Road traffic vibration Road traffic vibration

Road traffic vibrations are typically perceived or felt due to heavy vehicles such as buses and large trucks that travel over irregularities in the road surface. This can be common on high volume roads such as arterials or collector roads.

Factors causing road traffic vibrations

The causes of vibrations from road traffic are complex and can depend on numerous factors such as:

road surface imperfections
driving speed
vehicle weight
weak soils
house foundation/construction type, or its condition.

We’ve investigated these types of concerns with acoustic (noise and vibration) consultants. Their advice is that while road-traffic vibration might cause concern or disturbance, the vibration levels seldom reach levels which would cause damage to buildings or structures.

You can also find answers to frequently asked questions about noise and vibration on the Waka Kotahi website.

The following information is more relevant to the local road network.

Factors that influence road-traffic vibration levels at your house

There are several factors which influence the road traffic vibration felt within a house.

Distance between the house and the road: Road traffic vibration levels generally decrease with distance from the road.
Road surface condition: In some instances, an uneven road surface with a defect such as a pothole, rutting, or non-level transitions to utility lids in the road can be the cause of a vibration sensation.
Traffic conditions: Road traffic vibration is related to
- the number of vehicles travelling a road per day (which affects how often vibration can be felt)
- the speed of traffic (higher speeds means higher vibration levels), and
- the number of heavy vehicles using a road such as trucks and buses.
Ground or soil conditions: The magnitude of vibration and the distance vibration levels are felt can depend on both the soil type and the layers of specific soil types. Vibration travels farther in hard/stiff soils than in loose/soft soils.
House foundation/construction type and condition: Vibrations are more likely to be felt in houses with foundations in poor condition, house foundations with ‘rigid’ connections between the ground and the house, and/or houses where the contact between the ground and the foundation makes up a large surface area.
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.
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.

Perception of vibration from a source and the effect on property. The higher the vibration, the more likely it is to impact you.

Damage caused by road traffic vibrations

People can feel vibration at levels approximately ten times lower than the level where minor building damage may occur. It is highly 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 about property damage and draw attention to existing damage that was previously unnoticed.

Noticing vibrations at night

In most cases normal daily household activities (such as walking in a house, cleaning, cooking, etc.) cause vibration levels greater than that from road traffic. These types of activities are less common at night and thus background vibration levels are generally lower. As a result, when vibration occurs at night, it may seem to be worse, but it is likely just more noticeable in the absence of other sources of vibration.

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. 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.

If you think vibrations damaged your property

If you are concerned about damage to your property, please contact your insurance provider.

Alternatively, we request that evidence is provided to Auckland Transport showing a clear link between the road traffic vibration and the property damage. This evidence may be in the form of an assessment from an independent consultant, who has assessed your property. We generally request that residents provide this evidence to ensure that results are independently verified by suitably qualified experts.

Our complaint handling process

Our process for road traffic vibration complaints usually begins with a site visit, where we check:

Road surface: If the uneven road surface is a potential contributing factor to road traffic vibration, then remedial works will be planned, noting that most of the network’s road surface, is maintained to a level that is safe and efficient for road users.
Existing infrastructure: Where there are existing speed-calming devices the construction is checked against specifications to ensure that they meet the correct standards. If there are any issues identified, we will work to resolve these.
Driver speeds: For most roads in Auckland, drivers are travelling at safe and appropriate speeds. However, if there is existing speed calming infrastructure which is not having the appropriate impact on driver speeds, we consider whether signage or road markings could support lower driver speeds on a given road.

Vibration monitoring is not routinely undertaken

Auckland Transport does not routinely undertake vibration monitoring at properties in response to customer complaints and queries.

We have undertaken a number of surveys and investigation across the Auckland in order to assist our understanding of the levels and causes of vibrations, and these have reflected similarities across the network. Undertaking this type of monitoring for every resident that complains about road traffic vibration is a costly exercise and is unaffordable.

Monitoring

We have engaged an acoustic consultant (an expert specifically focused on vibrations) to monitor road traffic vibration in residents’ homes. The purpose of the monitoring was to ascertain whether the road traffic vibration had reached a level that adversely impacted a residential dwelling.

Due to the broad range of factors contributing to vibration, monitoring was focused on:

measurement of road traffic vibration levels within residents’ homes that were on a bus route with speed tables
using different sized test buses with drivers travelling through the bus route at varying speeds
measuring the existing speeds of vehicles on the approach to and departure from the speed table
counting the number of heavy vehicles using the street during the monitoring of road traffic vibration levels
a qualitative survey of 3 bus passengers at the front, centre and rear seats of the test buses

Summarised findings

The monitored road traffic vibration levels have been found to be at an acceptable level and did not reach a threshold level that is known to cause damage to a residential building.

The perception of road traffic vibration varies between people and while few people can feel low vibration levels, most people do not feel road traffic vibration or find it a nuisance. This is observed on roads other than the test road where a single resident raises road traffic vibration concerns and other residents have not.
An uneven road surface or road surface imperfections on the road is a contributing factor to road traffic vibration. This can be exacerbated when heavy vehicles travel over these imperfections at higher than average speeds.
Higher speeds of heavier vehicles resulted in higher monitored road traffic vibration levels; however, the vibration levels were still below the threshold for property damage.
The passenger at the rear of the bus consistently experienced the worst comfort out of the 3 passengers when the bus driver travelled at higher than usual travel speeds.

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