In our bustling urban world, noise is always present. From traffic to construction, it’s infiltrated every aspect of our lives. Beyond inconvenience, noise presents a tangible cost to society; it affects our health, wellbeing and quality of life.
World Health Organisation studies place noise as one of the leading environmental risks for health and wellbeing, after air pollution. Therefore, it’s critical we understand and address environmental noise.
NZTA Waka Kotahi recognised this issue’s significance and engaged AECOM to research the social health costs of land transport noise exposure throughout New Zealand. This collaborative effort, spanning 2020 to 2022, involved experts from New Zealand, Australia and the United Kingdom.
Assessing the health and financial costs of noise
NZTA Waka Kotahi’s primary research aim was to calculate the health-related social and financial costs linked to noise from New Zealand’s road and rail networks.
We developed a matrix of health-related effects caused by noise exposure which laid the foundation for a comprehensive methodology that assessed the costs arising from these impacts. We assessed existing research that informed our methodology to predict and evaluate transport network noise. We identified which health issues are caused by noise, and how much the noise increases the risk of each one. We then created a model to quantify the costs of those health issues caused by noise.
What are the health effects of environmental noise?
Prolonged exposure to high noise levels has proven correlation to a range of stress-related conditions including hypertension, cardiovascular diseases and sleep disorders. Our research specifically explored the impact of noise exposure on annoyance, sleep disturbance and ischaemic heart disease (IHD).
Annoyance, a typical response to noise, encompasses a range of negative emotions, from disturbance and dissatisfaction to distress and irritation. Noise-induced sleep disturbance doesn’t just compromise sleep quality, it can also impact glucose metabolism, memory consolidation and blood vessel function, potentially leading to cardiovascular issues. IHD, linked to narrowed coronary arteries, can manifest as heightened stress reactions, oxidative stress, vascular stiffness and arterial hypertension.
How did we estimate the amount of people affected by noise?
To find this out, we pinpointed dwellings and estimated population counts. Obtaining precise dwelling-building correlations and occupancy figures from available datasets is challenging, so we used an automated approach. We brought together many publicly available data sets including building outlines, land parcel address points and parcel land uses, to estimate which buildings are dwellings, and the corresponding occupancy within each dwelling. We leveraged 2018 Census data, covering 16 regional council areas, 20 health districts and 66 local councils.
How did we model how much noise people are experiencing?
As a critical aspect of the research, we modelled noise using the Calculation of Road Traffic Noise prediction method, which estimates long-term average noise levels from road traffic. We used it within our noise modelling and mapping software that simulates road traffic noise levels over various terrains and layouts. We input detailed 3D data about the shape of the land (like slopes, hills and flat areas) to help calculate how the noise travels. Various other inputs, like building outlines, alignments of state highways and major arterial roads combined with traffic data, and rail alignments with train volume data, enabled comprehensive noise modelling. From this modelling, we estimated the noise levels at each dwelling. Alongside the noise predictions, we generated noise contours for visualising noise emissions, which showed us how the noise spread out from the roads.
How did we model the social cost of noise?
A critical element of the study was formulating a model to assess the social cost of transport noise in relation to identified health effects. Key parameters included counts of the population exposed to each 1dB band of transportation noise, categorised by location and type of transport noise. The model also included disability weightings, which measure the health impact severity for each health issue caused by noise, and calculations of Quality-Adjusted Life Years, which measure the number of years people live in good health.
What is the financial cost of noise in New Zealand?
Through our economic cost modelling, we found the health effects from exposure to road and rail transport noise costs the New Zealand economy approximately $654 million annually. This reflects the impact on community health outcomes spanning both the North and South Islands.
Continued exposure to noise from land transport has the potential to bring about a broad spectrum of negative consequences for health and wellbeing. The primary goal of the research was to gauge and assign a monetary value to these adverse effects and accurately estimate the total financial impact to the New Zealand economy. The findings from the analysis reveal that road-related noise is the leading contributor to financial impact, accounting for approximately $502 million annually, while rail-related noise costs the New Zealand economy approximately $152 million per year.
This study did not quantify several other health-related noise costs due to limited evidence and data availability. As a result, the true extent of the economic impact of road and rail noise on the community is likely to be more substantial than currently estimated.
Read the full study here.