The document was produced by the Department of the Environment and the Welsh Office in 1988 and provides the method of calculating (and measuring) road traffic noise levels for new and altered highways. The document is referred to as the method of assessment to be used in the Noise Insulation Regulations. However, the document is also used for carrying out road traffic noise assessments for planning purposes in relation to Design Manual for Roads and Bridges as well as developments such as housing sites adjacent to existing and proposed roads.
The prediction method calculates the source noise from road traffic by taking in to account the traffic volume, percentage of heavy vehicles, speed, gradient and road surface type. The screening effects of any barriers, buildings and ground contours are assessed along with distance attenuation. Finally any reflection effects are considered, and the combined noise level at a given point is calculated for all the roads affecting the receptor.