The three methods of calculating population exposure according to CNOSSOS-EU

Erwin Hartog van Banda 1

DGMR Software / Softnoise Casuariestraat 5, Den Haag – The Netherlands

ABSTRACT In December 2020, the EU commission published amendments on CNOSSOS-EU in report ‘C(2020) 9101 final’. In this report an additional method for the calculation of population exposure is described, based on a Median value. In the original CNOSSOS document, 2 methods are described, Method 1 – Most exposed façade and Method 2 – Length of representative façade. Method 1 is used for buildings that represent a single dwelling or 1 dwelling per floor. Method 2 is used for apartment buildings that have dwellings with a single façade exposed to noise. The new Method 3 can be used for apartment buildings that have more than 1 façade exposed to noise, or for apartment buildings where no information on how many facades are exposed to noise is available. It will be difficult for authorities to create a dataset that distinguishes between a single façade and multiple façades exposed to noise. Therefore, it seems likely that Method 3 will be more frequently used. When comparing Methods 2 and 3, it is found that Method 3 leads to a higher number of exposed people and dwellings. In this paper the 3 methods are explained and compared using noise and population data for a city in Europe.

1. INTRODUCTION

In 2022 all EU member states are obliged to use CNOSSOS-EU [1] for their strategic noise mapping projects. A strategic noise mapping project starts with getting GIS data of the area involved. This includes data for buildings, roads, railways, industry etc. This data is then imported into a noise mapping software. The next step is to create and calculate receiver points around the facades of residential buildings and assign these noise levels to the people and dwellings of these residential buildings. In this way the population exposure in number of people and dwellings in 5 dB noise classes can be determined. These numbers will then be reported to the EU commission.

This paper starts with a general overview of the project flow of a CNOSSOS-EU noise mapping project, then shortly describes the 2 methods for creating the receiver points and then explains the 3 methods on determination of the population exposure.

Finally the 3 methods on determination of the population exposure are compared using noise and population data for a city in Europe.

1 ha@dgmr.nl

Wr 3) sax al a. inter noise 21-24 AUGUST SCOTTISH EVENT CAMPUS ? O ? ? GLASGOW

2. PROJECT FLOW CNOSSOS-EU NOISE MAPPING PROJECT

In Figure 1 a possible project flow for a strategic noise mapping project is presented.

Figure 1: Project flow CNOSSOS-EU noise mapping project

In the following chapters step 2 (Create Receivers at Façades) and step 6 (EU population exposure) are further explained

3. CREATE RECEIVERS AT FACADES

The first step on determination of the noise exposure is to calculate the noise levels for receivers that are located at 0.1 m in front of the facades of residential buildings. CNOSSOS presents 2 cases, Case 1 and Case 2, on how to create these receivers points. In Case 1 façades are split up in regular intervals on each façade with a maximum distance of 5 meter. Receiver points are placed in the middle of each interval. In Case 2 façades are split up at set distance of 5 meter from start of polygon, with a receiver point placed at the halfway distance of the 5 meter distance and halfway the remaining distance. In Figure 2 examples of each case are presented.

Figure 2: Examples of location of receiver points around a building following Case 1 (left) and Case 2 (right) procedures

CNOSSOS does not provide further information on when to apply Case 1 or Case 2. For this paper we have used Case 1.

GIs Noise maping software HP files Buildings + Roads + Ground cover Address points + Height lines SI Main model Calculate tiles Main model 1. Import is 5. Import tiles in main model 2. Create Receivers at 6. EU population facades exposure 3. Tile main 4. Local Calculation | |7. Export to model or Cloud Calculation Excel/GIS Excel / GIS NOISE EXPOSURE Cloud Calculation

4. THE THREE METHODS OF CALCULATING POPULATION EXPOSURE

After calculating the noise levels at the receivers these noise levels must be assigned to dwellings and people. The CNOSSOS method describes 3 methods for assigning dwellings and people to receiver points.

Method 1: Most exposed facade “ Where information on the location of dwellings within building footprints is available, that dwelling and the people living in that dwelling are assigned to the receiver point at the most exposed façade of that dwelling. For example, for detached houses, for semi-detached and terrace houses, or apartment buildings, where the internal division of the building is known, or for buildings with a floor size that indicates a single dwelling per floor level, or for buildings with a floor size and height that indicates a single dwelling per building ”.

Method 2: Length of represented facade “ Where no information on the location of dwellings within building footprints as explained above is available, one of the two following methods shall be used, as appropriate, on a building by building basis to estimate the exposure to noise of the dwellings and people in dwellings within the buildings. (a) Available information shows that dwellings are arranged within an apartment building such that they have a single façade exposed to noise

In this case, the allocation of the number of dwellings, and people living in dwellings, to receiver points, shall be weighted by the length of the represented façade according to the procedure under either Case 1 or Case 2, so that the sum of all receiver points represents the total number of dwellings and people living in dwellings assigned to the building .”

