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Noise register of road traffic
Noise nuisance caused by road traffic was modelled in 2006: the contours of the annual noise levels that exceed 45 dB(A) are indicated on the map of the noise situation of the regional territory. Due to the dense road network most of the Brussels territory is exposed to the noise impact from road traffic. The highest noise levels are recorded along the main axes and in the areas adjacent to these. Nevertheless, there are also quieter areas with an isolated location within housing blocks or in the midst of little developed areas (parks, fallow land, forest).
Road traffic on the rise
According to the estimates of the FPS Mobility and Transport for 2006 3.81 billion vehicle kilometres were travelled on the Brussels road network, 73% of which on the regional road network.
This number has been increasing almost continuously since 1985 (that year 2.77 billion vehicle kilometres were travelled). More recent estimates, however, suggest a decrease in the number of kilometres travelled since 2007 (3.77 billion vehicle kilometres in 2010).
Assessment of noise from road traffic
To assess the noise nuisance in the nearby environment of the inhabitants of Brussels an 'acoustic' site description of the territory was made in 2006. The purpose of this site description is to quantify the 'structural' noise from road traffic and to create a model of the nuisance experienced by the population. The maps resulting from this modelling are called the 'noise register of road traffic'.
This register determines the Lden (Level day-evening-night), on the one hand, and the Ln (Level night), on the other. Lden represents the weighted equivalent noise level over 24 hours that was observed on average for an entire year (in this case 2006). For the weighting a penalty factor of 5 dB(A) is applied during the evening hours (7:00 p.m. to 11:00 p.m.) and of 10 dB(A) during the night (11:00 p.m. to 7:00 a.m.), as noise at those times is experienced as a greater nuisance. Thanks to the weighting in accordance with the period of the 'day', this indicator reflects quite accurately the real noise nuisance experienced by the population. Ln (Level night) represents the noise level during the night (11:00 p.m. to 7:00 a.m.).
Severity of noise nuisance from road traffic
Noise register of road traffic in the Brussels Capital Region – Indicator Lden
Sources: Bruxelles Environnement-Leefmilieu Brussel and Acouphen Environnement, 2010, ' Geluidshinder door het verkeer – Strategische kaart voor het Brussels Hoofdstedelijk Gewest ', based on the traffic data for 2006, the NMPB-Routes-1996 method and modelling software CadnaA
Due to the density of the road network the impact of the noise from road traffic is felt throughout most of the Brussels territory. On most main axes and in the surroundings of those axes the 55 dB(A) level is exceeded. Even so, there are also more remote, quieter areas within residential clusters or in the middle of little developed areas (parks, fallow land, forest).
As for the highest noise levels (Lden above 55 dB(A)), two situations occur depending on whether there is continuous development along the traffic axes which can partly prevent the noise from spreading:
- When there are few obstacles that can prevent the spreading of the noise, very high levels (Lden between 65 and 75 dB(A)) are recorded on the axes themselves and in the adjacent areas. This is specifically the case for the motorways and the city's main axes leading to the A12 to Antwerp, the A3/E40 to Liège, and the A4/E411 to Namur; for the Western Ring Road near Anderlecht and Forest and for the Eastern Ring Road in Auderghem and Neder-Over-Heembeek. The same applies to the approach roads to the city, such as Avenue de Vilvorde-Chaussée de Vilvorde, Avenue Léopold III, Boulevard de la Woluwe, Avenue de Tervueren, Chaussée de Wavre, Avenue de la Foresterie, Drève de Lorraine, Boulevard Industriel, Boulevard Henri Simonet, Avenue Charles-Quint, Avenue de l'Exposition and Avenue Van Praet. In the large city parks, such as Bois de la Cambre and Parc du Cinquantenaire, or around the Sonian Forest and the large green areas (such as the Royal Park and the parks of Pede) high levels are recorded as well (Lden between 55 and 60 dB(A)).
- The noise nuisance along axes bordered by continuous development is mainly concentrated on the axes themselves, thanks to the screen provided by the buildings. Although very high levels (Lden higher than 65 dB(A)) are observed on the Inner and Outer Ring Road and on numerous secondary axes, the levels in the immediate surroundings of these normally do not exceed 55 dB(A).
As a result, two large areas can be distinguished: on the one hand, the centre of the Region, characterised by a high population density but also by dense, continuous development which often prevents the noise from spreading and, on the other hand, the less densely populated outskirts of the Region, where the noise of the traffic axes is able to spread more easily and the nuisance is often felt at great distances from those axes.
At night, the levels observed drop by approximately 10 dB(A) compared to day-time, and stay below the level of Ln 45 dB(A) in most of the territory (i.e. the threshold considered to be moderately to severely sleep-disturbing by the WHO). However, in the immediate surroundings of the roads that were included in the study, levels are still too high; this is especially the case in the vicinity of the Eastern and Western Ring Road, the area around the Inner and Middle Ring Road (between 65 and 75 dB(A)) and the approach roads (between 60 and 70 dB(A)).
Road traffic occupies the first place when it comes to noise nuisance caused by traffic
Within the share that can be attributed to all forms of transport in the average total urban noise, the noise caused by road traffic is far ahead of other modes of transport (rail and air traffic, trams and underground trains) when expressed in terms of the number of residents exposed.
We wish to emphasise that these conclusions are based on a model on the scale of the Region and are representative of the situation over a whole year. Furthermore the model does not take into account all traffic axes.
- Acouphen Environnement, 2009, 'Impact acoustique des transports terrestres pour la Région de Bruxelles-Capitale', study commissioned by Bruxelles Environnement-Leefmilieu Brussel, final report, 303 pages