Frequently asked questions about noise and vibration

Noise is often defined as unwanted sound. Sound sources cause changes in air pressure (sound waves), which are detected by our ears.

Sound waves can also be measured by a sound-level meter. The level (loudness) of the sound is expressed in decibels, abbreviated as ‘dB’.

Sounds are usually quite complex: their level changes over time and they have different frequency components. For noise levels to be comparable with each other and with limits we use standardised methods to calculate ‘average’ noise levels. The figure below shows typical average noise levels (in dB) for various situations and activities.

Typical sound levels in decibels (as experienced by someone participating in the activity, or at the specified distance from it

Noise can occur across a wide range of frequencies (pitch), from low-pitched rumbles such as thunder, to high-pitched squeaks and squeals. Most noises contain multiple frequencies all at once, which is often called ‘broadband’ noise.

The frequency content of sound waves is defined using the unit Hertz (abbreviated Hz), which is the number of ‘cycles per second’. People with very good hearing can hear frequencies within the range 20 Hz to about 20,000 Hz.

Our hearing is most sensitive to a middle range of frequencies associated with the pitch of human voices (about 500 Hz to 5000 Hz). We are much less sensitive to very low and high frequencies within our hearing range. To ensure that measured noise levels are comparable to the human experience of sound, we apply an adjustment to the measurement, called an ‘A-weighting’.

Noise levels fluctuate over time so noise is usually quantified in terms of an average noise level. An ‘energy average’ is used, which tilts the average in favour of the louder noises within the measurement period. This is average noise level is called an L_eq level (pronounced 'L E Q').

The time period over which the noise has been averaged is important and is stated alongside the level in decibels. For construction noise, L_eq values are typically assessed over a time period of 15 minutes. For road traffic noise the time period used in New Zealand is 24 hours.

When noise levels are reported, the level in dB will be followed by a descriptor (starting with L) of the type of measurement.

For example:  55 dB L_Aeq(24h)

• The measured average level is 55 dB.
• The L tells us this is an acoustic noise level (decibels are used for non-acoustic applications too, such as electronics).
• The subscript A shows that the A-weighting frequency adjustment has been applied.
• The subscript eq means this is an energy average sound level (‘eq’ stands for equivalent continuous sound level).
• The time in parentheses indicates the measurement duration, in this case 24 hours.

The measured maximum noise level from an activity has its own descriptor, L_max (pronounced L max). This is the maximum noise level that was encountered during the measurement duration, even if only momentarily (eg for less than a second). When maximum noise levels in dB are reported they will be followed by L_AFmax (sometimes abbreviated L_max or L_Amax).

For example: 90 dB L_AFmax

• The measured maximum level is 90 dB.
• The L tells us this is an acoustic noise level.
• The subscript A shows that the A-weighting frequency adjustment has been applied.
• The subscript F shows that ‘fast’ time-averaging was used (125 milliseconds).
• The subscript max denotes this as a maximum sound pressure level.

The figure illustrates average (L_Aeq(60min)) and maximum (L_AFmax) levels over a 60-minute measurement duration.

All noise levels are measured in ‘dB’ followed by a descriptor that explains what the measurement represents. If a noise level is followed by L_Aeq it is an average, and if it is followed by L_AFmax it is a maximum level.

L_eq and L_max are the main metrics used for road, rail, and construction noise, but there are many more in occasional usage. A noise metrics tool has been developed to indicate the values of different metrics based on an input noise level and road type.

Noise metrics tool

See NZS 6801:2008 Acoustics – measurement of environmental sound for further information on noise metrics.

NZS 6801:2008 Acoustics – measurement of environmental sound(external link)

As noise propagates (travels) from source to receiver, both its level (in dB) and its frequency content change.

There are a number of factors that affect the degree of change including distance, ground absorption, meteorological effects, and the extent of natural or constructed screening between the source and receiver.

Distance

As a general rule, road noise levels tend to decrease by about 3 dB for each doubling of distance from the road (and increases by 3 dB for each halving of distance). In other words, the relationship between noise level and distance is non-linear. For example, moving from 10m to 40m from the road the reduction is approximately 6 dB, but if moving from 110m to 140m from the road (that is, also by 30m) the reduction is only 1 dB.

Ground absorption

The type of ground cover between a noise source and a receiver can have an additional large effect on the noise level. Acoustically ‘hard’ surfaces, such as car parks or lakes, reflect sound and will not normally reduce the noise level. By contrast, acoustically ‘soft’ surfaces, such as loose dirt, grassland, or bush, can provide a quite a large noise level reduction (in the region of -5 dB over 50m).

Meteorological conditions

Meteorological conditions (wind, temperature, humidity and rain) can either increase or decrease the propagation of noise. These conditions have little influence close to the road, but become very significant over long propagation distances (say beyond 100 metres). Downwind propagation of noise and temperature inversions can improve propagation, and increase noise levels. Being upwind from a road can reduce the noise level. Given the lack of control over meteorological conditions, most noise models assume moderately enhanced propagation (eg downwind) as the basis for prediction. NZS 6801:2008 provides further detail on this subject.

NZS 6801:2008 Acoustics – measurement of environmental sound(external link)

Screening

The topography and natural terrain between a source and receiver can act as a shield or screen. This reduces noise levels by restricting the direct transmission of noise and by absorbing some of the noise. Features such as buildings, barriers, walls, embankments and bunds can also provide screening from noise in the same way as natural features. Depending on the alignment of a road and the site geometry, the first row of houses or buildings next to a road may offer screening from noise to second and subsequent rows.

Vibration is when an object or surface moves back-and-forth (oscillates) rapidly. ‘Vibration magnitude’ describes how much it moves, and ‘vibration frequency’ describes how fast it moves.

Whereas noise is something you hear, vibration is something you feel. The distinction can get complicated because loud noises can cause things to vibrate (eg loud exhausts can shake windows) and vibration can cause objects to wobble and make noise (eg rattling ornaments due to a passing train). The latter scenario is often called ‘ground-borne noise’.

Ground vibration can be generated through construction of roads and surrounding infrastructure, and to a much lesser extent in operation, by the passing of vehicles.

Vibration magnitude can be quantified in several different ways depending on the application or the type of measurement instrumentation used. Acceleration (in mm/s2) and displacement (in mm) are valid ways of quantifying vibration magnitude; however, for road-traffic- and construction-induced ground vibration, it is most common to use vibration velocity in mm/s.

Often the velocity is the peak particle velocity (PPV), which is the instantaneous maximum velocity of the vibrating surface (BS 5228-2 and DIN 4150-3 use this metric). NS 8176 uses a statistical maximum weighted velocity, v95, which is not directly comparable with PPV. Root-mean-squared (rms) may also be used.

BS 5228-2:2009+A1:2014 Code of practice for noise and vibration control on construction and open sites – vibration(external link)
DIN 4150-3:2016-12 Vibration in buildings – part 3: effects on structures(external link)
NS 8176:2017 Vibration and shock – measurement of vibration in buildings from land-based transport, vibration classification and guidance to evaluation of effects on human beings(external link)

The frequency of vibration is defined in Hertz (symbol Hz). The frequency range most relevant to transport-induced ground vibration is 1 Hz to 200 Hz.

