landscape etc.).

For example:

A local road extends perpendicular to a ‘redeveloped’ road project between two noise catchment areas, namely Catchment A and Catchment B. Catchment B has had the front row of houses demolished due to a shift in the road alignment, while Catchment A houses are untouched. In this case an immediate transition is likely to be the preferred approach i.e. where the Noise Criteria changes immediately from 55 dB(A) at Catchment A to 52 dB(A) at Catchment B.

A ‘new’ road project merges into a ‘redeveloped’ road project. In this case a gradual criteria transition from 50 dB(A) (New Road) to 55 dB(A) (Redeveloped Road) in 1 dB(A) steps is likely to be the preferred approach.

3.2.5 Noise Assessment LocationNoise levels are to be predicted or measured outside at a position one metre from the most exposed window at a height of 1.5 metres above floor level for each noise sensitive-receiver building facade. Noise levels at this location are influenced by reflections from the building facade, and all predictions are to include a facade reflection factor of +2.5 dB.

If noise levels for individual properties are measured at locations not subject to reflections from the building facade, they should also be subject to an adjustment factor of +2.5 dB to ensure that the comparison of noise levels against the noise assessment criteria are consistent. Each floor level of a multi-storey building should be considered separately when predicting noise levels for comparison against the noise assessment criteria.



3.2.6 When should Noise Mitigation be considered?Receivers with exceedances (or residual exceedances) of the Noise Criteria or Relative Increase Criterion (RIC) should be assessed as outlined below and in Figures 3.1 and 3.2 to determine if they are eligible for noise mitigation.

Noise levels and noise increases should be assessed at each affected receiver facade noting that the largest noise increase may not be at the noisiest facade.

The receiver’s eligibility for consideration of noise mitigation should be based on the change in noise level due to operational changes associated with the proposed road design at the project-opening year. For this comparison, it is important that project related noise barriers are not included, however road design measures such as road surface type and jersey barriers should be included.

Once a receiver is eligible for consideration of noise mitigation, the mitigation measures should then be designed to meet either the Noise Criteria or the RIC (whichever is the most stringent) for the predicted traffic volume 10 years post project opening, where reasonable and practicable.

When evaluating if a receiver is eligible (at the project-opening year), one of either the following tests must be satisfied:

(a) is the predicted noise level greater than the Relative Increase Criterion, if it is the most stringent noise assessment criteria (refer Section 3.2.3)?

(b) is the project predicted noise level more than 2 dB(A) (i.e. ≥ 2.1 dB(A)) above the existing predicted noise level for the same year (or an earlier year as elected by the project) and above the Noise Criteria?

(c) is the project predicted noise level greater than or equal to 5 dB(A) (i.e. ≥ 5.0 dB(A)) above the Noise Criteria?

The above tests provide for a reasonable and practicable approach to identifying eligible receivers through managing large relative increases in noise, high noise exposure situations, as well as small noise increases not perceptible to the human ear (i.e. less than 2 dB(A)).

3.2.7 Flowchart of Assessment ProcessThe flowchart provided on the following pages (Figure 3.1 and 3.2) outlines noise the assessment process to be undertaken under these Guidelines. It applies to each noise sensitive receiver as outlined in Sections 3.1.2 and 3.1.3.

Note that selecting the most reasonable and practicable noise mitigation measures may be an iterative process reflecting a mixture of treatment options.



Figure 3.1 Noise Assessment Criteria flow chart



Figure 3.2 Noise Mitigation flow chart



4 NOISE MITIGATION DESIGN

4.1 ROAD DESIGNRoad design measures may include adjustment to the vertical and horizontal alignments, low noise pavement surfaces, road gradient modifications, speed limit reduction, traffic management measures, New Jersey style barriers and the like.

These measures should only be implemented where there are no significant impacts on other road design considerations such as cost, access, security, community acceptance and safety.

Although the noise reducing road design measures are to be considered as the first stage of the acoustic assessment, they should be revisited during consideration of subsequent stages such as barrier design and house treatment determination. That is, the selection of the most cost effective mix of treatment is expected to require an iterative design process across all stages.

For example, when determining a barrier height, if further noise reduction is required to achieve a noise benefit, it may be more cost effective to change the pavement type than increase the barrier height. However when low noise pavement surfaces are used for noise attenuation there must be a commitment to continue the use of these surfacings in future maintenance of the road.

