It is a generally accepted principle that our environment must be protected in order to preserve human health and quality of life, and to maintain the diversity of species and the reproductive capacity of the ecosystem as a basic resource for life. Large development projects may have adverse effects on the environment, and the relevant authorities make judgements about such effects when scrutinizing the proposals before granting permission to proceed. The developer is therefore required to submit, with the planning application, a statement of an assessment of the environmental impact of the development proposed, together with a description of mitigating measures.
The types of project and the environmental factors which they affect are many and varied. One of the most frequent categories of development for which EIARs are produced is the construction of roads and motorways, in which it is mandatory to consider the effects of a major development on ambient noise levels. We may take as a fairly typical example, the planning of a new motorway, together with the development of the area through which it passes. The developers need to be able to identify alternative routes for the road which do not substantially affect existing development in terms of the amount of noise generated, and they need to determine the appropriate areas for new housing development which fall outside the envelope of unacceptable noise level due to the road.