Noise limits for construction work are generally set within designation conditions for road projects.  Most projects adopt one of the sets of suggested limits from New Zealand Standard NZS 6803:1999 Acoustics – construction noise. Waka Kotahi manages and minimises potentially unreasonable noise effects during construction activities (as far as practicable) in accordance with this standard.

NZS 6803:1999 Acoustics – construction noise(external link)

NZS 6803 is an independent standard produced by Standards New Zealand and provides guideline noise limits and management practices for construction and maintenance works. The noise limits apply outside neighbouring buildings, one metre from the building façade and 1.2 to 1.5 metres above the relevant floor level.

During the day, most people tolerate higher noise levels from temporary activities – such as construction -–compared to permanent activities. Therefore, noise limits for temporary works are higher during the day. However, at night the limits are much lower to prevent sleep disturbance, similar to those for permanent activities. Most construction work will be undertaken between 7.30am and 6:00pm Monday to Saturday, when noise limits are usually higher.

In New Zealand there is no standard or limit for construction vibration. As a result, projects typically adopt the vibration limits within the German Standard DIN 4150-3 and the British Standard BS 5228-2 to manage the effects of construction vibration. The British Standard includes consideration of effects on people, buildings, building contents and underground services. The German Standard primarily relates to effects on buildings.

DIN 4150-3:2016-12 Vibration in buildings – part 3: effects on structures(external link)  
BS 5228-2:2009+A1:2014 Code of practice for noise and vibration control on construction and open sites – vibration(external link)

As with noise limits, vibration limits that apply at night are usually much lower than during the day to manage sleep disturbance.

More detail on construction vibration limits can be found in the State highway construction and maintenance noise and vibration guide.

State highway construction and maintenance noise and vibration guide

There are times when noisier work outside of normal hours is unavoidable. For example, resealing a busy road may only be undertaken at night when the road or lanes can be closed to avoid significant traffic disruption. Neighbouring properties likely to be affected by noisy works will be notified, usually through a letter drop.

To manage construction vibration effects, the potential vibration levels of high-vibration activities will often be determined through measurements during a trial using the equipment at the site prior to works. Alternatively, calculations will be made in advance of the construction works and if necessary confirmed at the start of the works by measurements near to or at any at-risk locations.

Waka Kotahi does not routinely monitor vibration at individual properties to assess construction vibration, as the above measurement process is considered good practice to manage vibration. Occasionally monitoring may be undertaken to confirm vibration levels.

There is a wide range of sensitivity to vibration between different people. The threshold of human perception is a vibration magnitude in the region of 0.3 mm/s, but perception is also influenced by the duration of the vibration event, its frequency spectrum, when and how often the events occur, and whether the vibration is accompanied by noise. If items sitting on hard surfaces start to rattle, which can happen at vibration magnitudes as low as 1 mm/s, this can make us even more aware of the physical vibration. However, the vibration levels that would be required to cause building damage are much higher than this.

The vibration standards we use to manage construction vibration are conservative in their proposed limits to ensure vibration levels do not go above ‘safe’ vibration levels for the control of building cosmetic damage. Typically that limit is set at 5 mm/s, which is well below the onset of damage for most buildings, irrespective of their size, condition, or structural characteristics.

When building occupants can feel vibrations through the floor and hear windows rattling they may wonder whether building damage is occurring. It is quite common for existing cracks in walls that had previously gone unnoticed to then be attributed to construction works. In general, if there is a risk of vibration exceeding the ‘safe’ level at a property then before-and-after surveys of building condition will be conducted, which provide certainty around vibration effects on the building. For properties that are not expected to exceed the ‘safe’ level, the vibration can cause worry and concern, but very rarely any actual cosmetic effects, much less structural damage.

Vibration effects from high-vibration-generating activities such as piling, rock breaking and compaction do have the potential to exceed the ‘safe’ vibration levels if not appropriately assessed and managed. To ensure activities are appropriately managed, Waka Kotahi requires projects to implement a construction noise and vibration management plan (CNVMP). For further information go to our State highway construction and maintenance noise and vibration guide.

State highway construction and maintenance noise and vibration guide

Noise monitoring of construction works is generally undertaken on significant noise sources before or on commencement of activities likely to affect neighbours. This allows the project teams to understand if the noise is within the permitted noise limits and whether additional mitigation is needed.

Regular noise monitoring is also undertaken during noisy construction activities to confirm noise is within the permitted limits.

Waka Kotahi does not routinely monitor noise at individual properties to assess construction noise, as the above monitoring is considered good practice to manage noise.

The most effective method to control construction and maintenance noise and vibration is through proactive management. This includes assessment of all activities and consideration of potential noise and vibration effects and appropriate mitigation. 

To ensure this occurs for construction works that may have an adverse effect on neighbours, Waka Kotahi requires projects to implement a Construction Noise and Vibration Management Plan. This document details the obligations of Waka Kotahi and its contractors towards managing noise and vibration effects to avoid unreasonable effects on communities and individuals.

Some of the things we do and have done to reduce disturbance for neighbours are:

• keep neighbours informed of the construction activities that may affect them
• adopt quieter techniques and processes and select low-noise equipment where practicable
• build temporary noise walls on the site boundary to reduce the noise reaching nearby homes or put screens around noisy activities
• undertake regular noise monitoring to ensure any noise is within the permitted limits
• replace vehicle reversing beepers with ‘squawkers’ (broadband directional reversing alarms) at night
• prepare and implement activity specific schedules for night works and particularly noisy works that are predicted to be above the permitted noise limits to ensure mitigation and management measures are appropriately targeted to minimise disturbance as far as practicable
• all personnel involved in construction and maintenance noise management are required to have appropriate training
• brief the work teams on the behaviours expected of them, particularly on night works, to minimise unnecessary noise, for example shouting or slamming vehicle doors
• provide a clear process, such as a 24-hour freephone number, for neighbours to respond to complaints about unreasonable noise and vibration.

The State highway construction and maintenance noise and vibration guide contains further information on how we manage construction noise and vibration.

State highway construction and maintenance noise and vibration guide

Sounds you may hear include:

• tyre noise (or road-surface noise) – noise created as the tyre rolls along the road surface
• vehicle noise – engine/exhaust noise, rattling of vehicle bodies, noise of engine braking
• aerodynamic noise – noise created by turbulence around a vehicle as it passes through the air
• rumble strips – vehicles travelling over rumble strips can make a distinctive sound
• bridge joints – vehicles passing over them can make a distinctive percussive sound. 

At higher speeds (generally 50km/h and above) the dominant noise source from traffic is typically tyre or road-surface noise. At speeds lower than 50km/h, vehicle noise typically dominates. 

