Traffic NO2 Overlay: Difference between revisions
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The Traffic NO2 Overlay is an [[Grid overlay|overlay]] which displays the impact of traffic air polution (in μg/m³ NO2) in different colors for the project area. These colors indicate traffic air polution of a location based on [[Traffic Flow (Overlay)|traffic flow]] and distance.<br> | |||
It becomes available for all stakeholders when added to a project. | |||
[[File:Traffic_NO2-Overlay.jpg|thumb|left|Optional Traffic NO2 (Air polution effect) overlay]] | |||
[[ | |||
<br clear=all> | <br clear=all> | ||
==Calculations== | ==Calculations== | ||
The calculations follow the standard rekenmethode 1 (SRM 1), as described on [http://wetten.overheid.nl/BWBR0022817/2013-03-22]: | The calculations follow the standard rekenmethode 1 (SRM 1), as described on [http://wetten.overheid.nl/BWBR0022817/2013-03-22]: | ||
'''Cjm = Ca,jm + Cb,jm''' | '''Cjm[NO2] = Ca,jm[NO2] + Cb,jm[NO2]''' | ||
where: | where: | ||
* Cjm = annual average concentration [μg/m3] | * Cjm[NO2] = annual average concentration [μg/m3] | ||
* Ca,jm = annual average background-concentration (default = 0 [μg/m3], can be adjusted via the overlay attributes) | * Ca,jm[NO2] = annual average background-concentration (default = 0 [μg/m3], can be adjusted via the overlay attributes) | ||
* Cb,jm = annual average traffic contribution to NO2 concentration [μg/m3] | * Cb,jm[NO2] = annual average traffic contribution to NO2 concentration [μg/m3] | ||
To compute the annual average traffic contribution to NO2, Cb,jm[NO2] [μg/m3], the following formula from SRM1 is applied: | To compute the annual average traffic contribution to NO2, Cb,jm[NO2] [μg/m3], the following formula from SRM1 is applied: | ||
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where: | where: | ||
* Cb,jm[NOX] = annual average traffic contribution to NOx concentration [μg/m3] | * Cb,jm[NOX] = annual average traffic contribution to NOx concentration [μg/m3] | ||
* Cb,jm[O3] = annual average concentration ozon [μg/m3] (default = | * Cb,jm[O3] = annual average concentration ozon [μg/m3] (default = 42) | ||
* fNO2 = weighted fraction direct emitted NO2 [-] | * fNO2 = weighted fraction direct emitted NO2 [-] | ||
* B = parameter (default 0.6) | * B = parameter (default 0.6) | ||
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* Fb = tree factor (default = XX) | * Fb = tree factor (default = XX) | ||
* Fmeteo = 5/windspeed. Default value for windspeed is 5 m/s | * Fmeteo = 5/windspeed. Default value for windspeed is 5 m/s | ||
The delution factor, θ, is computed till a distance of 30m with: | |||
'''θ = a * S^2 + b * S + c''' | |||
And from 30-60m (for road-type 1 and 4 only): | |||
'''θ = alpha * S^-0.747''' | |||
where: | |||
* S is the calculation distance | |||
* a, b, c and alpha are parameters depend on road-type: | |||
[[File:NO2_overlay_02.PNG]] | |||
The weighted fraction direct emitted NO2 [-] is computed as: | The weighted fraction direct emitted NO2 [-] is computed as: | ||
'''fNO2 = ENO2/ENOx''' | '''fNO2 = ENO2/ENOx''' | ||
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'''E = N * [(1-FS)*((1-(fm+fz+fb))*El + fm * Em + fz * Ez + fb * Eb) + FS * ((1-(fm + fz + fb)) * El,d + Fm * Em,d + fz * Ez,d+fb*Eb,d)]*1000/(24*3600)''' | '''E = N * [(1-FS)*((1-(fm+fz+fb))*El + fm * Em + fz * Ez + fb * Eb) + FS * ((1-(fm + fz + fb)) * El,d + Fm * Em,d + fz * Ez,d+fb*Eb,d)]*1000/(24*3600)''' | ||
where: | where: | ||
* N = traffic intencity [units per day] | * N = traffic intencity [units per day] | ||
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* FS = fraction congested traffic [-] | * FS = fraction congested traffic [-] | ||
* E*,d = emission factor per class (cars, vans, trucks or busses) if congested | * E*,d = emission factor per class (cars, vans, trucks or busses) if congested | ||
[[File:NO2_overlay_01.PNG]] | |||
==References== | ==References== | ||
The overlay calculations are based on Standard Calculation Method 1 (SRM1) as defined by the dutch government: [http://wetten.overheid.nl/BWBR0022817/2013-01-01#Bijlage1 wetten.overheid.nl] | The overlay calculations are based on Standard Calculation Method 1 (SRM1) as defined by the dutch government: [http://wetten.overheid.nl/BWBR0022817/2013-01-01#Bijlage1 wetten.overheid.nl] | ||
==How-to's== | |||
* [[How-to add and remove an overlay|Add and remove an overlay]] | |||
* [[How-to edit an overlay legend|Edit an overlay legend]] | |||
{{Template:Overlay nav}} |
Revision as of 15:05, 1 July 2019
The Traffic NO2 Overlay is an overlay which displays the impact of traffic air polution (in μg/m³ NO2) in different colors for the project area. These colors indicate traffic air polution of a location based on traffic flow and distance.
