19 th INTERNATIONAL CONGRESS ON ACOUSTICS MADRID, 2-7 SEPTEMBER 2007 LARGE SCALE NOISE MAPPING IN ALPINE VALLEYS WITH MITHRA-SIG

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1 19 th INTERNATIONAL CONGRESS ON ACOUSTICS MADRID, 2-7 SEPTEMBER 2007 LARGE SCALE NOISE MAPPING IN ALPINE VALLEYS WITH MITHRA-SIG PACS: 4.50.Rq Baulac, Marine 1 ; Defrance, Jérôme 1 ; Olny, Xavier 2 ; Miège, Bernard 2 ; Yvon, Claude 1 CSTB, 24 rue Joseph Fourier, 8400 Saint Martin d Hères, France; marine.baulac@cstb.fr 2 CETE, 46 rue Saint Théobald, BP 128, 8081 L Isle d Abeau cedex, France GEOMOD, La galaxie, 89 rue de la Villette, 6900 Lyon, France ABSTRACT ALPNAP is a project funded by the Alpine Space programme of the INTERREG IIIB community initiative of the European Union. This project deals with moniring and minimisation of trafficinduced noise and air pollution along major alpine transport routes. This paper concerns the acoustical part and explains how large scale noise maps are created. The software MITHRA- SIG is used for the acoustical simulations; this ol is a combination between MITHRA, a powerful code based on fast ray tracing and dedicated outdoor noise level predictions in complex environments, and the Geographical Information System SIS (Spatial Information System). Specificities of alpine valleys are taken in account for calculations including meteorological effects. Input traffic data come from measurements in the valley and represent the year Other realistic scenarios are also considered and compared. Finally, acoustical results for those different cases are given and discussed. The global impact assessment of both noise and air pollution is also planed be achieved within the ALPNAP project. 1. INTRODUCTION ALPNAP [1] is an EU funded project in the INTERREG IIIB Alpine Space programme [2]. The - year project started in January It unites 11 partners from 4 countries (Germany, Austria, Italy, France) form an Alpine wide network of experts in the fields of Alpine meteorology, air pollution, noise, and health effects. This project deals with moniring and minimisation of trafficinduced noise and air pollution along major alpine transport routes. Two major Alpine transit corridors are studied in the ALPNAP project: the Fréjus corridor linking Lyon in France with Turin in Italy and the Brenner corridor linking Munich in Germany with Verona in Italy. In both corridors there are roads and railways. This paper deals with large scale noise mapping in the Alps within the project ALPNAP. Acoustical simulations are achieved with the powerful software MITHRA-SIG. Three areas are concerned with large scale noise mapping: the Maurienne valley and the Susa valley on each side of the Fréjus corridor and the lower Inn valley in the Brenner corridor. The aim is obtain noise levels on building façades in order determine the noise exposure for population. Horizontal noise maps are also achieved for visual representation. The global impact assessment of both air and noise pollution is planned be evaluated as a final result of the project. This paper is divided in three parts. First, the software MITHRA-SIG is briefly described. Then, the data processing is presented with specification of which input data is required. After that, an example of large scale noise mapping is presented with different steps from the beginning (the data) the results (the noise maps). Finally, a conclusion will give an overview of the results and the perspectives expected. 2. MITHRA-SIG SOFTWARE MITHRA is a powerful code developed about fifteen years ago by CSTB and dedicated outdoor noise level predictions in complex environments []. It is based on a fast ray-tracing algorithm. The standard methods used are either the IOSO or the NMPB (The French

2 method which is the proposed interim computation methods for road traffic noise in the European Noise Directive 2002/49/EC). For large scale noise mapping, a version of MITHRA coupled with the Geographical Information System SIS (Spatial Information System) is used. This complete software is named MITHRA- SIG and is developed, for the acoustical part, by CSTB and for other elements by GEOMOD. MITHRA-SIG gives the opportunity of investigating traffic noise propagation on a whole Alpine valley. For ALPNAP purposes, only the NMPB will be used with application of specific local long term meteorological occurrences of conditions favourable noise propagation.. INPUT DATA The data processing is an important part of computing large scale noise maps. Input data can be divided in three categories: geographical data, traffic data and meteorological data. Those three kinds of input data are detailed in this section..1. Geographical data A first step concerns the preparation of geographical data. Input data are D databases from IGN (national geographical institute in France) giving relief, buildings, roads, railways. This data has be cleaned in order delete inconsistencies (points set height 0 for example, or double points). Then, roads and railways have be separated in sections according traffic data. Tunnels and bridges are kept with different properties since there specificities play a role in the acoustic processing. Noise barriers are also considered..2. Traffic data The traffic data is needed have accurate acoustical simulations. For the French side of the Frejus corridor permanent traffic counting stations or ll systems, managed either by Société Française du Tunnel Routier du Fréjus SFTRF (the French highway A4 manager), or the Direction Départementale de l'equipement de la Savoie DDE7 (the French national roads RN6 and RD902 manager) have been used acquire the required information. On the Italian side of the Frejus corridor data have been obtained from traffic modelling based on punctual traffic counters. Those traffic data represent the year The traffic data is: the number of light vehicles, the number of heavy vehicles and their speeds for roads and the number of trains, their description and their speeds for railways. Morways, main roads and main railways are divided in several sections where the traffic data is specified for the three periods day / evening / night. In order make simulations as accurate as possible, some measurements of road pavements properties have been carried out and taken in account for the achievement of noise maps. Different realistic scenarios are planed be evaluated. This part is related with the MONITRAF project, another INTERREG Alpine Space project. Scenarios deal with BAU (Business As Usual) increase of traffic, reduction of speed, modal shift or removal of some classes of trucks... Meteorological data The meteorological conditions have a significant influence on noise propagation, especially in mountainous areas. For the software MITHRA-SIG, the input data required is the percentage of favourable conditions depending on the direction of propagation and the period (day / evening / night). Those percentages are calculated from measurements of wind speed, wind direction and temperature. 4. EXAMPLE In this section, an example of large scale noise map is presented. It is a part of the Maurienne valley. The meteorological conditions and measurements of the road pavement properties are not taken in account at the moment Input data The Maurienne valley is presented in figure 1. Green lines corresponds the relief; blue lines morways, red lines national roads and black lines main railways. The area considered in this section is the one delimited by the thick grey line. Figure 2 gives a D view of the valley with main transport routes and also with buildings (in beige). 2