Traffic noise levels are influenced by a variety of factors, including: 

• traffic volume (the number of vehicles passing)
• traffic speed
• number of heavy vehicles/trucks
• driver behaviour
• road-surface type and condition
• noise barriers (eg bunds and walls)
• screening (anything blocking the sound path)
• reflections (sound bounced off hard surfaces)
• distance from the road
• the characteristics of the ground (including topology and ground surface cover)
• weather (wind/temperature inversion).

Exposure to high levels of environmental noise has been linked to cardiovascular disease, cognitive impairment in children, sleep disturbance, tinnitus and annoyance. Sleep disturbance and annoyance – mostly related to road traffic noise – constitute the bulk of these effects. 

Noise may also reduce enjoyment of outdoor areas such as gardens, decks and play areas. 

For more information read the World Health Organization Environmental noise guidelines for the European Region.

Environmental noise guidelines for the European Region(external link)

In New Zealand there are no national environmental or planning standards related to noise from existing roads. 

However, both the Health Act 1956 and the Resource Management Act 1991 empower local authorities (councils) to regulate noise that may be unreasonable or injurious to health, through district plan requirements and resource consent conditions. 

There are no numerical noise-level requirements or criteria in the Resource Management Act or the Health Act.

There are no national environmental or planning standards related to noise. However, there is a New Zealand standard – NZS 6806 – for the assessment of noise and noise mitigation for new and altered roads. New Zealand standards are not a legal requirement unless required by statutory approvals or incorporated by reference in regulations, statutes or district plans.

NZS 6806:2010 Acoustics – road traffic noise – new and altered roads(external link)

NZS 6806 sets out procedures and requirements for the prediction, measurement and assessment of road traffic noise for new and materially altered state highways and local roads. The standard also provides best-practice guidance and advice on methods for mitigating reverse sensitivity situations and the environmental effects of noise exposure on nearby noise-sensitive activities.

The standard considers health issues associated with noise, the effects of noise levels on people and communities, affordability considerations and the potential benefits of roads to people and communities. The standard recognises (as does the World Health Organization) ‘that the evaluation of control options must take account of technical, financial, social, health and environmental factors’.

The committee that developed the standard included representatives from a wide range of organisations such as Local Government New Zealand, Ministry of Health, Ministry of Transport, New Zealand Transport Agency, Road Controlling Authorities NZ, Department of Building and Housing, NZ Acoustical Society, NZ Institute of Environmental Health, Roading NZ and Ingenium.

NZS 6806 applies to both new and altered roads and may be a requirement of project statutory approvals (eg resource consent or designation conditions). NZS 6806 does not apply to existing roads. 

NZS 6806:2010 Acoustics – road traffic noise – new and altered roads(external link)

The definition of an ‘altered road’ under NZS 6806 is limited to changes in the road’s vertical or horizontal alignment that result in a significant change in average noise over the course of a day at nearby noise-sensitive receivers (such as a dwelling). The definition of an ‘altered road’ specifically excludes situations where only the road-surface, traffic speed, traffic volume, or traffic composition (that is the percentage of heavy vehicles) has changed.

NZS 6806 sets noise criteria for new and altered roads to achieve reasonable noise levels at residential dwellings and other noise sensitive activities. NZS 6806 is used to assess average traffic noise at residential dwellings close to the road (within 100m in urban areas and within 200m in rural areas) where noise effects are most likely to occur and to inform the best practicable option for noise mitigation.

NZS 6806:2010 Acoustics – road traffic noise – new and altered roads(external link)

Noise mitigation is not required to be considered for properties beyond 200m (rural areas) and beyond 100m (urban areas) under NZS 6806. This is because noise reduces with distance from the road, and also because there is often screening from the road at those distances by either the terrain or structures such as buildings, bridges, safety barriers and fences. In addition, noise barriers and/or low noise surfacing provided for houses closer to the road will also generally benefit those farther away.

Road traffic noise from existing state highways is managed through ongoing good practice road maintenance and improvement activities to provide a smooth surface. For example, repair of road defects (potholes, ruts, etc) and planned resurfacing.

There is currently no government funding for retrospective mitigation of noise from existing state highways, for example through installing noise barriers or low-noise surfacing. 

For more information about we manage noise in specific situations, see the ‘Engine braking’, ‘Loud vehicles’, ‘Reverse sensitivity’ and ‘Operational noise’ sections on this page.

Many people notice road-traffic noise after a new road is constructed or after an existing road is modified. In some cases, you might be more likely to notice road-traffic noise after road works or maintenance activities because your attention has been drawn to the road rather than there being an actual significant increase in noise. 

A common example of this is removal of roadside vegetation, where the road then becomes visible or partly visible. In most cases, removal of roadside vegetation will not cause a material increase in measured noise although it can increase perceived noise. 

When windows are open for ventilation this may increase indoor noise from outside sources. This may be particularly noticeable in spring and in summer after the windows have been shut for several months at night during the cooler autumn and winter seasons.

Other common sources of increases in road noise include: 

• if resurfacing work has been undertaken on the road there may be a change in noise levels or noise character because the surface type has been changed (for instance changing from an asphalt to a chipseal surface) or because the new surface takes some time to ‘bed in’
• traffic volume change or increase in the number of heavy vehicles such as for seasonal industries
• development of a fault in the surface, such as a pothole causing tyre ‘thumping’ noise or vehicle body noise (such as a rattle from a vehicle tailgate)
• meteorological factors, for example wind can cause noise to travel further from the road in the downwind direction.

Trees, shrubs and other vegetation generally provide minimal benefit in terms of reducing the actual noise levels. You may perceive an increase in noise with vegetation removal if the road then becomes visible and your attention is now being drawn to the road traffic, or individual vehicles become identifiable as a noise source. In most cases, removal of roadside vegetation will not cause a material increase in measured noise although it can increase perceived noise.

However, where roadside surface vegetation or grass is mostly or entirely replaced by a hard surface such as asphalt, or vice versa, it can make a difference to the actual road noise levels.

Increases in overall traffic volume or in the number of heavy vehicles will result in increased road-traffic noise. However, noise levels are not as sensitive to traffic volume as many people perceive. As a rule of thumb, a doubling of traffic volume will result in an increase of approximately +3 dB. 

As illustrated in the figure above, noise increases with vehicle speed. This figure also shows that at speeds above approximately 50km/h tyre noise becomes the dominant source of noise. At speeds less than 50km/h both vehicle (engine) noise and tyre noise contribute to the noise heard from the road.

Waka Kotahi does not typically monitor noise at individual properties in response to complaints or queries about road-traffic noise. 

This is primarily because specialised and long-duration monitoring (days to weeks) is required to measure road-traffic noise. And even then it can be difficult to reduce the influence of other environmental noise (such as wind and other weather, human activities, cicadas etc) and capture typical traffic conditions. This is also not a sustainable process across the more than 11,000km of state highways in New Zealand.

Even where noise monitoring may be practical and accurate, there are generally no standards or criteria for comparison of noise monitoring results. Therefore, the monitoring information only has limited use.

