Reliable techniques have been used in a number of countries throughout the world for some years now for the prediction, measurement, assessment and control of road traffic noise.
Techniques for the prediction of traffic noise are all based on the assumption that traffic is freely flowing. In many cases when the traffic flow is interrupted, for example in the vicinity of intersections, this assumption is invalid and the established techniques are generally unsuitable.
This report concentrates on the generation of traffic noise under interrupted flow conditions.
A comparison of traffic noise from freely flowing traffic conditions and traffic noise produced by interrupted traffic flow conditions identifies the complex nature of interrupted traffic flow noise.
This leads to a definition of the important features of a prediction model for interrupted flow.
Part of the problem in developing a noise prediction mode for these situations is the need to adequately describe the traffic flow characteristics.
Models for the prediction of interrupted flow traffic noise can best be developed for use at signalised intersections because of the certainty of data on the timing of traffic flows by obervation of signal phasing.
This report reviews in some detail current technology as published in the literature, and recommends the adoption of a suitable model for further trials under New Zealand conditions.
Preliminary trials at two intersections in Wellington show the performance of the model is improved by using vehicle source noise levels representative of the New Zealand vehicle fleet because source noise levels relating to Australian conditions where the model was developed are different.
The model is useful in the prediction of noise levels for future situations where signals are to be installed, or where changes in signal phasing are planned.
For existing situations, the model is a cost-effective method of determining noise levels at signalised intersections, when compared with manual survey methods.
In the longer term it is possible that the model can be used to investigate the optimum phasing of networks of signalised intersections so that the overall noise emission is reduced. Improvements to reduce noise emission may also reduce other emissions from the traffic stream.
Keywords: Traffic, noise, prediction, interrupted flow, model, roads, Australia, New Zealand