4.2 NOISE BARRIERSA guide to reasonable heights for roadside noise barriers and acoustic fences are detailed in the following table.

Proposed Barrier Location Height

Property boundary

Access to property is through the barrierUp to 2.4 with solid gates(1)

Property boundary

Property access is from another roadUp to 4m(2),(3)

Within road reserve Up to 7m(3)

Notes:

(1) Fences with gates may be constructed to a height above 2.1 metres as long as the gate is designed so as not to degrade the acoustic performance of the fence and the functionality of the gate is acceptable.

(2) Individual project circumstances may result in a project specific requirement to alter the height above 4m.

(3) Barriers that are greater than 3.5m in height must take into account factors such as the noise reduction benefit versus cost, practical construction limitations, visual amenity and overshadowing issues. Generally, these barriers should be set back from an adjacent property boundary taking into account the ability to maintain the space and the potential to reduce the impact of the barrier by using clear barrier material.



Where acoustic fences are to incorporate gates for access reasons, the fence should not normally be constructed to a height greater than 2.1 metres as the gate may degrade the acoustic performance of the fence and be difficult to open. However, a higher fence incorporating a gate may be constructed where it can be demonstrated that the gate will not degrade the acoustic performance of the fence and the functionality is acceptable (e.g. the gate is automated).

Safety aspects for access to the property, such as ability to open the gate with the vehicle off of the road should also be considered, i.e. situations that would present a danger for the resident to stop and exit a vehicle on an arterial road in order to open the gate manually.

4.2.1 Barrier DesignThis section describes the objectives/process to be used to design noise barriers for receivers that have been identified as eligible for consideration of noise mitigation under Section 3.2.6. The objectives to be considered during barrier design are as follows:

(a) Communities should receive reasonable and equitable outcomes.

(b) Noise mitigation should be designed to reduce noise levels to the criteria.

(c) Noise barrier evaluation processes must:

- Give preference to reducing outdoor noise levels and the number of property treatments.

- Provide efficient barrier heights and extents without disregarding lengths of effective noise barrier in front of eligible groups of receivers.

- The average barrier length per property should typically be restricted to 50 metres in recognition that appropriate property treatments (refer Section 4.2) for dwellings more than 50 metres apart represent a significantly more cost effective solution than the construction of a barrier.

(d) Noise mitigation should be evaluated and installed where reasonable and practicable.

Noise barrier designs can vary in height along the barrier length, subject to urban design and community views. However if a barrier is to vary in height along its length it must achieve an equivalent noise outcome for the community as a constant height noise barrier.

Before assessing barrier height the location of the barrier should be reviewed to ensure that it provides the best opportunity to use the topography and road geometry to maximise shielding.

4.2.2 Noise Barrier BenefitAs a guide noise walls or mounds are considered to be a reasonable noise mitigation option where they are capable of providing an insertion loss of:

For noise barriers more than 3 m high, the insertion loss must be more than 5 dB(A) at the most affected receiver, or

10 dB(A) at representative receivers for heights above 5 metres and up to 7 metres high.



When considering the above insertion loss requirements, the following provides additional clarification:

Where a location exceeds the noise assessment criteria by less than 5 dB(A) this could lead to designing to achieve an insertion loss of less than 5 dB(A). Under these circumstances, where two-thirds of the noise sensitive residences no longer require property treatment a noise barrier should not be abandoned because it did not provide 5 dB(A) insertion loss.

Small barriers that are low cost to install, such as jersey barriers, but do not provide an insertion loss of 5 dB(A), may also form part of an overall noise mitigation strategy.

Where noise barriers greater than 5 metres in height do not provide 10 dB(A) of noise reduction, additional consideration needs to be given to the number of receivers that benefit, any unusual topography and whether the barrier placement could be improved. If it is not reasonable to provide a barrier with height above 5 metres then lower heights should be considered.

4.2.3 Barrier MaterialsA noise barrier should generally be constructed from the most cost effective materials that will not significantly degrade the acoustic performance of the barrier. In relation to residential fences the material should generally be Colorbond or equivalent or if there is an existing fence it should be replaced with similar materials to existing. However, other criteria such as maintenance, longevity, existing fencing, amenity, urban design and streetscape issues, Council requirements in relation to the character of the area and heritage issues may also need to be considered in the material selection process.

It may be possible for individual land owners to upgrade the barrier construction on their property, over that offered by the Department, by paying the difference in cost, provided that the acoustic performance is not compromised.