3 10 km Figure 1: The Maurienne Valley and the area of study (thick grey line) Figure 2: D view of the Maurienne Valley Parameter HV day HV evening HV night LV day LV evening LV night Speed PV Speed LV Value Parameter FRET day FRET evening FRET night Speed FRET HLP day HLP evening HLP night Speed HLP TGV day TGV evening TGV night Speed TGV Value (a) Parameter TER day TER evening TER night Speed TER Z2 day Z2 evening Z2 night Speed Z2 MESSAGERIE day MESSAGERIE evening MESSAGERIE night Speed MESSAGERIE Value (b) Figure : Example of traffic data for (a) mor ways and national roads, (b) for railways. HV = Heavy Vehicles, LV = Light Vehicles. FRET, HLP, TGV, TER, Z2 and MESSAGERIE are names of different kinds of trains. 19th INTERNATIONAL CONGRESS ON ACOUSTICS ICA2007MADRID

4 4.2. Results There are two main kinds of results: horizontal maps and D façades results: - Horizontal maps: calculations at a specified height of a chosen acoustical indicar (L den, L eq, L day, etc.) and representation with a scale of colours. - Receivers in facades: calculations for receivers located 2 m away from each facades (the number of receivers for each facades depends on some parameters specified). Several acoustical indicars can be calculated. This kind of results, when related population data, allows evaluate the exposed population (according the European Directive). For receivers in façades, the last façade reflection is not taken in account as recommended for strategic noise maps asked by the European Directive. Figure 4 give D façades L den values for traffic data of The acoustical indicar L den is given by equation (1); levels for periods evening and night are raised by 5 and 10 db in order take in account the increase of bother. = (Eq. 1) Figure 4: D façades noise map giving L den Figure 5 is a representation of buildings which are coloured depending on the maximum level calculated (taking all façades and all floors of the building). Figure 5: Building coloured noise map (façade Sound Pressure Levels) 4

5 Figure 6 gives a horizontal noise map of L den levels at a height of 4 m for the traffic data of The legend is given in db on the right of the figure; it is the one used for figures 6 and 7. L den in db Figure 6: Horizontal noise map of Maximum L den Figure 7 gives two horizontal noise maps of L den levels at a height of 4 m. One (a) is for the traffic data of the year 2004 and the second one (b) is for another scenario which induces a reduction of speed on morways (from 10 km/h 110 km/h). The difference between those two maps is presented in figure 8. Figure 7: Horizontal noise map of Maximum L den 5

6 4.. Discussion One can see in figure 8 that considering another traffic scenario (here a reduction of the speed limit on morways) induces changes in the noise levels as expected. The differences are here not very high but considering more complicated scenarios like modal shift for example, the impact on noise levels and on the population exposure will certainly be more significant. More scenarios have now be studied in order get more representative impact of altering traffic data Figure 8: Differences in db between the two maps of figure 7 (impact of changing the speed) 5. CONCLUSIONS The main goal of the project ALPNAP is evaluation the global impact assessment of both noise and air pollution. Here, the way obtain large scale noise maps has been presented. Even if there is much work left do for the project, those preliminary calculations have shown the interest of data processing and large scale noise mapping. Work is still in progress in order take in account the meteorological effects and the road pavement properties measurements and achieve large scale noise mapping on the whole three areas of interest. Those large scale noise maps will be achieved by the use of MITHRA- SIG. Finally, those results concerning noise propagation in alpine valley are supposed be combined with simulations of air pollution propagation in order have the global impact assessment. References: [1] [2] [] Y. Gabillet, D. Van Maercke, Outdoor noise propagation in urban areas: principles and use of the MITHRA software. Euronoise. Lyon, France. (1995) 6