For road-traffic noise assessments for new roads and material alterations to existing roads noise models are used. Long-term monitoring is sometimes undertaken to verify the noise model, but noise measurements are not used to confirm compliance with project requirements at individual locations.

In general, smartphone apps are not a reliable way to measure noise because of the variability in hardware and the variable quality of apps.

Some smartphones and tablets can produce reasonably accurate noise measurements in still conditions, while others can be off by ± 10 dB or more. Unfortunately, without having a proper calibration performed, there is no way to know if the readings from a given device and app are reliable, even as a rough estimate.

Unlike sound level meters fitted with foam wind shields, mobile phones are very susceptible to wind noise, as well as the direction they are pointing. Another consideration is most noise criteria in New Zealand are averaged over time. While it may be practical to estimate construction noise over 15-minutes with a mobile phone, it is unlikely a mobile phone could be used to measure road-traffic noise over a 24-hour period.

As mobile phone noise measurements are not taken using an approved and calibrated device, as required by New Zealand noise standards, reliance cannot be placed on the readings.

Waka Kotahi does not typically monitor noise at individual properties to address complaints, concerns or compliance. 

This is particularly the case for houses located away from the road (greater than 50m to 100m from the road in urban areas and greater than 100m to 200m from the road in rural areas). 

This is because in these locations, noise from the road may not be ‘dominant’. Dominant means noise levels are significantly above background (residual sound) levels. Background noise levels also include noise from wind and other weather, insects, human activities (such as talking, lawn mowing, use of a car, heat pump etc) or noise from local roads. 

In locations where the road noise is not dominant, it does not mean you will not be able to hear noise from the road. In fact, you might be able to hear noise from the road clearly – especially at night.

Noise monitoring measures the total noise at a location from all sources. When noise from background/ambient noise sources is dominant or similar to noise from the road it can be difficult to attribute noise to a specific source. 

For example, if the background (residential sound level) noise level is 40 dB and the noise level from the road is 55 dB then the total noise level is 55.1 dB (the logarithmic sum of 40 dB and 55 dB). In this example, the road noise is dominant because the background noise has only a small influence on the total noise level and it is relatively easy to attribute the noise level to the road. 

As the ‘road’ and ‘background’ noise levels get closer to each other, the influence of the background noise level on total noise level (background plus road) in decibels is greater. For example, if both the background and road noise levels are 40 dB the total noise level is 43 dB (the logarithmic sum of 40 dB and 40 dB). In this example, it is more difficult and unreliable to differentiate the contribution of noise from the road and from background.

Waka Kotahi has a map of noise exposure across the state highway network.

This map shows areas of potential ‘high’ noise exposure based on noise modelling, using information such as traffic data, road surfacing, location of building (house) footprints and ground level in relation to the road.

Across the state highway network, terrain and house location information is available in inconsistent detail. This means the map is not sufficiently accurate to reliably predict noise exposure at all individual houses but is sufficient to identify broader areas of potential high noise exposure.

Due to potential privacy concerns and the limitations of the map, we do not share information about noise exposure at individual properties or houses.

At present there is no government funding available to provide noise barriers or low-noise surfaces along the existing state highway network.  

For new roads and material alterations to existing roads Waka Kotahi will assess noise exposure at existing dwellings and provide noise mitigation as required to meet the designation requirements.

Changes to the posted speed limits must follow Land Transport Rule: Setting of Speed Limits 2022. The rule is primarily focused on the safety and efficiency of road networks. It does not consider the relationship between traffic speed and noise, and thus does not provide a route to noise mitigation.

In urban areas, traffic calming measures can be more effective than simply altering speed limits. This is particularly so in residential areas. Typical traffic calming measures may include road narrowing, traffic islands, pavement changes and speed humps.

In New Zealand, the term ‘noise barrier’ includes solid walls, fences, and bunds (banks of earth). Usually it refers to structures specifically intended to provide noise screening as part of their main purpose.

Sound (noise) travels in waves but may be thought of as travelling as a ray. Sound waves can be absorbed, reflected or diffracted (bent) by noise barriers. Absorption, reflection and diffraction all reduce the energy of sound and thus the noise level, which is commonly measured in decibels.

Sound paths with a noise barrier in place (on level ground)

Without a noise barrier in place, the straight sound path is usually the most significant. By introducing a barrier between the source and the receiver (such as a dwelling), the amount of sound reaching the receiver can be reduced. While reflected noise, diffracted noise, and transmitted noise may still reach the receiver – as noted above – the overall noise levels will be reduced. 

To provide the most noise reduction barriers should block line of sight from all parts of a dwelling to all points of a road and to all vehicles using the road. 

We have prepared a guide for noise barriers, which is available on our website. The intended audience for this guide is primarily engineers, architects and contractors, but may be of general interest to homeowners and developers.

State highway noise barrier design guide

The best location for a noise barrier depends on the position of the receiver in relation to the road. 

Barriers should ideally block line of sight from all rooms of a receiving building to the surface of the adjacent section of road. In practice this may require a very tall and/or very long barrier that could be impractical to construct.

Noise barrier length

Noise barrier with return

In general, the best location for a noise barrier is as close to the road as possible when houses are located below the road. 

Level ground with noise barrier

When houses are located at the same level or above the road the most effective barrier location may be as close as practical to the house.

Noise barrier located at top of cutting

Care needs to be taken during the design and location of barriers to consider urban design effects and on-going maintenance requirements, in addition to district plan requirements. Other effects of barriers that should be considered include shading, visual effects, access, safety and surface/storm water flow. 

Waka Kotahi does not provide noise barriers on privately owned land to reduce noise from existing roads. 

We have prepared a guide for noise barriers, which is available on our website. This guide provides more details on the factors that influence noise barrier details and siting.

State highway noise barrier design guide

Waka Kotahi does not provide building or property noise treatments for houses exposed to noise from existing roads.

We have prepared a guide on building and property noise treatments, which is available on our website. The intended audience for this guide is primarily engineers, architects and contractors, but may be of interest to homeowners and developers.

State highway guide to acoustic treatment of buildings

Waka Kotahi does not compensate property owners for actual or perceived loss of value of their property related to traffic noise from existing roads.

Supplementary braking systems are provided on heavy vehicles to assist the normal ‘service brakes’ in maintaining safe speeds travelling down hills. There are three main types of supplementary braking systems:

• exhaust brakes: a device intermittently blocking the exhaust to create back pressure on the engine
• engine brakes: a device releasing compressed gases from the engine
• retarders: electric or hydrodynamic devices installed in the driveline.

Engine brakes are typically used on large trucks, whereas exhaust brakes are common on medium trucks. 

Modern engine and exhaust brakes include silencers and are unlikely to cause significant noise disturbance.  

Some older heavy vehicles have unsilenced or ineffectively silenced engine brakes which produce loud noise and may cause noise disturbance.

Further details can be found in our leaflet about engine braking noise.

