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Application to Areas of Designated Use

The evaluation method is applied to areas of designated land use. This is a simple example.

Area of designated land use with road

Edit dialog of this object (example 1)

Monetary Data (local)

The edit dialog of the residential area shows (see Area of Designated Land Use) that when "Monetary Data" is activated three further values can be entered:

  • Floor/Ground Ratio (NAGFZ)
  • Rental/m²/a (NAMIETE)
  • Rental abatement (NAMIND)

The bracketed abbreviations are the names of variables needed later to perform necessary operations.

In the edit fields for rental abatement in the dialog Area of designated Land Use the two variables

  • LP sound pressure level
  • NA_STR maximum value for noise from road traffic (defined in Options|Land Use|Limiting Value)

are used to express the loss in value for all areas with sound levels within 5 dB under the maximum value.

Floor/ground ratio: A factor when multiplied by the ground area, gives the maximal residential area of buildings permitted on this area.

Rental/m²/a: can be entered in any currency unit. The calculated results are then related to this currency.

The factor in the equation of input line „Rental Abatement“ - 0.01 in the first example - is the loss of rent due to a level increase of 1 dB. 0.01, meaning rentals are reduced by 1% if the level raises 1 dB.

Further variables needed in the expressions of evaluation:

  • FL area of a grid element in m²
  • NAOK logical value (0-false, 1-true) as a definition if a grid element is inside an area of designated land-use or not

Calc Grid

In the first step, to come to a monetary evaluation of the noise, the noise level is calculated on a grid for the whole area.

Evaluate Grid

With the second step the evaluation, with the defined formula in Grid| Evaluation, is calculated for all grid points and the result is added up.

The following results are obtained when using the expressions on the right side. The accuracy depends on the size of the grid elements because a grid element is taken to be in an area if the grid point is located in it. It is, therefore, recommended you use grid spacings as small as possible.

FL Calculation area in m²
FL*NAOK Area of designated land use in m²
FL*NAOK*NAGFZ Total residential area in an area of designated land use
FL*NAOK*NAGFZ*NAMIETE Rental for all areas of designated land use
FL*NAOK*NAGFZ*NAMIETE*NAMIND Reduction in rent due to noise

For example 1:

  • the calculation area (FL) is 10,080 m².
  • The size of the area of designated land use is 8,000 m².
  • The floor/ground ratio is 0.8.

So the maximal residential area on this estate is 0.8 x 8,000 m² = 6,400 m². The rental with 100 € per year and m² is therefore 640,000 €.

Loss in value based on residential areas

The three above mentioned values „floor/ground ratio“, „rental/m²/a“ and „rental abatement“ have been entered in the edit dialog of this area - the values are therefore only valid for this individual area (local). It is also possible to enter these values on the dialog Options|Land Use for each type of general land use globally. In this case they are valid for all areas of this type. If the values have been entered globally and locally, the local values for an area dominate. Globally defined values are used for all areas of this type where no local ones exists.

Step 1 - Calculation of sound pressure levels

The calculation of levels for example 1 with a grid spacing of 1 m x 1 m and a receiver height of 4 m (see Grid Specification) leads to the result shown in the following diagram.

Result of the grid calculation with a grid spacing of 1m and a receiver height of 4m

Step 2 - Evaluation

After noise levels have been calculated on the specified grid, the evaluation in the form of a reduction in value is carried out via menu Grid|Evaluation. The example file Monetary1.cna just includes the correct expressions.

Example

Path: Examples\Immissions\Option XL\Monetary1.cna

The expression for calculating the annual reduction in rent resulting from noise is

FL*NAOK*NAGFZ*NAMIETE*NAMIND

After a click on Calculate the reduction in rent caused by the noise is shown.

Changing the number of cars (MDTD) to 10000 cars/24h, recalculating and evaluating with the described steps changes the reduction of the noise induced loss. With the same technique all possible measures like screens and barriers or reorganization of traffic flows can easily be evaluated and ranked.