It becomes available for all stakeholders when added to a project.
Calculations
The calculations follow the standard rekenmethode 1 (SRM 1), as described on [1]:
Cjm[NO2] = Ca,jm[NO2] + Cb,jm[NO2]
where:
- Cjm[NO2] = annual average concentration [μg/m3]
- Ca,jm[NO2] = annual average background-concentration (default = 0 [μg/m3], can be adjusted via the overlay attributes)
- Cb,jm[NO2] = annual average traffic contribution to NO2 concentration [μg/m3]
To compute the annual average traffic contribution to NO2, Cb,jm[NO2] [μg/m3], the following formula from SRM1 is applied:
Cb,jm[NO2]= fNO2 * Cb,jm[NOx] + (B*Ca,jm[O3]*Cb,jm[NOx]*(1-fNO2))/(Cb,jm[NOx]*(1-Fno2)+K)
where:
- Cb,jm[NOX] = annual average traffic contribution to NOx concentration [μg/m3]
- Cb,jm[O3] = annual average concentration ozon [μg/m3] (default = 42)
- fNO2 = weighted fraction direct emitted NO2 [-]
- B = parameter (default 0.6)
- K = parameter for conversion NO to NO2 (default = 100 μg/m3)
To compute the annual average traffic contribution to NOX, Cb,jm[NOX] [μg/m3], the following formula from SRM1 is applied:
Cb,jm[NOx] = Fk * ENOx * θ * Fb * Fmeteo
where:
- Fk = calibration factor [-] (default = 0.62]
- ENOx = emission number NOx [μg/m/s]
- θ = delution factor [-]
- Fb = tree factor (default = XX)
- Fmeteo = 5/windspeed. Default value for windspeed is 5 m/s
The delution factor, θ, is computed till a distance of 30m with:
θ = a * S^2 + b * S + c
And from 30-60m (for road-type 1 and 4 only):
θ = alpha * S^-0.747
where:
- S is the calculation distance
- a, b, c and alpha are parameters depend on road-type:
The weighted fraction direct emitted NO2 [-] is computed as:
fNO2 = ENO2/ENOx
where:
- ENO2 = emission number NOs [μg/m/s]
The emission numbers (E) for both NOx and NO2 are computed as:
E = N * [(1-FS)*((1-(fm+fz+fb))*El + fm * Em + fz * Ez + fb * Eb) + FS * ((1-(fm + fz + fb)) * El,d + Fm * Em,d + fz * Ez,d+fb*Eb,d)]*1000/(24*3600)
where:
- N = traffic intencity [units per day]
- fm = fraction vans [-]
- fz = fraction trucks [-]
- fb = fraction busses [-]
- El = emission value cars [g/km]
- Em = emission value vans [g/km]
- Ez = emission value trucks [g/km]
- Eb = emission value busses [g/km]
- FS = fraction congested traffic [-]
- E*,d = emission factor per class (cars, vans, trucks or busses) if congested
References
The overlay calculations are based on Standard Calculation Method 1 (SRM1) as defined by the dutch government: wetten.overheid.nl
How-to's