Refer to the Noise Mitigation Manual for more information on acceptable barrier materials.

4.2 PROPERTY TREATMENTThis section describes the various property treatments that may be used to treat receivers that have been identified as eligible for consideration of noise mitigation under Section 3.2.6. Property noise mitigation measures may replace road corridor mitigation, subject to a reasonable and practicable assessment, and only in the following circumstances:

Isolated single residences or isolated groups of closely spaced residences.

Where the affected community expresses a preference for at-property treatment and the cost is less than a combination of a barrier and at-property treatment.

Where noise barriers cannot achieve the level of noise mitigation (insertion loss) required.

Where other noise mitigation measures have been shown not to be reasonable or practicable.



These treatments are generally limited to facade treatments to habitable spaces. However on a case-by case basis the installation of acoustic screening close to the dwelling may be considered in lieu of facade treatments.

4.3.1 Facade Treatment Criteria Under these guidelines, facade treatments to habitable spaces relate to National Construction Code (NCC) Class 1, 2, 3 and 4 buildings and 9c aged care buildings (refer to Appendix A for NCC building classifications). Note that transportable buildings are not eligible for treatment unless it can be demonstrated that upgrade of the facade glazing is likely to result in a noticeable noise reduction for the resident.

Noise sensitive receivers that do not fall under the NCC categories are typically assessed on a case-by-case basis (e.g. educational institutions or hospital wards). In these instances, the current revision of Australian Standard AS 2107 – Acoustics – Recommended design sound levels and reverberation times for building interiors may be referred to as the basis for acoustic design.

If receivers have been identified as eligible for consideration of noise mitigation under Section 3.2.6, the facade treatment package is determined from the table below.

Habitable SpaceApplicable Facade Treatment Package for Noise Levels above the Noise Criteria or Relative Increase Criterion

>2 - 5 dB(A) 6 - 9 dB(A) 10 - 13 dB(A) >14 dB(A)

Bedrooms 1 2 3 4

Other habitable rooms n/a 1 2 3

Notes:

(1) Predictions must be at 1 metre from the facade, include the 2.5 dB(A) facade reflection correction and rounded to the nearest decibel to ensure correct determination of the Sound Exposure Category.

(2) For Facade Treatment Package 3 and 4, alternative ventilation in addition to openable windows must be provided in accordance with the requirements of Section 4.3.4.

(3) Non-habitable rooms include walk-in wardrobes, en-suites and enclosed kitchens. However, where these spaces are part of an open plan arrangement with adjoining habitable rooms, such as a living/dining area or bedroom, they need to be treated as part of the habitable room.

(4) Treatments to residential dwellings will be restricted to bedrooms, studies, living, dining and kitchen areas that have windows or doors in the façade being treated. Corridors, laundries, bathrooms, garages, sheds and workshops will not be treated.

(5) When the Noise Criteria is less than 50 dB(A), treatments to residential dwellings will be restricted to bedrooms that have windows or doors in the façade being treated.

For example, if the predicted outdoor noise level at 1 metre from the most exposed facade is 63 LAeq night, the Facade Package Treatment for a redeveloped road criteria of 55 dB(A) is ‘2‘ for bedrooms and ‘1’ for other habitable rooms.



4.3.2 Facade Treatment PackagesThe following table outlines the applicable Facade Treatment Package with reference to the applicable package number obtained from Section 4.3.1.

Note that the Facade Treatment Packages are a deemed to satisfy solution to meet the requirements of these Guidelines. An alternative solution is not required to be designed by an acoustic engineer. However, an acoustic engineer may design alternative treatment options to achieve an equivalent acoustic performance to the specified package treatments.

Facade Treatment Package

Acoustic Performance Requirements

1

Windows and external glass doorsWindow = RW + Ctr 31

For example, the acoustic equivalent of an existing window system incorporating 3 mm thick glass, with the addition of a 4.5 mm thick acrylic panel separated by a 150mm air gap or a single window system incorporating at least 6 mm thick laminated glass.

Door = RW + Ctr 28

For example, the acoustic equivalent of a glass door system incorporating at least 6 mm thick laminated glass.

Acoustic Seals

In order to achieve the acoustic performance, acoustic grade seals will need to be incorporated into the above secondary or replacement window or door systems.

External doors other than external glass doorsDoor = RW 30

For example, the acoustic equivalent of a solid timber core door with acoustic grade seals to head and jamb.

