Road-traffic noise contours, 1 dB intervals, 50 – 75 dB L_Aeq(24h). Polygon.

These road-traffic noise contours were generated by AECOM for the TAR 19/01 Social cost (health) cost of land transport noise exposure research project, completed in 2023. The research report contains the noise modelling methodology. The Waka Kotahi noise website answers some frequently asked questions about road-traffic noise.

The contours indicate a predicted external noise level arising from road-traffic noise on state highways and arterial roads. Noise level is quantified in dB L_Aeq(24h) and represents an average noise level over 24-hours. Noise levels have been predicted from traffic data, road properties, and topography; there has been no measurement of sound.

Note that the contours were developed as an input for a cost model, with the purpose of determining noise exposure at the district, region, and national levels. They were not subject to the same level of quality assurance at a local level as predictions made to support assessments of environment effects, for example. The uncertainty for any given location is greater than ± 5 dB at the 95% level of confidence, probably significantly so.