Many road designations have conditions with respect to noise that require that when the road is completed, measurements will be undertaken to prove that the performance standards of those conditions have been fulfilled. However all measurements are subject to variability, and the designation conditions do not address either the expected nature of this variability, or how it should be accounted for in establishing compliance with the conditions.
This research was carried out in New Zealand between 2006 and 2008. It sought to quantify the variability in noise measurement, and then in light of this identified variability, develop a recommended approach to establishing compliance.
This report first discusses the evolution of current practice, and then examines in detail the expected variability that can occur both in noise generation and noise propagation. The impact on noise levels of factors such as traffic volume, HGV, traffic speed, road type, road deterioration, wind speed and direction, ground type and vegetation is examined. Recommendations to improve measurement consistency are made.
The recommended method of compliance that is advanced is based on noise modelling, supplemented by measurement, to validate the overall model, followed by testing the performance of noise mitigation elements that are incorporated in the modelling.