Traffic NO2 formula (Traffic NO2 Overlay): Difference between revisions

Latest revision as of 09:57, 10 July 2026

The calculations follow the standard rekenmethode 1 (SRM 1).

$C j m [N O_{2}] = C a, j m [N O_{2}] + C b, j m [N O_{2}]$

where:

C j m [N O_{2}]

= the calculated annual average concentration [μg/m3],

C a, j m [N O_{2}]

= the provided annual average background-concentration (default = 0 [μg/m3]). Configured using model attribute BASE_NO2.

C b, j m [N O_{2}]

= the calculated annual average traffic contribution to NO2 concentration [μg/m3].

Contribution NO2

To compute the annual average traffic contribution to NO2, $C b, j m [N O_{2}]$ [μg/m3], the following formula from SRM1 is applied:

$C b, j m [N O_{2}] = f N O_{2} \cdot C b, j m [N O_{x}] + \frac{B \cdot C a, j m [O_{3}] \cdot C b, j m [N O_{x}] \cdot (1 - f N O_{2})}{K + C b, j m [N O_{x}] \cdot (1 - f N O_{2})}$

where:

C b, j m [N O_{x}]

= the calculated annual average traffic contribution to NOx concentration [μg/m3],

C a, j m [O_{3}]

= the provided annual average ozone concentration [μg/m3] (default = 42),

f N O_{2}

= weighted fraction direct emitted NO2 [-],

B

= parameter (default 0.6),

K

= parameter for conversion NO to NO2 (default = 100 μg/m3).

Contribution NOX

To compute the annual average traffic contribution to NOX, Cb,jm[NOX] [μg/m3], the following formula from SRM1 is applied:

$C b, j m [N O_{x}] = F_{k} \cdot E N O_{x} \cdot θ \cdot F_{b} \cdot F_{m e t e o}$

where:

F_{k}

= calibration factor [-] (default = 0.62]

E N O_{x}

= emission number NOx [μg/m/s]

θ

= dilution factor [-]

F_{b}

= tree factor (default = 1)

F_{m e t e o}

= 5/windspeed. Default value for windspeed is 5 m/s

The computation of the dilution factor, $θ$ , is split into two situations. ^[1]

For surrounding cells within a distance of 30m:

$θ = a \cdot S^{2} + b \cdot S + c$

And for cells within a distance of 30-60m (for road-type 1 only):

$θ = α \cdot S^{p}$

where:

S

= the calculation distance

a

= configurable using model attribute: ROAD1_30M_A

b

= configurable using model attribute: ROAD1_30M_B

c

= configurable using model attribute: ROAD1_30M_C

α

= configurable using model attribute: ROAD1_60M_ALPHA

p

= configurable using model attribute: ROAD1_60M_POWER

The weighted fraction of direct emitted NO2 [-] is computed as:

$f N O_{2} = \frac{E N O_{2}}{E N O_{x}}$

where:

E N O_{2}

= emission number NO2 [μg/m/s]

Tree Factor

The tree factor is calculated as follows:

$A_{t} = π \cdot \frac{d^{2}}{A_{c}}$

$F_{b} = 1 + \frac{t}{2 \cdot A_{t}}$

where:

A_{c}

= Grid cell area in square meters.

d

= Search distance of trees, currently set on 30 meters,

A_{t}

= Search area measured in amount of cells,

t

= Amount of tree cells within the search distance,

F_{b}

= Tree factor, value between 1 and 1.5.

This method for calculating the tree factor provides higher precision than the standard discrete values of 1, 1.25, or 1.5.