External Flanking PathsInspect the facade for external noise flanking paths that could potentially degrade the installed treatment. Rectify where reasonable and practicable. For example, block internal wall vents that have a direct path to the external wall facade. Note that external wall or floor cavity vents required for moisture control do not need to be treated.



Facade Treatment Package

Acoustic Performance Requirements

2


For example, the acoustic equivalent of an existing window system incorporating 3 mm thick glass, with the addition of a 10 mm thick acrylic panel separated by a 100 mm air gap or a single window system incorporating at least 10 mm thick laminated glass.

Door = RW + Ctr 31

For example, the acoustic equivalent of a sliding glass door system incorporating at least 10 mm thick laminated glass.

Acoustic Seals

In order to achieve the acoustic performance, acoustic grade seals will need to be incorporated into the above secondary or replacement window or door systems.


For example, the acoustic equivalent of a solid timber core door with acoustic grade seals to head and jamb.


3


For example, an acoustically rated single or double-glazed window system that can achieve the acoustic performance requirement. It is likely that a new window system will be required.

Door = RW + Ctr 34

For example, an acoustically rated single or double-glazed door system that can achieve the acoustic performance requirement. It is likely that a new door system will be required.

Acoustic Seals

In order to achieve the acoustic performance, acoustic grade seals will need to be incorporated into the window or door system.



3 (cont.)


For example, the acoustic equivalent of a solid timber core door of not less than 28 kg/m2 surface density, acoustic grade seals around the head and jamb acoustically equivalent to Kilargo IS1212/1515 or Raven RP120/150 (batwing seals) and a dropdown seal at the bottom acoustically equivalent to Kilgaro IS8090si or Raven RP38.

Double doors to also have meeting stile seals acoustically equivalent to Kilargo 2xIS7060si or IS7071si, or Raven 2xRP16 or 2xRP71Si.

Roof and CeilingProvide insulation batts to ceiling cavity if no insulation present on inspection.


VentilationMechanical ventilation is required in accordance with Section 4.3.4 and should be designed such that the facade acoustic performance is not degraded.

4Package 3 architectural treatments (above) are applicable. An offer for voluntary acquisition of the property may also be considered on a case-by-case basis.

The following should be considered before and during the application of facade treatments:

Only facades of habitable rooms being used at the time of the project will be treated. Future renovations (not yet approved by Council) that will change the use of a space will not be considered during the treatment process.

Facades of rooms that are not habitable and/or in a considerable state of disrepair will not be treated.

Facades that contain asbestos can be treated under the provision that the owner pays for cost of asbestos removal and clean up.

Electrical wiring that is considered not safe to supply a mechanical ventilation system can be repaired at the owners cost.

Architectural treatments may be substituted with alternative treatments at the discretion of Departmental representatives, where the alternative provides an equivalent level of noise reduction.

While due care must be taken in the design and selection of acoustic treatments the Department makes no guarantee that any particular internal noise level will be achieved.



4.3.3 Facade Treatments to Noise Sensitive Non-Habitable SpacesNoise sensitive non-habitable spaces relate to educational institutions, childcare centres and kindergartens. Facade treatments to these receivers will be determined on a case-by-case basis using AS/NZS 2107:2000 (or current issue).

4.3.4 Mechanical VentilationThe provision of mechanical ventilation is required to be considered for Facade Treatment Packages 3 and 4, where no suitable existing mechanical ventilation exists.

Note that mechanical ventilation is not required for Facade Treatment Packages 1 and 2, although may be provided at the discretion of the Department where it is required under the Building Code.

Where a mechanical ventilation system is required, the ventilation system must be installed:

(a) In accordance with the Building Code of Australia and complying with AS 1668.2 - The use of mechanical ventilation and air-conditioning in buildings, and

(b) The relief air path/s should be fully ducted to allow operation of the system with windows and external doors closed, and

(c) The fresh air (or make up air) inlets and exhaust air outlets shall be at a point on the building furthest from the road corridor where practicable.

4.3.5 Acoustic ScreeningAs an alternative to facade treatments (for eligible receivers), property treatments can also utilise acoustic screening situated close to the dwelling for the purpose of shielding an outdoor entertainment area (and associated facade) if this is considered a preferred approach. Acoustic screening is considered on a case-by-case basis where practical and in consultation with the resident.

Acoustic screening should be treated in the same way as a property boundary fence in terms of height limits, materials and value for money insertion loss performance.