Engine braking noise leaflet [PDF, 331 KB]

Engine and exhaust brakes give rise to a series of noise pulses, which can have a distinctive sound – often described as a ‘machine gun’ or ‘barking’ noise. 

Other vehicle noise such as normal heavy vehicle acceleration and deceleration can produce noise commonly confused with engine braking, as can the sound of vehicles travelling on rumble strips. Monitoring has shown the occurrence of ineffectively silenced engine braking is quite low, even in areas of significant reported disturbance.  

Waka Kotahi has completed long-term monitoring of engine braking at several locations across the state highway network. This monitoring indicates the frequency of engine braking is generally quite low – often less than one event per day – even in areas where residents report frequent disturbance from engine braking.  

This monitoring has shown loud noise from engine braking is not as frequent as loud noise from other vehicles, such as motorcycles, modified cars, sirens or other heavy vehicle noise – such as acceleration or deceleration noise without engine brakes.  

Other vehicle noise such as routine heavy vehicle acceleration and deceleration can produce noise which is commonly confused with engine braking, as can the sound of vehicles travelling on rumble strips.

Waka Kotahi has limited ability to influence the use of engine brakes on the road. The primary tools are liaison with trucking operators and industry groups to influence driver behaviour and also liaison with the NZ Police to identify areas for potential enforcement of excessive noise rules. Waka Kotahi does not have an enforcement role for on-road use of engine brakes.

We can undertake engine braking monitoring to identify the scale of the potential engine braking problem in the area and identify individual vehicles that are using engine brakes. This information is not used for enforcement but rather to assist and focus liaison with the trucking industry and the NZ Police. 

In some circumstances Waka Kotahi can provide signs either advising no engine braking or prohibiting engine braking. An engine braking prohibition requires consultation and enactment of a bylaw and can only be implemented if the posted speed limit on the road is 70 km/h or less.  More information can be found about engine braking prohibitions in the Land Transport (Road Safety and Other Matters) Amendment Act 2011.

Land Transport (Road Safety and Other Matters) Amendment Act 2011(external link)

Additional information on how we manage noise disturbances from trucks engine braking on state highways can be found in our technical memorandum on engine breaking noise.

Technical memorandum: Noise and vibration no.6 – Engine braking noise (2014) [PDF, 75 KB]

Waka Kotahi has two special noise monitoring devices with cameras to record engine braking events and the details of the vehicles using engine braking. The decision to install a noise camera is based on the following: 

• likelihood engine braking would occur in an area
• number of houses nearby the road that might be disturbed by engine braking
• availability of a suitable location to install the noise camera
• community documentation of engine braking (date, time and location of observed engine braking)
• extent of the actual adverse effect occurring
• availability of funding to install and manage the monitoring equipment.

There is typically a waiting time of one to two years from the time a location is identified to install the noise camera and the actual installation. This is because the two cameras are prioritised across the entire state highway network and there is generally a waiting list. 

The information generated from the noise camera is used for liaison with the trucking industry and individual drivers to advise of the disturbance caused by engine braking, and to influence behaviour to reduce engine braking in built up areas where it is most likely to cause disturbance. 

This information may also be shared with the NZ Police to help them focus enforcement of excessive noise rules. However, the monitoring cameras themselves are not used directly for enforcement.

Further details can be found in our leaflet about engine braking noise.

Engine braking noise leaflet [PDF, 331 KB] 

If you are experiencing regular or routine disturbance by engine braking noise, documentation of this information can assist Waka Kotahi to liaise with organisations that might be able to influence driver behaviour.  

Keep a log of date and times when you observe engine braking over a period of two weeks (ideally longer). In most instances it is not practical to identify individual heavy vehicles that are potentially engine braking but if you can document information identifying the vehicle (such as company name) this can be helpful with liaison efforts. 

This information may be used by Waka Kotahi for liaison with the trucking industry to advise of the disturbance caused by engine braking, and to influence behaviour to reduce engine braking in built up areas where it is most likely to cause disturbance. This information may also be shared with the NZ Police to highlight community concerns and help them focus enforcement of excessive noise rules, if appropriate.

In some circumstances, Waka Kotahi can provide signs either advising no engine braking or prohibiting engine braking. 

Several factors are considered prior to installing ‘No engine braking’ signs. These include the following: 

• safety implications of limiting engine braking on the road
• likely effectiveness of signs in reducing engine braking
• likelihood that engine braking would occur in an area
•  number of houses nearby the road that might be disturbed by engine braking
• community documentation of engine braking (date, time and location of observed engine braking)
• number of people reporting disturbance from engine braking in the affected area.

An engine braking prohibition requires consultation and enactment of a bylaw and can only be implemented if the posted speed limit on the road is 70km/h or less. This is because engine brakes are important supplementary safety device for slowing vehicles down in some situations, for example on higher speed roads or on steep declines.  

More information can be found about engine braking prohibitions in the Land Transport (Road Safety and Other Matters) Amendment Act 2011.

Land Transport (Road Safety and Other Matters) Amendment Act 2011(external link)

No specific studies have been completed to assess the effectiveness of ‘No engine braking’ signs. It is considered such signs are likely to have limited effectiveness but would most likely be beneficial in areas where drivers might not realise there are nearby dwellings that may be disturbed by engine braking. Waka Kotahi still receives reported disturbance from engine braking noise in areas where signs have been erected.  

Overuse of signs, including ‘No engine braking’ signs, can cause visual clutter or habituation, meaning the messages that signs convey may not be readily noticed or actioned by drivers. As a result, installation of signs should be carefully assessed to make sure they are likely to be effective in reducing noise disturbance caused by engine braking.

NZ Police are responsible for enforcing the Land Transport (Road User) Rule 2004 for excessive noise for on road vehicles. This includes engine braking noise deemed to be excessive. The enforcement of the excessive noise rule for engine braking may occur regardless of whether there are ‘No engine braking’ advisory or prohibitory signs.

Land Transport (Road User) Rule 2004(external link)

The Land Transport (Road User) Rule includes the following provision (rule 7.4) for on road vehicle noise:

A driver must not operate a vehicle that creates noise that, having regard to all the circumstances, is excessive.

…

In determining whether any noise is excessive, regard may be had, in addition to all other relevant matters, to—

(a)  the manner of operation of the vehicle:

(b)  the condition of the vehicle:

(c)  the time of the day when the noise is created:

(d)  the locality where the noise is created:

(e)  the likelihood of annoyance to any person:

(f)  any relevant standard or specification that applies under the Act.

Where there is a bylaw prohibiting engine braking a fine can be specified. The specific provisions contained in any bylaw will determine who might enforce it. If the bylaw is simply a ban on the use of engine brakes by heavy motor vehicles it would normally only be enforceable by NZ Police.

Section 2.7 of the Land Transport Vehicle Equipment Rule 2004 sets out noise requirements for vehicles entering service (vehicles being imported and/or registered in New Zealand for the first time).  In summary, this rule requires most vehicles entering service be manufactured to a standard complying with the noise levels. If the vehicle has been modified to increase the noise output from the original (complying) exhaust system, then individual testing of the vehicle may be required to demonstrate that the maximum noise levels are not exceeded before it can enter service.

