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Latest Trends on Urban Planning and Transportationand simple way. In addition, for each noise map(Lden, Lngt) is created a conflict map (Fig. 14).Conflict maps show the difference between thepredicted noise level and the noise limits (70dB forLden, 60dB for Lngt).Using the noise maps and the conflict maps ispossible to identify the hot spots and also the quietareas, and to estimate the number of annoyed peoplefor Lden and Lngt. The quiet areas are defined asareas of at least 4.5 hectares with a maximum noiselevel of 55 dB. In order to identify these areas, it isfirst necessary to convert the grid cells of the noisemap in noise surfaces. Technically, all the points ofthe grid cells must be converted in squares and thesquares of the same color will compose a surface(the object type is region). Then the regions areconverted in closed polylines. The area of a regionor closed polylines can be obtained using standardAutoCAD requests. Only the contours with an areagreater than 4.5 hectares and a corresponding noiselevel of less than 55 dB are maintained. An exampleis given in (Fig. 8). Only those quiet areas placed inresidential areas will be taken into consideration.Here another problem was identified: if the trafficvolume and speed for residential streets are usedaccording to [14] and [15], the noise level on thestreets is over 55 dB and these streets interfere withsome possible quiet residential areas.In this phase all the necessary data for ascertainingthe number of people exposed to various noise levelsare established. For each building is known thenumber of inhabitants (stored as metadata). From thenoise map is possible to identify the exposure ofeach façade of the building to each noise level (Fig.10). The grid cells are colored according to theequivalent noise level (intervals of 5 dB). The exactnoise value is stored as Z coordinate of the cell;adding this value as metadata is not a good ideabecause the very high number of cells will make theexecution of any other command very slow.Fig.10 - Exposure of the facadesThe first step is to find all the intersections betweenthe building contour lines and the squaresrepresenting the grid cells in the noise map. Only thex, y coordinates are used to calculate theintersections, because z is the noise value. For eachintersection found the value of the noise associatedto the respective grid cell is added to a list – theblack list in (Fig. 11). This list is added to thebuilding object in the drawing as metadata.Fig.11 - Metadata associated to a residential buildingFig.8 - Example of a “quiet” area identified: morethan 9 ha under 55 dB, over 500 inhabitantsIn the second phase, it is calculated the number ofinhabitants exposed to each 5dB interval of noiselevel, then these values are added to the list ofexposed people (see Fig. 12).Fig.12 - People exposed to different noise levels,calculation resultFig.9 - Noise maps; source: road traffic - Lden (left),Lngt (right)Based on these results, difficult to read andunderstand for most people, are created the chartsshown in (Fig. 13). The red bars represent the peopleexposed to a noise level higher than the limitallowed for the respective period (day or night).These red bars are in direct relation with the areasmarked in the conflict maps.ISSN: 1792-4286 89 ISBN: 978-960-474-204-2
Latest Trends on Urban Planning and TransportationThe measures which lead us to the difference map in(Fig. 15) are related only to the road surfaceconstruction of the main streets. Other globalmeasures, with significant effects, are difficult to betaken. A detail view of the original and the updatednoise maps is given in figure 16.Fig.13 - People exposed to different noise levels,chartFig.15 - Example of a difference mapFig.14 - Part of a conflict map (road traffic noise),detailThe colors used in the conflict maps are: green for anoise level with maximum 5 dB lower than the limit(in Romania the limit for the noise generated by theroad traffic is 70 dB for day/evening/night and 60dB for night); red is for a noise level with maximum5 dB higher than the limit and blue is for a noiselevel of more than 5 dB over the admitted limit.Based on the conflict maps and the number ofpeople exposed to high noise level, the localauthorities should propose action plans for reducingthe noise level and its effect on the population.Taken into consideration the proposed measures,new noise maps can be created and, again, thenumber of people exposed to high noise levels canbe ascertained. From the initial and the estimatednoise maps it can be generated the difference maps,like the one shown in (Fig. 15). The color scale ofdifference maps is for intervals of 1dB; in the givenexample orange means no change (0 dB), greenmeans a gain of 3-4 dB.Fig.16 - Details of the initial and after noise mapIn the map on bottom half of figure 16, the intenseblue color (the highest level of noise) was disappearand, in general near the main streets, each color isturned into the next lower level. There are nochanges across the buildings which are not close tothe main roads, because the secondary roads werenot affected by the proposed measures.The difference maps and the noise maps post- actionplans are just what could be, not what will be. Onlythe representatives of the local authorities can decideISSN: 1792-4286 90 ISBN: 978-960-474-204-2
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