4.3 NOISE MITIGATION GENERAL NOTES Under no circumstances will the Department offer monetary compensation to

property owners instead of noise mitigation treatments.

A property owner can reject offered noise mitigation treatments but must sign a Statement of Agreement to Refuse Noise Mitigation Treatment.

Alternative treatments providing less acoustic attenuation may be provided where the property owner prefers the alternative and understands they will not be provided with an equivalent level of noise mitigation. In this case, a waiver must be signed by the property owner. Refer to the Noise Mitigation Manual for information on suitable alternative treatments.

Mitigation treatments should consist of constructions and materials that are deemed by the Department to be reasonable and practicable. If the property owner desires an alternative construction or material, any additional cost will be the responsibility of the owner.



5 PROCESS FOR ASSESSING ROAD TRAFFIC NOISE

5.1 GENERALNoise impacts and mitigation measures need to be identified and implemented throughout the project delivery process from the initial strategic and concept planning stages through to design and construction. Noise mitigation should be considered as an integral part of the planning and design process and not an “add-on” once the preferred solution has been developed.

For the ground floor residential dwellings that are eligible for consideration of noise mitigation measures, mitigation should be designed such that future traffic noise levels (10 years from opening) achieve the Noise Criteria where reasonable and practicable. Where it is not reasonable and practicable to achieve the criteria, Facade Package Treatments to the individual dwelling should be provided in accordance with the process outlined in Section 4.3.

For the upper floors of any multi-story residential building, only facade treatments will be considered. For non-residential noise sensitive receivers, where the property is not normally used at night times, only the day time criteria need be applied.

Mitigation measures should protect exposed building facades and areas likely to be used for outdoor entertainment. They would not normally be provided to protect areas primarily used for parking or storage.

The process for assessment of road traffic noise is outlined below:

(a) publicly announce the road project (if this has not been done already);

(b) obtain the project road design and identify traffic noise variables – this includes data on pavement surface type, gradients, traffic volume and composition (both day and night), traffic speed, traffic control devices and adjacent property details;

(c) predict the existing road traffic noise levels and compare to noise logging results representative of the existing traffic noise environment. From this, validate the noise model using known corrections to adjust for Australian conditions. Calibrate the noise model as required in consultation with the Department or representatives. Calibration corrections from previous project verification assessments should also be considered where available;

(d) predict the future existing road traffic noise levels at the project-opening year;

(e) predict the future project road traffic noise levels at the project-opening year without any project related noise barriers;

(f) determine the Noise Assessment Boundary in accordance with Section 5.3;

(g) identify all noise sensitive receivers within the Noise Assessment Boundary and compare the predicted noise level differences between the existing and project model situations at the project-opening year and identify those noise sensitive receivers that are eligible for consideration of noise mitigation (refer Section 3.2.6);

(h) group into noise catchment areas where relevant (i.e. groups of receivers with similar noise exposure);

(i) predict the future project traffic noise levels (10 years into the future) and design reasonable and practicable noise mitigation measures in accordance with Section 4 and Section 5.5.1 based on this modelling scenario;



(j) for a planning and concept design phase assessment, document the noise assessment in the Planning Assessment Report, Environmental Report or Environmental Impact Assessment Report. Note that the documentation of noise mitigation during this phase should be focused on non-specific treatment options to allow design flexibility during the detailed design and construction phase of a project;

(k) for a detailed design and construction phase assessment, a Noise Mitigation Plan should be prepared that is suitable for consultation with the wider project team, Councils, the community and other key stakeholders with an interest on the proposed noise mitigation strategy. The Noise Mitigation Plan should then be refined over the detailed design phase until it is approved for Issue For Construction (IFC);

(l) post construction, verification of the noise model predictions and implemented noise mitigation measures should be carried out in accordance with Section 5.7.

5.2 PUBLIC ANNOUNCEMENT OF A ROAD PROJECTFor purposes of establishing whether a noise sensitive receiver should receive noise mitigation measures as part of a road project it is necessary to establish if the development of the land use has received development consent under the Development Act 1993 prior to the public announcement of the road project. Therefore, the Department should publicly announce the road project should be given by the Department at an appropriate stage in the planning phase.

Public announcement may entail a media release and/or contacting affected property owners/ stakeholders.

