Road Noise Module

What does this module do?

What Standards are supported?

bullet RLS 90(Germany)
bullet RLS 90 - strict rules(Germany)
bullet DIN 18005 Strasse 1987-05(Germany)
bullet VBUS(Germany)
bullet VRSS: 1975 (Germany)
bullet Calculation of Road Traffic Noise (UK)
bullet Calculation of Road Traffic Noise (Australia, NSW)
bullet Swizerland EMPA
bullet RVS 3.02/4.02 (Austria)
bullet Statens Planverk report no. 48: 1980
bullet Road Traffic Noise - Nordic Prediction Method; 1996
bullet Nord 2000 Road
bullet ASJ RTN-Model B 1998 (Japan)
bullet ASJ RTN-Model B 2003 (Japan)
bullet ASJ RTN-Model B 2008 (Japan)
bullet NMPB - Routes - 96  (France, Europe)
bullet NMPB - Routes - 2008 (France, Europe)
bullet ENEA (Italy)
bullet FHWA, 1978 (USA)
bullet Traffic Noise Model - FHWA 1998 (USA)
bullet Russian Road
bullet ODM 218. 013-2011; Russia
bullet HJ2 4-2009 Road; China
 

The Road Noise Module

Road noise is the most widespread noise problem- world wide! The SoundPLAN road noise module is split into 2 sections, first the emissions of the line source are evaluated and assigned to the road source objects in the Geo-Database. In a second step noise levels are calculated for stand alone receivers or as part of the Grid Noise Map, Facade Noise Map, Cross-Sectional Noise Map or the Meshed Noise Map.

To mitigate the noise, speed restrictions on the road, quiet road surface, harmonization of the traffic flow, concentration of the major flow on arterial roads and noise protection walls are available. The optimization of berms and noise protection walls is described in the module WallDesign.

You can select any of the standards on the left for your work but must understand that for road noise (and also for railway noise) the emissions are standard specific and it is not possible to enter the road for the German RLS 90 and then calculate the noise levels in accordance to the British CoRTN. Emission and propagation must be defined for the same standard!

Most of the calculation standards have chosen to assess the noise levels for the Leq, CoRTN is the exception here with the L10 (for the END there is a conversion to Leq). For Leq based calculations it is possible create comprehensive answers with road noise and the noise from railway and industry.

Emission Calculation

From the number of vehicles, the speed and the road surface, the GeoDatabase calculates the emission of the road. This emission is assigned to the coordinate where it was defined and is valid until a new definition replaces it. The factors and formulas for the emission parameters are standard dependant and as we have well over 20 standards,  we refer here to your copy of the standard. What you find there is also part of the emission calculation. Some standards have extra provisions for traffic lights while others have provisions for the change in vehicle speed for roads up the hill.

The emission can be for 24 hours of the day or for the 3 time slots day/evening/night or for day/night. Some "emissions" of roads are the sound power Lw, for other standards the emission (or basic noise level) is the sound pressure in a reference distance (10m, 15m, 25m) depending on the standard.

Roads with emission are saved by the GeoDatabase and processed by the calculation core.

Import Road Data

With the DXF import interface you can import the coordinates of a road but not the attributes. On the left is a sample import of many objects organized layer by layer. Select the layer to import, import the data into a temporary Geo-File and then convert the data into the object (here roads) that you want the data to represent.

The Shape file interface allows to import attributes in addition to the coordinates. When importing such a file for the first time the program will show the attributes in the Shape File and all possible attributes for this object in SoundPLAN and lets you choose what needs to go where. After importing the data for the first time, the program already knows the correspondence and the import is faster. (See Shape File Interface)

 

One Road, many data sources

Importing a road from an external source does not mean that with one import the optimal results are achieved in one sitting. The road that had all extra parameters such as road width, road surface and the traffic related parameters was imported from an ArcView Shape File. The spacing of the coordinates resulted in a relatively jagged road that actually might cause problems being at some coordinates too close to buildings.

Fortunately we were able to get better alignment data from another source but these data only had the coordinates but no attributes. To rectify the problem, we divided the existing road into smaller segments, invoked the function "adapt road (or railway" to get the correct shape of the road and then filtered out excessive coordinates.

The SoundPLAN Geo-Database is a toolbox that helps the engineer load, merge and correct model data into a consistent, high quality noise model.

 

One Road, many Definitions

A single road can be many kilometers long with the traffic volume changing at many intersections and many changes in road width, vehicle speed, road surface, incline etc.

In SoundPLAN any of these parameters can change at any coordinate and still maintain the integrity of the road. This is an important feature in SoundPLAN as often we need to produce the answers of our noise simulations with contributions road by road. Often this is a question which part of the government (local, state, federal) is paying for improvements to the noise situation. In SoundPLAN you enter one road and you get one contribution, there is no need to later on use a spreadsheet to add the contributions just because the road has some places where the width or road surface changed.