Land Transport Vehicle Equipment Rule 2004

For in-service vehicles (that is vehicles already registered in New Zealand) the Land Transport (Vehicle Equipment) Rule requirement is they not ‘be noticeably and significantly louder than the noise output from the vehicle’s original exhaust system at the time of the vehicle’s manufacture’. This may be confirmed during the certificate of fitness (CoF) inspection process for heavy vehicles. There are no in-service maximum noise levels for heavy vehicles.

Waka Kotahi has limited ability to control noise from individual vehicles on the road. Where heavy vehicles are the cause of the noise we can liaise with trucking industry groups to influence driver behaviour. 

We can also liaise with the NZ Police to identify areas for potential enforcement of excessive noise rules.

The warrant of fitness (WoF) and certificate of fitness (CoF) processes both allow for checks to confirm that individual vehicles meet applicable noise regulations and requirements.

If you are experiencing regular or routine disturbance by loud noise from individual vehicles, documentation of the occurrences can assist Waka Kotahi liaise with organisations that might be able to influence driver behaviour – such as industry groups and the NZ Police.  

Keep a log of date and times when you observe the loud noise over a period of two weeks (ideally longer). In most instances it is not practical to identify individual vehicles (eg by the licence plate) but if you can document information identifying the vehicle (such as company name) this can be helpful with liaison efforts. 

This information may be used by Waka Kotahi for liaison with the trucking industry (where noise from heavy vehicles is of concern) to influence behaviours which might be causing disturbance. 

This information may also be shared with the NZ Police to highlight community concerns and help them focus enforcement of excessive noise rules (if appropriate).

Section 2.7 of the Land Transport Vehicle Equipment Rule 2004 sets out noise requirements for vehicles entering service (vehicles being imported and/or registered in New Zealand for the first time). In summary, this rule requires most vehicles entering service be manufactured to a standard complying with the maximum noise levels. If the vehicle has been modified to increase the noise output from the original (complying) exhaust system, then individual testing of the vehicle may be required before it can enter service to demonstrate that the maximum noise levels are not exceeded.

Land Transport Vehicle Equipment Rule 2004

For in-service vehicles (vehicles already registered in New Zealand) the Vehicle Equipment Rule requires most light/mid-weight vehicles (motorcycles, cars, vans and light goods vehicles) comply with maximum noise levels. This is sometimes confirmed during the warrant of fitness (WoF) inspection, where the vehicle inspector may perform a subjective check on vehicle noise.

This subjective check does not include noise measurements but relies upon the inspector’s judgement as to whether the vehicle may exceed the maximum noise levels. If the vehicle fails the WoF check because of a noisy exhaust, the inspector may refer it for an objective noise test. In the objective noise test, the noise levels are measured with a calibrated noise meter and the results compared against the maximum noise levels included in the rule. Vehicles not meeting these requirements may require repair or replacement of noisy exhaust systems before returning to on-road use.

More on the objective noise test can be found on our website.

Noise tests for exhausts

The Vehicle Equipment Rule requirement for heavy vehicles is different from light and mid-weight vehicles. The requirement is that in-service vehicles must not ‘be noticeably and significantly louder than the noise output from the vehicle’s original exhaust system at the time of the vehicle’s manufacture.’ This may be confirmed during the certificate of fitness (CoF) process.

The NZ Police are responsible for enforcing the Land Transport (Road User) Rule 2004 for excessive noise for on road vehicles.

Land Transport (Road User) Rule 2004(external link)

The Land Transport (Road User) Rule includes the following provision (rule 7.4) for on road vehicle noise:

A driver must not operate a vehicle that creates noise that, having regard to all the circumstances, is excessive.

…

In determining whether any noise is excessive, regard may be had, in addition to all other relevant matters, to—

(a)  the manner of operation of the vehicle:

(b)  the condition of the vehicle:

(c)  the time of the day when the noise is created:

(d)  the locality where the noise is created:

(e)  the likelihood of annoyance to any person:

(f)  any relevant standard or specification that applies under the Act.

For light and mid-weight vehicles (most cars, vans, motorcycles and light goods vehicles) the police may require that vehicle undergo an ‘objective noise test’ before being used on the road again. In the objective noise test, the noise levels are measured with a calibrated noise meter and the results compared against the maximum noise level limits. Vehicles not meeting these requirements may require repair or replacement of noisy exhaust systems before returning to on-road use.

More on the objective noise test can be found on our website.

Noise tests for exhausts

By law, the noise coming from a vehicle’s exhaust system must be similar to or less than the noise it made when the vehicle was manufactured. Two exceptions are where:

• the noise the exhaust emits is still well below legal noise limits
• an ‘objective noise test’ proves the noise doesn’t exceed the legal noise limits.

During a warrant of fitness (WoF) inspection, the vehicle inspector may perform a subjective check on vehicle noise. This check does not include noise measurements but relies upon the inspector’s judgement as to whether the vehicle may exceed the maximum noise level limits. 

If the vehicle fails the WoF check because of a noisy exhaust, the inspector may refer it for an objective noise test. In the objective noise test, the noise levels are measured with a calibrated instrument and the results compared against the maximum noise level limits. Vehicles not meeting these requirements may require repair or replacement of noisy exhaust systems before returning to on-road use.

More on the objective noise test can be found on our website.

Noise tests for exhausts

For heavy vehicles the requirement is they must not be noticeably and significantly louder than the noise output from the vehicle’s original exhaust system at the time of the vehicle’s manufacture. This may be confirmed during the certificate of fitness (CoF) process.

Unfortunately, there is unavoidable noise and other effects associated with highway use, operation, maintenance and construction.

Exposure to environmental road-traffic noise has been linked to ischemic heart disease, hypertension, sleep disturbance and annoyance.

As well as contributing to some of these adverse effects, noise outdoors may also reduce general enjoyment of areas such as gardens, decks and play areas.

Tension can therefore arise between the need to operate and maintain a safe and efficient highway network and the desire for neighbouring property to be free from interference or nuisance.

While Waka Kotahi takes care to manage unreasonable nuisance or interference, disturbance at sensitive receivers, for example houses, schools and marae, can still arise. Careful planning by managing establishment of new activities creates social benefits in that it provides sensitive receivers with greater health and wellbeing, while still allowing the efficient movement of people and goods between communities.

A noise-sensitive activity can be:

• any residential activity (including visitor accommodation and retirement accommodation)
• any educational activity
• any healthcare activity
• any congregations within places of worship or marae.

Managing reverse sensitivity effects requires a shared approach. This is because it is neither practical nor reasonable for landowners, developers, councils or Waka Kotahi to assume sole responsibility.

