Planning policy guideline PPG24 provides Noise Exposure Categories (NEC’s) to assist local planning authorities in assessing new residential developments alongside existing transport related noise sources. The categories A to D define noise level ranges for different noise sources.
Category A represents circumstances in which noise need not be considered a determining factor; category B applies to the situation where noise should be taken into account; category C covers noise levels where planning permission should not normally be granted and category D is for planning permission refusal.
PPG24 has previously been used to assess road traffic, railway & aircraft noise across residential development sites, but was withdrawn in 2012 as part of the Government's National Framework Initiative. Nevertheless many Local Authorities have chosen to continue with some form of PPG24 noise exposure categories to assess sites. If industrial noise is present then a BS 4142 assessment is also necessary.
Traffic noise predictions are normally conducted in accordance with the Department of Transport CRTN method. This method takes into account the speed and flow of the traffic, the road gradient, HGV content, source and reception point heights, perpendicular distances to noise source line etc, plus any barrier attenuation or ground absorption effects on route.
The Department of Transport’s Calculation of Railway Noise report provides a method of predicting railway noise levels based on a knowledge of train types, train speed, numbers of locomotives and carriages, state of track and ballast, intervening ground cover, site layout etc. It is primarily intended for the assessment of sound insulation requirements for new railways, but can also provide guidance in land use planning near existing railways.
PPG24 assessments (either by measurement or prediction) combined with BS 4142 assessments (where necessary) can be carried out and followed up with general design recommendations for window glazing selection, fence/wall attenuation etc.
During 2003 JSP consultants assisted Mouchel Consulting Group and Transport for London on the A406 London North Circular Road Improvement scheme by way of base line noise surveys, traffic noise predictions in accordance with DMRB procedures, including identification of noise sensitive properties and the classification of noise nuisance areas.