Emission numbers

The emission numbers (E) for both NOx and NO2 are computed as:

$E_{d r i v e} = (1.0 - j_{c}) \cdot n_{c} \cdot E_{c, d} + (1.0 - j_{v}) \cdot n_{v} \cdot E_{v, d} + (1.0 - j_{t}) \cdot n_{t} \cdot E_{t, d} + (1.0 - j_{b}) \cdot n_{b} \cdot E_{b, d}$

$E_{j a m} = j_{c} \cdot n_{c} \cdot E_{c, j} + j_{v} \cdot n_{v} \cdot E_{v, j} + j_{t} \cdot n_{t} \cdot E_{t, j} + j_{b} \cdot n_{b} \cdot E_{b, j}$

$E = (E_{d r i v e} + E_{j a m}) \cdot \frac{1000}{(24 \cdot 3600)}$

where:

E

= Calculated emission of either NOx or NO2

E_{d r i v e}

= Calculated emission of driving traffic of either NOx or NO2.

E_{j a m}

= Calculated emission of jammed traffic of either NOx or NO2.

E_{c, d}

= Calculated emission of driving cars, hourly or daily, of either NOx or NO2. Configured using Model attribute EMISSION_CAR_NOX or EMISSION_CAR_NO2 respectively.

E_{v, d}

= Calculated emission of driving vans, hourly or daily, of either NOx or NO2. Configured using Model attribute EMISSION_VAN_NOX or EMISSION_VAN_NO2 respectively.

E_{t, d}

= Calculated emission of driving trucks, hourly or daily, of either NOx or NO2. Configured using Model attribute EMISSION_TRUCK_NOX or EMISSION_TRUCK_NO2 respectively.

E_{b, d}

= Calculated emission of driving buses, hourly or daily, of either NOx or NO2. Configured using Model attribute EMISSION_BUS_NOX or EMISSION_BUS_NO2 respectively.

E_{c, j}

= Calculated emission of jammed cars, hourly or daily, of either NOx or NO2. Configured using Model attribute EMISSION_JAM_CAR_NOX or EMISSION_JAM_CAR_NO2 respectively.

E_{v, j}

= Calculated emission of jammed vans, hourly or daily, of either NOx or NO2. Configured using Model attribute EMISSION_JAM_VAN_NOX or EMISSION_JAM_VAN_NO2 respectively.

E_{t, j}

= Calculated emission of jammed trucks, hourly or daily, of either NOx or NO2. Configured using Model attribute EMISSION_JAM_TRUCK_NOX or EMISSION_JAM_TRUCK_NO2 respectively.

E_{b, j}

= Calculated emission of jammed buses, hourly or daily, of either NOx or NO2. Configured using Model attribute EMISSION_JAM_BUS_NOX or EMISSION_JAM_BUS_NO2 respectively.

n_{c}

= number of car traffic, hourly or daily value. Configured in roads using Function Value NUM_CARS or as grid prequel.

n_{v}

= number of van traffic, hourly or daily value. Configured in roads using Function Value NUM_VANS or as grid prequel.

n_{t}

= number of truck traffic, hourly or daily value. Configured in roads using Function Value NUM_TRUCKS or as grid prequel.

n_{b}

= number of bus traffic, hourly or daily value. Configured in roads using Function Value NUM_BUSES or as grid prequel.

j_{c}

= fraction of car traffic in traffic jams. Configured in roads using Function Value JAM_FACTOR_CARS.

j_{v}

= fraction of van traffic in traffic jams. Configured in roads using Function Value JAM_FACTOR_VANS.

j_{t}

= fraction of truck traffic in traffic jams. Configured in roads using Function Value JAM_FACTOR_TRUCKS.

j_{b}

= fraction of bus traffic in traffic jams. Configured in roads using Function Value JAM_FACTOR_BUSES.

Notes

If the traffic amount is defined as a single value, that value is used for all defined hours. However, if the amount is an array of values, each of the 24 indexes of that array are assumed to correspond to the hour denoted by those indexes, and as such that specific value from the array is used.
The SRM1^[2] calculation method is only applicable for urban environments.

