Strategic noise map type A according to indicator Ln (night). Prefectural Order No 71-2018-07-13-005 of 13 July 2018.

The European Directive 2002/49/EC on the assessment and management of environmental noise aims at a harmonised assessment of exposure to noise in the Member States. It defines them as representations of data describing a noise situation according to a noise indicator, indicating exceedances of limit values, the number of persons exposed. Noise maps are not prescriptive. These are information documents that are not legally enforceable. As graphic elements, however, they can supplement a Local Planning Plan (LDP). As part of an Urban Travel Plan (UDP), maps can be used to establish baselines and target areas where better traffic management is needed. To quantify the level of noise emitted by an infrastructure over an average day, two indices are used, the Lden index and the Ln index, recommended for all modes of transport at European level: Lden: representative indicator of the average level over all 24 hours of the day, LN: representative indicator of the average sound level for the period 22h-6h. Noise levels are assessed using digital models (computer software) incorporating the main parameters that influence noise and its propagation (traffic data, field topology, meteorological data, etc.). The noise maps thus produced are then cross-checked with the demographic data of the areas concerned in order to make an estimate of the population exposed to noise pollution. The noise level shown on the noise maps is derived from a calculation method which gives approximate values and often higher than reality (maximists) in a noise area considered critical. An in situ noise control can determine precisely the noise to which a construction and its occupants may be exposed. The map of the Ln exhibition areas (type A map) represents the areas exposed to more than 50 dB in Ln according to the prefectural sound classification orders issued pursuant to the Ministerial Order of 30 May 1996 and based on a forecast evolution of traffic.