When landowners or developers establish a new dwelling (or other noise sensitive activity) or alter an existing dwelling next to the state highway (or a planned or designated road) they have a duty to mitigate the effects of their activity on the state highway. That is, they should ensure noise and vibration arising from a nearby road do not cause unreasonable disturbance to occupants of a dwelling – in particular, sleep disturbance.

Councils have a duty to establish appropriate land use zoning, planning and consenting controls/requirements, primarily through district plans, to make sure that the effects of noise-sensitive activities on established or designated roads are managed. Careful and considered planning is pivotal to both protecting the environment and enhancing the quality of life for New Zealanders.

Waka Kotahi is responsible for implementing good practice maintenance on existing roading infrastructure to manage noise and vibration arising from the road. For new roads or significant alterations to existing roads, Waka Kotahi is also responsible for ensuring noise exposure and vibration impacts on existing nearby sensitive land use (such as an existing dwelling) is reasonable.

Separation is often the most effective method of mitigating effects such as noise, vibration, vehicle emissions, lighting/glare and dust on people in houses. In general, the greater separation distances will result in reduced noise, vibration and other impacts, and improve outdoor amenity, such as the use of decks and gardens.

While separation of new houses can be beneficial to avoid or reduce highway noise and vibration effects, Waka Kotahi recognises that in some areas other constraints dictate that sensitive activities should be allowed closer to highways, even though there is an undesirable noise environment. In these instances, there may be greater cost constructing a building that adequately reduces higher external noise and vibration levels to achieve healthy conditions inside.

Each house (or other noise sensitive activity) in the area identified around a state highway will require an assessment to confirm the acoustic treatment required to meet the recommended internal noise and vibration levels.

This is because site specific characteristics such as the terrain, location and orientation of the dwelling (or sensitive activity), traffic characteristics and road characteristics all influence noise exposure and vibration. The cost to acoustically treat a house will therefore vary from situation to situation.

Waka Kotahi does not provide advice related to compliance with the internal noise and vibration level requirements. We recommend you engage the services of a suitably qualified acoustics professional and a building design professional.

The most common form of acoustic treatment is the provision of ventilation and cooling systems, which allow windows to remain closed to reduce interior noise levels.

We have developed tools (calculators) and guidance for building and property noise treatments. The intended audience for these is primarily engineers, architects and contractors, but may be of general interest to homeowners and developers.

The road traffic noise calculator provides a prediction of exterior noise exposure at dwellings where the terrain, building and road are not complex.

Road traffic noise calculator

The internal noise calculator allows the internal noise level to be estimated based on the building construction and a specified external noise level (from the road-traffic noise calculator). Noise is predicted through the wall facing the road, and optionally through the roof, windows and doors. Both the total noise level and the path contributions are displayed.

Internal noise calculator

We have also prepared a guide on building and property noise treatments.

State highway guide to acoustic treatment of buildings

Separation and screening of a dwelling or sensitive activity from the road are the two best ways to comply with noise and vibration requirements. This is because these methods improve outdoor noise amenity, for example for the use of gardens and deck, while also reducing or eliminating the requirement for building acoustic and/or vibration treatments.

Orientating and siting a building so living areas and especially bedrooms, are facing away from the road and/or are screened by terrain or other solid barriers will improve indoor noise levels. It can also be beneficial if primary outdoor amenity areas such as decks, gardens and play areas are screened from the road by the dwelling, terrain and/or other solid barriers.

In some instances, barriers such as walls, fences (with no gaps between palings) or earth bunds, may be all that is needed to comply with the internal noise level requirements. An effective barrier provides the benefit of not only reducing indoor noise levels but also outdoor noise levels, improving outdoor amenity.

Care needs to be taken during the design and location of barriers to consider urban design effects and maintenance requirements. To be effective, noise barriers for individual developments or dwellings need to join up with other noise barriers or extend wider than the area to be protected and should block line of sight from all parts of the dwelling to all parts of the road. Otherwise it may be necessary for the barrier to include return sections at each end of the barrier perpendicular to the highway.

We have prepared a guide for noise barriers which is available on our website. The intended audience for this guide is primarily engineers, architects and contractors but may be of general interest to homeowners and developers.

State highway noise barrier design guide

Waka Kotahi does not allow the construction of barriers (solid walls, fences or bunds – a bank of earth) within the road reserve to benefit new or altered noise sensitive activities. This is because such barriers may cause ongoing maintenance costs, access and safety issues.

Yes, closing windows can significantly reduce the road-traffic noise heard inside a building. In many situations, this is the only measure required to achieve the required internal noise levels.

However, closing windows may compromise the natural ventilation and cooling of a building. Where windows need to be closed to achieve reasonable internal sound levels, mechanical ventilation and in some cases, cooling will be required.

Care should be taken when choosing mechanical ventilation to avoid systems that are excessively noisy. Supplemental cooling may be required in some parts of the country that are hot in summer months.

No, Waka Kotahi does not accept encumbrances or other legal protections instead of compliance with indoor noise and vibration requirements.

No, trees or shrubs generally provide minimal benefit in terms of reducing actual noise levels. However, there is usually a perceived reduction in noise when a road is visually screened by trees or shrubs, which can have benefits.

Trees and shrubs are a practical method for visually screening the road, noise walls or bunds (banks of earth) and reducing graffiti.

It is likely road-traffic noise will be noticeable even at distances greater than 100m from a road.

For further information, see our guide.

Guide to the management of effects on noise sensitive land use near to the state highway network

The primary impact of road-traffic vibration is perceiving or ‘feeling’ vibration. There is a wide range of sensitivity to vibration, with some people able to feel low levels of vibration.

People can generally feel very low levels of vibration when they are focused – especially when they are resting or completing an activity that is quiet and/or requires concentration. This is particularly true when there is noise associated with a vibration event, such as the noise of a heavy vehicle passing by coincident with vibration.

In some cases vibration might be annoying – especially at night when it is generally quieter inside and outside of a house, and both noise and vibration are more noticeable. This annoyance can occasionally lead to sleep disruption or concerns about damage to your house or property.

Although some people become concerned, it is unlikely road-traffic vibration levels will be high enough to cause cracks or other structural or aesthetic damage to a building.

Waka Kotahi does not routinely undertake vibration monitoring in response to customer complaints and queries. If you are concerned about vibration at your house, we will undertake the following process:

• review the location of your house with respect to the road
• review records of road surface condition near your house
• potentially conduct a site visit to review the current road-surface condition and to observe felt vibration when heavy vehicles pass by.

Problematic vibration can arise from a defect in the road surface such as potholes, rutting or a poor transition to a manhole cover. Vibration monitoring is not required to identify these defects, as they will be visible to the person reviewing the query/complaint.

For new roads and most existing roads, it is unlikely road-traffic vibration will exceed established criteria for predicting annoyance or damage.

Generally, when significant new vibration can be felt inside a house this is a result of a nearby road-surface defect such as a pothole, rutting, or a manhole with an abrupt transition to the surrounding road surface.

If such a defect is confirmed, Waka Kotahi will review the significance of the vibration concern, the condition of the road, and any programmed road maintenance/re-surfacing work in the area and develop a plan to repair/correct the defect, if required.