References

↑ K. van Velze and J. Wesseling, Technische beschrijving van standaardrekenmethode 1 (SRM-1), paragraph 3.5, RIVM Briefrapport 2014-0127, https://www.rivm.nl/bibliotheek/rapporten/2014-0127.pdf
↑ SRM1 ∙ Regeling beoordeling luchtkwaliteit 2007, Bijlage I ∙ Found at: http://wetten.overheid.nl/BWBR0022817/2013-01-01#Bijlage1 ∙ (last visited: 16-02-2022)

[1] K. van Velze and J. Wesseling, Technische beschrijving van standaardrekenmethode 1 (SRM-1), paragraph 3.5, RIVM Briefrapport 2014-0127, https://www.rivm.nl/bibliotheek/rapporten/2014-0127.pdf

[ref-srm1-2] SRM1 ∙ Regeling beoordeling luchtkwaliteit 2007, Bijlage I ∙ Found at: http://wetten.overheid.nl/BWBR0022817/2013-01-01#Bijlage1 ∙ (last visited: 16-02-2022)

[1]

[2]

@@ Line 15: / Line 15: @@
 where:
 :<math> Cb,jm[NO_x]</math> = the calculated annual average traffic contribution to NOx concentration [μg/m3],
-:<math> Ca,jm[O_3]</math> = the provided annual average concentration ozon [μg/m3] (default = 42),
+:<math> Ca,jm[O_3]</math> = the provided annual average ozone concentration [μg/m3] (default = 42),
 :<math> fNO_2</math> = weighted fraction direct emitted NO2 [-],
 :<math> B</math> = parameter (default 0.6),
@@ Line 58: / Line 58: @@
 where:
-: <math> ENO_2</math> = emission number NOs [μg/m/s]
+: <math> ENO_2</math> = emission number NO2 [μg/m/s]
 ====Tree Factor====
-The tree factor is calculated as followed:
+The tree factor is calculated as follows:
 <math>A_t = \pi \cdot \frac{d^2}{A_c}</math>
@@ Line 74: / Line 74: @@
 : <math>F_b</math> = Tree factor, value between 1 and 1.5.
-Note that this way of calculating the tree factor is more detailed than the suggested calculation of the tree factor: 1, 1.25 or 1.5 and nothing in between.
+This method for calculating the tree factor provides higher precision than the standard discrete values of 1, 1.25, or 1.5.
 ====Emission numbers====
@@ Line 81: / Line 81: @@
 <math>E_{drive} = (1.0 - j_c) \cdot n_c \cdot E_{c,d} + (1.0 - j_v) \cdot n_v \cdot E_{v,d} + (1.0 - j_t) \cdot n_t \cdot E_{t,d} + (1.0 - j_b ) \cdot n_b \cdot E_{b,d}</math>
-<math>E_{jam} = j_c \cdot n_c \cdot E_{c,j} + j_v \cdot n_v \cdot E_{v,j} + j_t \cdot n_t \cdot E_{t,j} + j_b \cdot b_t \cdot E_{b,j}</math>
+<math>E_{jam} = j_c \cdot n_c \cdot E_{c,j} + j_v \cdot n_v \cdot E_{v,j} + j_t \cdot n_t \cdot E_{t,j} + j_b \cdot n_b \cdot E_{b,j}</math>
 <math>E = (E_{drive} + E_{jam} ) \cdot \frac{1000}{(24 \cdot 3600)}</math>
@@ Line 108: / Line 108: @@
 {{article end
 |notes=
-* If the traffic amount is defined as a single value, that value is used for all defined [[Hours (Traffic Density Overlay)|hours]]. However, if the amount if an [[Attribute array|array of values]], each of the 24 indexes of that array are assumed to correspond to the hour denoted by those indexes, and as such that specific value from the array is used.
+* If the traffic amount is defined as a single value, that value is used for all defined [[Hours (Traffic Density Overlay)|hours]]. However, if the amount is an [[Attribute array|array of values]], each of the 24 indexes of that array are assumed to correspond to the hour denoted by those indexes, and as such that specific value from the array is used.
 * The SRM1{{ref|srm1}} calculation method is only applicable for urban environments.
 |seealso=

Traffic NO2 formula (Traffic NO2 Overlay): Difference between revisions

Latest revision as of 09:57, 10 July 2026

Contents

Contribution NO2

Contribution NOX

Tree Factor

Emission numbers

Notes

See also

References

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