How were the maps made?
The noise maps have been made using computer modelling techniques, based on information such as traffic flow data, road/rail type, and vehicle type data. No actual noise measurements have been made in the production of these strategic maps. The modelling, where necessary, also took account of features which affect the spread of noise such as buildings and the shape of the ground (e.g. earth mounds), and whether the ground is acoustically absorbent (e.g. fields) or reflective ( e.g. concrete or water). The calculations produced noise level results on a 10m grid at a receptor height of 4m above ground, as required by the END and the Regulations.
The data required for the calculations of noise levels have been collated in liaison with various organisations including the Department for Transport, Highways Agency, Network Rail, various airport operators, and the Environment Agency.
How accurate are the maps?
The noise maps have been produced for use at a strategic level and give an acceptable level of accuracy for these purposes. They will not however necessarily properly represent the situation at a local level and the results of the noise mapping should not be used alone for any land use planning or location-specific assessments.