Noise impact assessments in early stage road and railway planning

During early route planning of a new road or railway, several potential routes are considered and evaluated. The route selection assessment, also referred to as optioneering, requires input from various specialists to evaluate strengths and weaknesses of a potential route. The assessment is associated with many constraints, such as construction costs, geometric design, visual amenity and environmental effects. Noise impact assessments, however, are challenging to take into account at such an early stage due to time consuming modelling and calculation procedures that depend on a predefined route. In this study, a new and simplified noise impact assessment procedure, based on the reciprocity principle, is presented. By placing point sources on dwellings and receivers in a grid over the area of interest, the resulting noise map displays the potential noise impact of all grid points. A pathfinding algorithm that traverse the quietest points in the map determines the optimal route with minimal noise impact. Furthermore, as it does not depend on a predefined route, it is a flexible and useful tool for prioritizing multiple routes during early planning stages. A case-study is presented and a comparison between the proposed procedure and the common noise impact assessment is carried out and discussed.