Strategic noise mapping of major roads in Ireland - A centralised approach

As specified in the Environmental Noise Regulations (S.I. No. 140 of 2006), which transposed the EU Environmental Noise Directive into Irish law, the National Roads Authority (NRA) now Transport Infrastructure Ireland (TII) are required to prepare strategic noise maps for all major roads classified as national roads. The responsibility for mapping non-national major roads lies with the relevant local authority within whose functional area the road resides. Therefore, over 25 different authorities have mapping responsibilities in Ireland. This has the potential to lead to an inconsistent approach to the mapping of Major Roads outside agglomerations. Furthermore, the approach opens up the possibility of 'double-counting' in population exposure assessments. In January 2012 a "Centralised Approach" was agreed for Phase II mapping and the NRA, as lead body, prepared maps for over 4,000km of national and non-national roads. Noise calculations performed at this time were the most complex and detailed assessments ever conducted in Ireland. In order to deliver the maps in a timely manner, a number of modelling efficiencies were utilised including the development of a variable grid model to reduce model run time. Whilst the "Centralised Approach" worked very well, a number of key "lessons learned" were identified. Quality control and data clean-up was required on most local authority data sets and uncertainty surrounding which local authority had roads exceeding the threshold existed.