5.3 NOISE ASSESSMENT BOUNDARYThe extent of the Noise Assessment Boundary is defined as follows:

The location (project footprint) in which physical works associated with the road project occur and may extend to close-by landmarks or cadastral boundaries to provide a logical endpoint. Note that physical works does not include pavement reseals, or discrete elements of the project that fall outside the scope of the guidelines (as described in Section 3.1.1).

The width either side of the project is to be set to the extent where the predicted noise level without noise mitigation equals the lowest applicable noise assessment criteria. Note that the width may be reduced where the noise levels from the project contribute no more than 2.0 dB(A) to the total traffic noise level, for example, where the assessed road project intersects other Arterial Roads.

In any case, the width either side of the project should be no more than 600 meters from the centre line of the outermost traffic lane on each side of the road project. This distance is based on the limit of accuracy of current road traffic noise models.

The Noise Assessment Boundary should be defined using property boundaries obtained from a current cadastral map.



5.4 MODELLING ROAD TRAFFIC NOISEAn appropriate road traffic noise prediction software package that is acceptable to the Department must be used for all road traffic noise assessments. The Department will accept the use of software that correctly implements the United Kingdom, Department of Environment (1988), Calculation of Road Traffic Noise (CoRTN) algorithm. Other models such as the US Department of Transportation, Federal Highways Administration (FHWA) Traffic Noise Model (TNM) may also be used upon agreement with the Department.

Details of any modelling assumptions including the model calibration or verification procedure must be included in relevant project documentation.

5.4.1 Noise Model ValidationValidation of the noise model is considered good practice by the Department. This can be achieved by comparing the measured versus predicted noise levels determined at a number of representative sites for an existing situation noise model. The model may be deemed to be validated if the average difference between the measured and predicted levels is no more than ± 2 dB(A). Any calibration (or correction) factors used in the modelling process must be clearly documented.

5.4.2 Noise Model inputsTo undertake a detailed investigation, the following information is generally required, although the requirements will depend on the calculation algorithm being used:

(a) Traffic flow counts / predictions: The predicted Annual Average Daily Traffic (AADT) flows for the project and relevant surrounding road network is required. The AADT data must be separated into the volume percentage occurring over 7 am to 10 pm (day) and 10 pm to 7 am (night), for the existing conditions, at project-opening ‘no build’ and ‘build’ scenarios and 10 years future from project-opening. Furthermore, the traffic flow percentage splits for the following classifications are also required:

- Light vehicles (Austroads Classes 1 – 2)

- Heavy Vehicles (Austroads Classes 3 – 12)

(b) Traffic flow control devices: Details and location of any flow control devices are required. These may include stop signs, traffic signals, and on-ramp start points.

(c) Traffic speeds: Statutory sign posted speeds are preferred. Non-statutory speeds may be used in special circumstances upon agreement with the Department.

(d) Road design: Details of the road alignment and structures (i.e. bridge, underpass, jersey barriers etc) in x,y,z CAD format such as DXF, DWG, SHP.

(e) Topographical features: Details of relative heights, buildings, and landform etc. are required to carry out the noise predictions.

(f) Property identification: An identification number for all properties within the Noise Assessment Area will generally be issued by the Department’s property group.

(g) Pavement surface type: Pavement surface type is an important factor in determining overall traffic noise levels, with different surface types resulting in either increased or decreased noise levels. Guidance should be sought from Section 5.4.3 and agreed in consultation with the Department.



5.4.3 Road surface correctionsThe following table details typical values of noise level corrections for different road surface types, relative to dense graded asphalt. Note that the values in the table should be used as a guide only, as variations in road texture and porosity may affect the actual result achieved.

Surface type Increase (+) / decrease (-) in traffic noise level relative to DGA

Spray seal, 10 mm or larger + 4 dB

Spray seal, 7 mm or larger + 2 dB

Dense graded asphalt (DGA) 0 dB

Stone mastic asphalt (SMA) - 1 dB

Open graded asphalt (OGA) - 2 dB

For more information on the acoustic performance and durability of alternative road surfaces, including concrete road surfaces, refer to the Noise Mitigation Manual.

5.4.4 Meteorological EffectsModelling the effects of various meteorological conditions is not a requirement for traffic noise predictions, particularly given the capability of current traffic noise calculation algorithms. Noise predictions under these Guidelines are indicative of the average traffic noise received over an annual period.

5.5 DEVELOPMENT OF A NOISE MITIGATION PLANShould noise modelling of the proposed road design during the design and construction phase of a project indicate the consideration of noise mitigation, the development of a Noise Mitigation Plan (NMP) is required.