On the left a single road can be seen with the double coordinate rings (1) where one or more of the road attributed changed. The single coordinates (2) has no changes in attributes.

 

Bridges

Bridges are structures where the noise can pass underneath. The noise from traffic on the bridge itself is shielded by the edge of the bridge surface or the  solid barrier on the side. These parameters are assigned to the road itself.

For big noise maps it can be tedious to find the bridges, so SoundPLAN has implemented an algorithm to automatically detect the bridges from the terrain information around it. Mark the roads you want to detect bridges on and start Geo-Tools/more elevation tools/bridge detection you can enter into a search to find bridges = anormalities in the terrain. The height of the bridge edge then is a bit of a manual adjustment.

 

Set the Road on Top of the Terrain

Usually SoundPLAN tries to reduce the amount of data loaded for a DGM. When importing aerial photogrammetric data the noise model can afford to have a tolerance of 0.5 in height variation. When importing and triangulating the elevation spot heights, the DGM may contain triangles that "reach" across the road. These triangles then will pass the wrong elevation to the coordinates of the road. 

The better solution is to geographically restrict the import to import elevations only for the road surface without filtering them, triangulate the data into a temporary DGM and then set the roads on top of this triangulation. On the left you see the imported spot elevations for the road only, in the lower picture there is a enlargement with the road itself loaded.

 

Modeling the Terrain to the Road

Often a noise study is required for a new road. The planners want to know if noise protection is required and they have the coordinates of the road but not the adjustments that need to be made to the terrain.

 

 

 

 

 

 

 

 

 

If the terrain is viewed with the elevations from the Digital Ground Model color coded it is clearly visible that the road in part is under the terrain and in other parts is floating on top of the terrain.

If the elevation supply to this model was done using elevation lines, the fix is fast.

Select the Geo-Tools/Create Embankments to intersect the terrain and the road and create the embankment lines you see in the lower picture.

Noise from Road Tunnels

On the left you see the same situation as was modeled with the terrain but instead of a deep cutting, a tunnel was planned. Tunnels acoustically cannot be ignored, they need to be modeled in a special way.

Unlike regular road noise where the emission is close to the road surface, noise from tunnels is emitted over the entire moth of the tunnel. Depending on the absorptive characteristic of the tunnel walls, the frequencies shift to the lower frequencies, and the noise is emitted with a directivity. All these factors are included in the SoundPLAN object for tunnels.

The middle picture on the left depicts the regions around the tunnel mouth where the noise levels will be higher than from a regular road (SoundPLAN difference map), below is a typical directivity plot from the tunnel mouth.

See also the ppt for noise from tunnels

Time History

Traffic is never constant, there are morning, noon and evening rush hour and at night very few vehicles. These parameters depend on the road type, location, country etc.

In SoundPLAN you can define the distribution of vehicles over the 24h of the day so that for every hour the noise emissions are known. On the left this was done for the Nord 2000 but template type vehicle numbers can be generated for all other standards. As these are templates, the real numbers are then expanded by taking the hourly percentage values and the average daily traffic volume to generate the vehicle numbers per hour.

Reflections Calculate or Estimate

In urban streets especially in areas where high rises are involved, the noise levels are much higher than in the free field. The noise is bouncing from building to building, something that can be replicated in SoundPLAN by setting the number of calculated consecutive reflections to a fairly high number.

As reflections are time consuming (the increase in calculation time is roughly going up with the second power of the number of reflections allowed), a calculation with 20 reflections in a big city for an END noise map is not feasible.

The alternative is an automatic partitioning of the roads into sections with nearly constant conditions of building height and spacing and the evaluation of the addition for multiple reflections from some equations defined in the German RLS 90. The multiple reflection addition is then added to the emission of the road.

The direct transmission and the first order of reflections are calculated, the increase of the noise levels due to the multiple reflections is added into the road emissions.

Noise barriers of many shapes

Noise barriers do not have to be vertical structures, they can have different forms. In SoundPLAN you can define the angle between the sections and how many there are, the barrier below has first a vertical element of 4 m, then 5 of 1 m with 15 degrees between them and then the flat part with 7 meters.

Complex Geometry: Floating Buildings

Now buildings and industrial buildings can act like floating screens with noise passing underneath. The requirement is to ensure the building has this attribute enabled: "Building floats above ground." This also means you can now model stacked buildings with Facade Noise Maps - even for the part with a smaller footprint, as you can see to the left.

 

Results Where? What?

Roads can be found as part of Single Point Receiver calculations (see the Result Tables) or part of a noise map in the graphics (see Grid Noise Map, Facade Noise Map or Meshed Map)

Copyright 2014 SoundPLAN international LLC, Shelton, WA 98584, USA