In some cases, there may be issues with the road pavement (the engineered ‘soil’ layer that provides a strong and stable base for a smooth road surface) which can cause vibration to travel farther from the road and/or be more noticeable. In such cases Waka Kotahi will review the requirement to re-construct the road pavement. This is a major undertaking and, if required, would likely be programmed in at the time of the next major road rehabilitation/resurfacing work in the area.

People can feel vibration at approximately 1/20th of the level where minor building damage may occur. It is unlikely road-traffic vibration would cause cracks or other structural or aesthetic damage to buildings. Typically cracks and other similar damage result from building construction defects, natural building ageing effects or ground movement (beneath foundations), such as that resulting from clay shrinkage or building settlement.

However, people can notice existing damage such as cracks in a wall or ceiling lining if they notice vibration from a road or other sources. This is because feeling vibration can raise concern of damage and can draw attention to existing damage that was previously unnoticed or forgotten.

Concerns about vibration can be heightened by noise, for instance the noise of a loud truck passing by may cause your windows to rattle or ground vibration might cause glasses in a cabinet to rattle. This noise may make vibration levels seem greater than they actually are. This is particularly true at night, when it is generally quieter inside and outside a house, and both noise and vibration are more noticeable.

There are several factors that influence vibration arising from road traffic at nearby houses. These include the following:

• Distance from road to house: Vibration magnitude decreases with distance from the road. Although it is uncommon, vibration may occasionally exceed predicted annoyance criteria [RJ1] when a house is located within 20m of the active carriageway of a road. At distances greater than 20m it becomes increasingly less likely that annoyance criteria will be exceeded.
• Condition of road surface: In most cases where significant vibration is identified, the cause is a defect in the road surface, such as a pothole, rutting, or a poor transition to a manhole cover or between sections of road surface.
• Traffic conditions: Road traffic vibration is related to traffic volume (number of vehicles travelling a road per day will affect frequency of occurrence), traffic speed (vibration magnitude is proportional to speed), and the number of heavy vehicles using a road. 
• Presence of underground services/utilities: In some cases vibration might travel farther from a road or occur at higher levels if underground services are poorly constructed (generally poor backfilling of a trench), and/or if services such as waterlines or drains are leaking causing deterioration of trench backfill.
• Ground conditions: The magnitude of vibration and the distance vibration levels are felt can depend on the both the soil type and the stratification of soil. Vibration travels farther in hard/stiff soils than in loose/soft soils. Vibration can also travel ‘preferentially’ in hard/stiff layers of soil. 
• House construction and condition: The type and condition of house foundations can influence vibration levels felt inside. Vibration is more likely to be felt in houses with foundations in poor condition, foundations with ‘rigid’ connections between the ground and the house, and/or with significant surface area contact between the ground and the foundation. House construction can also influence the vibration levels felt inside, such as whether there is a timber or concrete floor. Upper floors are sometimes more sensitive to vibration than the ground floor.
• Road pavement condition: In some cases, road pavements (the engineered soil layer provided beneath the road surface to allow for a stable and smooth road surface) deteriorate over time causing defects in the road surface that might cause vibration issues. Occasionally, pavements in poor condition may also directly induce vibration in near surface soils that can be felt at nearby houses.
• Presence of road safety treatments: Vehicles traversing raised safety platforms and speed bumps can be a source of vibration. Heavy vehicles exceeding the design speed of the treatment pose the most risk of generating noticeable vibration.

Rattling of building components, such as windows, is most commonly caused by wind or the pressure from sound waves travelling through the air rather than from ground vibration (vibration travelling from the road through the ground to the building foundation). 

However, ground vibration may occasionally cause windows to rattle, notably where there are defects (such as potholes or rutting) and other surface features such as manholes or road surface joints.

Given the sound waves and ground vibration might occur at the same time it can be difficult for people to distinguish the cause of window rattling.

When traffic vibration occurs at night it may seem to be worse/stronger, but it is likely just more noticeable in the absence of other sources of household vibration. When we are trying to relax or sleep, we are often more sensitive to vibration, so vibration may cause more potential disturbance than it would during the day.

In some circumstances trucks may be travelling at higher speeds at night (eg in rural towns), which may lead to an actual increase in vibration.

Concerns about vibration can be heightened by noise, for instance the noise of a loud truck passing by may cause windows to rattle, or ground vibration might cause glasses in a cabinet to rattle. Noticing noise may make vibration levels seem greater than they actually are. This is particularly true at night, when it is generally quieter inside and outside a house, and both noise and vibration are more noticeable.

There are no New Zealand standards applicable to annoyance or damage from road traffic vibration. In the absence of a New Zealand Standard, Waka Kotahi has adopted Norwegian Standard NS 8176:2017 Vibration and shock – measurement of vibration in buildings from land-based transport and guidance to evaluation of its effects on human beings. 

NS 8176:2017 Vibration and shock – measurement of vibration in buildings from land-based transport, vibration classification and guidance to evaluation of effects on human beings(external link)

NS 8176 sets out vibration levels for roads based on human response (perception and annoyance) to vibration. Waka Kotahi applies this standard to ‘vibration sensitive’ activities, such as interior residential and educational activities, hospitals and places of worship. These criteria are not applied to commercial or industrial activities or businesses. 

For new roads, and also for significant alterations to existing roads (such as a road re-alignment bringing traffic lanes closer to a house), Waka Kotahi will endeavour to meet the Class C vibration criteria in NS 8176, where practicable.

For existing roads, Waka Kotahi will investigate and, if appropriate and practicable, seek to mitigate road-traffic vibration in dwellings found to exceed Class D in NS 8176.

Meeting either Class C or Class D criteria does not mean vibration will not be felt or that vibration will not cause disturbance or annoyance. These criteria are based on community response to vibration, acknowledging that while most people will find these vibration levels reasonable, a portion of the population may be annoyed/disturbed.

Waka Kotahi has also adopted the applicable criteria from both British standard BS 7385-2:1993 Evaluation and measurement for vibration in buildings – guide to damage levels from groundborne vibration and DIN 4150-3:2016-12 Vibration in buildings – part 3: effects on structures. These international standards relate to building damage from vibration (as distinct from NS 8176, which relates to annoyance/disturbance to people). 

BS 7385-2:1993 Evaluation and measurement for vibration in buildings – guide to damage levels from groundborne vibration(external link)
DIN 4150-3:2016-12 Vibration in buildings – part 3: effects on structures(external link)

The damage criteria in BS 7385-2: 1993 and DIN 4150-3: 2016-12 are significantly higher than those in NS 8176, and seldom come in to play when assessing road-traffic vibration.

Further information on vibration effects and management can be found in our Guide to state highway road surface noise and technical memorandum on state highway noise and vibration management.

Guide to state highway road surface noise
Technical memorandum: Noise and vibration no.3 – State highway noise and vibration management (2013) [PDF, 68 KB]