The NMP should clearly outline the Noise Assessment Area, all noise sensitive receivers, identified noise catchment areas, and the preferred combination of noise mitigation measures adopted for the project.

5.5.1 Reasonable and Practicable MitigationFor all road projects where noise mitigation measures are proposed, it is necessary to consider what measures are reasonable and practicable. Noise mitigation can be provided in a range of ways and may be a combination of methods including barriers, dwelling treatments and road design measures. The mix of treatments should be optimised and considered the most cost effective for the location.

Selecting reasonable mitigation measures from those that are possible involves judging whether the overall noise benefits outweigh the overall adverse social, economic and environmental effects, including the cost of the measure.



To make such a judgement, consideration may be given to:

(a) Cost: the cost of installing the mitigation measure, including the cost of materials, ongoing maintenance costs and any other costs likely to be incurred in scoping and installing the measure. The cost per dB noise reduction (or insertion loss) is an important indicator when weighing up the reasonableness of a noise mitigation measure, and measures that provide no noise reduction benefit should be avoided.

(b) Type of noise mitigation: consideration of the type of noise mitigation measure. For example, where practical it is preferable to reduce noise at the source (e.g. using road design measures) or minimise the transmittal of the noise (e.g. through road side noise barriers) rather than treat noise at the receiver through property fencing or architectural treatments.

(c) Community acceptance: before noise mitigation measures are finalised, the community’s views should be established and taken into consideration (refer Section 5.5.2).

(d) Urban design objectives: consideration of the visual impact, or benefits, of the noise mitigation measure, as well as shading, safety and security aspects.

(e) Environmental effects: noise mitigation measures such as roadside barriers and earth mounds can have environmental impacts themselves which may affect areas of cultural significance such as heritage buildings, areas of scenic beauty, local views or significant vegetation.

(f) Noise Catchment Area approach: refer Section 3.1.3.

The practicability of a mitigation measure relates to engineering considerations of what can feasibly be constructed and installed:

(a) Structural: consideration of issues for the noise wall design and installation issues, including wind, ground conditions etc.

(b) Access: any impacts that the mitigation measure may have on access to properties and/or to local roads.

(c) Safety: safety concerns associated with the mitigation measure. For example, road safety design requirements (i.e. clear zones, sight distances etc.), CPTED issues and pedestrian safety.

(d) Maintenance: consideration of the amount of upkeep needed to maintain the mitigation measure.

5.5.2 Community AcceptanceRoadside noise barriers or property boundary fences are frequently the most effective acoustic treatment as they provide protection to outdoor as well as internal living areas. However in order to achieve the criteria, they might need to be large and out of proportion to the built environment and so significantly impact upon the aesthetic amenity of an area.

Barriers and fences may also prevent residents enjoying a particular view. Certain works, such as high domestic fences, might not be permitted by the local planning authority.

Before noise mitigation measures are finalised for a project, consideration of the viewpoints of the property owners and residents that will receive a noise reduction benefit is required.



In the case of high property boundary fences, this should involve individual discussions with property owners after the development of a proposal for each property, which takes account of relevant streetscape, urban design and property issues. Mitigation measures with most support from the community should ideally be adopted where reasonable and practical.

5.5.3 Noise Mitigation PlanOnce the preferred combination of project noise mitigation measures has been selected, it should be clearly justified and documented in the NMP and associated Community Engagement Strategy.

A coordinated approach to property inspections and treatment installation is essential to minimise disruption and ensure efficient use of time and resources. Guidance on the process for inspecting properties and selecting, specifying and installing property treatments (including a suggested flow chart) is provided in the Department’s Noise Mitigation Manual.

5.6 DATABASE OF NOISE MITIGATION TREATMENTSA record of noise treatment including noise walls, fences and property treatments should be kept to assist in responding to any future queries about the work undertaken, and as a record of the extent of the arterial network with noise mitigation measures.

The Environmental Group in Asset Management - Technical Services manages this database.

5.7 POST CONSTRUCTION VERIFICATIONFor major projects, post construction noise monitoring by a suitably qualified acoustic engineer should be undertaken to verify the noise modelling predictions and the implemented noise mitigation measures.

Noise monitoring should be conducted once traffic flows have stabilised, and preferably within 6 months of project opening. Monitoring of traffic flows and composition should be undertaken simultaneously with the noise level monitoring. Care should be taken to locate the noise loggers used for verification away from the traffic counters to minimise tyre noise influence associated with travelling over the counter wire.