Method 3: Median value “(b) Available information shows that dwellings are arranged within an apartment building such that they have more than one façade exposed to noise, or no information is available on how many facades of the dwellings are exposed to noise.

In this case, for each building, the set of associated receiver locations shall be split into a lower and upper half based on the median (1) value of the calculated assessment levels for each building. In case of odd number of receiver points, the procedure is applied excluding the receiver location with the lowest noise level.

For each receiver point in the upper half of the data set, the number of dwellings, and people living in dwellings, shall be distributed equally, so that the sum of all receiver points in the upper half of the data set represents the total number of dwellings and people living in dwellings. No dwellings or people living in dwellings will be assigned to receivers in the lower half of the data set ”

In Figures 3, 4 and 5 these three methods are further explained based on the noise levels on 7 receivers around a residential building that contains 3 dwellings and 5 people. No further information on the layout of the 3 dwellings within the building is known. So it could be 1 dwelling per floor (Method 1 or Method 3) or all 3 dwellings on 1 floor with 1 or multiple façades exposed to noise (Method 2 or Method 3).

=: a Building: 3 dwellings and 5 people ° Method 1: Most exposed facade Maximum = 68 dB(A) for all 3 dwellings and 5 people

Figure 3: Example for Method 1

wo ,

“2 1 Building: 3 dwellings and 5 people .° Method 2: length of representative facade Facade length Lden [m] 1 68 3.37 13.12% Dwellings People 0.39 0.66 98 es Fy as

Figure 4: Example for Method 2

Figure 4 includes a table with the individual façade length per receiver point as calculated according to Case 1. The total number of dwellings and people are then divided over the receiver points depending on the ratio of the individual façade length compared to the total façade length.

NOURWN 68 64 61 59 41 41 Total 3.72 14.49% 3.67 14.29% 3.67 14.29% 3.67 14.29% 3.79 14.76% 3.79 14.76% 25.68 0.43 0.43 0.43 0.43 0.44 0.44 3 0.72 0.71 0.71 0.71 0.74 0.74 5

Figure 5: Example for Method 3

Figure 5 includes a table with the set of values that are used for the exposure. There are an odd number of values so the lowest value (41) is excluded. Then the 3 lowest values (61, 59, 41) of the remaining 6 values are excluded. Each of the 3 remaining highest values (68, 68 and 64) now get 1/3 of the population assigned.

as e ast 1 Building: 3 dwellings and 5 people Method 3: Median value Median Lden values Dwellings People 1 68 68 1.00 1.67 2 68 68 1.00 1.67

In Table 1 the number of exposed people are compared for the 3 methods.

Table 1: Number of exposed people per Lden noise class for 1 building with 3 dwellings and 5 people

Method <=54 55-59 60-64 65-69 70-74 >=75

1 0 0 0 5 0 0

2 1.5 0.7 1.4 1.4 0 0

3 0 0 1.7 3.3 0 0

It is obvious that method 1 will always lead to the highest exposure. When comparing method 2 and method 3 it is also obvious that method 3 will lead to a higher exposure then method 2 because the lowest noise levels are not used and all (dwellings and) people are assigned to the highest half of noise levels.

5. EXAMPLE POPULATION EXPOSURE FOR A LARGE AREA.

For the purpose of this paper an example noise map for road traffic noise for a city in Europe has been calculated using CNOSSOS-EU. In Figure 6 the map with the calculated Lden noise contours is shown. In Table 2 the number of exposed people is presented for the three methods.

Ss 1.67 1.00 64 61 59 go 3 mtn oN Total

Figure 6: Noise map

Table 3: Number of exposed people per Lden noise class for the example area

Method <=54 55-59 60-64 65-69 70-74 >=75

1 19117 7155 29407 17567 305 0

2 43440 9350 14149 6486 124 0

3 23557 11026 26183 12485 240 0

Mixed 31000 10032 21767 10570 160 0

Here we see the same trend as for the single building in Chapter 4. When all buildings are handled with the same Method, Method 1 gives the highest exposure followed by Method 3 and then Method 2.

In order to calculate a more precise number of exposed people, assumptions have been made on the layout of the dwellings in each residential building based on number of dwellings, floor size and height. In this way the building type was determined and assigned to Method 1, 2 or 3 accordingly. The effect on the number of exposed people is shown in Table 3 as ‘Mixed’ method. Note that the results of the Mixed method are in between those of Method 2 and Method 3.

6. CONCLUSIONS

According to CNOSSOS-EU there are 3 methods of assignment of noise levels to population. These methods are based on the type of building. When it is assumed that it will be difficult for authorities

to create a dataset that distinguishes between a single façade and multiple façades exposed to noise, Method 3 is recommended to use as a default. Compared to Method 2 this will push the exposed dwellings and people to the higher noise classes.

7. REFERENCES

1. CNOSSOS-EU method, https://eur-lex.europa.eu/eli/dir/2002/49/2021-07-29 (2021).