If the results are consistent with the predicted noise levels for the project opening year then it can generally be expected that the predicted noise levels for future years will also be achieved, and further monitoring is not considered necessary.

If post construction monitoring reveals that actual noise levels are higher than predicted noise levels at project opening year, the modelling shall be reviewed and further mitigation provided as required to achieve compliance with the criteria.

Model calibration factors derived and validated as part of the verification process should be provided to the Department for record keeping, as this information can be a valuable resource to inform future projects.


http://dpti.sa.gov.au/standards/environment?result_40034_result_page=1

http://dpti.sa.gov.au/standards/environment?result_40034_result_page=1


6. BIBLIOGRAPHYARRB Transport Research Ltd (1998) Road Surface Characteristics and Condition: Effects on Road Users. Research Report ARR314.

ARRB Transport Research Ltd (1998) Overview of Noise and Spray Durability Characteristics for Open Graded Friction Course.

Australian Building Codes Board, National Construction Code Series Volume One andTwo (Building Code of Australia)

Austroads (2003) AP-G63 03 Guide to the Selection of Road Surfacings.

Austroads (2005) APR277/05 Modelling, Measuring and Mitigating Road Traffic Noise

Berglund, B; Lindvall T, Schwela D, Goh KT (1999) World Health Organization: Guidelines for Community Noise

Department of Planning, Transport and Infrastructure (2010) Noise Mitigation Manual

Department of Planning, Transport and Infrastructure (2013) Minister’s Specification, SA 78B, Construction Requirements for the Control of External Sound

Department of Planning Transport and Infrastructure (2013) Reducing noise and air impacts from road, rail and mixed land use – a guide for builders, designers and the community

Department of Planning Transport and Infrastructure Reducing Transport Noise Impacts – A Guide to Home owners

Environment Protection Authority (1993) Environment Protection Act

Environment Protection Authority (2013) Guidelines for the assessment of noise from rail infrastructure

Kotzen, B. and English, C. (2009) Environmental Noise Barriers: A Guide to Their Acoustic and Visual Design, 2nd Edition

Standards Australia (2000) AS 2107 Acoustics – Recommended Design Sound Levels and Reverberation Times for Building Interiors.

UK Department of Environment (1988) Calculation of Road Traffic Noise

US Department of Transportation Federal Highway Administration (2010) Highway Traffic Noise: Analysis and Abatement Guidance.

World Health Organisation, 2009, Night Noise Guidelines for Europe, World Health Organisation, European Region



APPENDIX AClassification Summary of Buildings and Structures as defined under the Australian Building Codes Board (ABCB) National Construction Code.

CLASSES OF BUILDING

Class 1 Class 1aA single dwelling being a detached house, or one or more attached dwellings, each being a building, separated by a fire-resisting wall, including a row house, terrace house, town house or villa unit.

Class 1bA boarding house, guest house, hostel or the like with a total area of all floors not exceeding 300m2, and where not more than 12 reside, and is not located above or below another dwelling or another Class of building other than a private garage.

Class 2 A building containing 2 or more sole-occupancy units each being a separate dwelling.

Class 3

A residential building, other than a Class 1 or 2 building, which is a common place of long term or transient living for a number of unrelated persons. Example: boarding-house, hostel, backpacker’s accommodation or residential part of a hotel, motel, school or detention centre.

Class 4 A dwelling in a building that is Class 5, 6, 7, 8 or 9 if it is the only dwelling in the building.

Class 5 An office building used for professional or commercial purposes, excluding buildings of Class 6, 7, 8 or 9.

Class 6A shop or other building for the sale of goods by retail or the supply of services direct to the public. Example: café, restaurant, kiosk, hairdressers, showroom or service station.

Class 7Class 7a A building which is a car park.

Class 7b A building which is for storage or display of goods or produce for sale by wholesale.

Class 8A laboratory, or a building in which a handicraft or process for the production, assembling, altering, repairing, packing, finishing, or cleaning of goods or produce is carried on for trade, sale or gain.

Class 9

A building of a public nature:

Class 9a A health care building, including those parts of the building set aside as a laboratory.

Class 9bAn assembly building, including a trade workshop, laboratory or the like, in a primary or secondary school, but excluding any other parts of the building that are of another class.

Class 9c An aged care building.


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