environment.sources.cnossos_road

CNOSSOS-EU road traffic source emission (Directive 2002/49/EC Annex II, 2.2).

The common noise assessment methods of the European Union describe a road as an incoherent source line of point sources 0.05 m above the pavement. Each vehicle category m radiates a directional sound power per metre of line

$$L_{W,\mathrm{eq},\mathrm{line},i,m}^{\prime }=L_{W,i,m}+10{\log }_{10}\left(\frac{Q_m}{1000v_m}\right)\text{\hspace{1em}(2.2.1)}$$

built from a rolling term (2.2.4) and a propulsion term (2.2.11), each with its own corrections for road surface, air temperature, studded tyres, road gradient and the acceleration or deceleration near a junction. This module implements the whole of 2.2 together with the coefficient database of Appendix F, in the eight octave bands from 63 Hz to 8 kHz.

Which text is implemented

Annex II was replaced by Commission Directive (EU) 2015/996, corrected by the corrigendum of OJ L 5, 10.1.2018 and amended by Commission Delegated Directive (EU) 2021/1226. The consolidated text (02002L0049) is what is implemented here:

• the equations of 2.2.2 to 2.2.6 come unchanged from 2015/996;
• the octave-band range of 2.2.1 is 63 Hz to 8 kHz as corrected in 2018 (the 2015 text said “125 Hz to 4 kHz”, which never matched Appendix F);
• Tables F-1 and F-4 are the versions replaced by 2021/1226; Tables F-2 and F-3 are unchanged since 2015/996.

Each shipped table records in its comment which instrument it comes from. The superseded 2015/996 coefficients are not shipped, but any coefficient set can be supplied through RoadEmissionCoefficients and RoadSurfaceCoefficients, which is also how a Member State substitutes its own national database (the reason Appendix F is called a database and not a table of constants).

Scope

This is the emission stage only. It produces the source power that the propagation stage consumes; splitting the source line into point sources is explicitly outside the scope of the method (2.5.3), so line_source_segment_power is offered as plain arithmetic, clearly labelled as such. The CNOSSOS propagation model itself is not ISO 9613-2; the hand-off to predicted_receiver_level mixes two methods and is a convenience, not a normative chain.

Auto-generated from the source docstrings by scripts/generate_api_docs.py (make api-docs). Do not edit by hand.

CNOSSOS_A_WEIGHTING

Constant (tuple).

CNOSSOS_A_WEIGHTING = (-26.2, -16.1, -8.6, -3.2, 0.0, 1.2, 1.0, -1.1)

JunctionType

JunctionType(*values)

Junction types k of Table F-3 for the speed-variation correction.

line_source_segment_power

line_source_segment_power(
    line_power: NDArray[np.float64] | list[float] | float,
    length: float,
) -> NDArray[np.float64]

Sound power of the point source representing a segment of source line.

$L_{W,\mathrm{segment},i}=L_{W,\mathrm{eq},\mathrm{line},i}^{\prime }+10{\log }_{10}(dL)$. This is arithmetic, not a normative rule: section 2.5.3 of Annex II states that how a line source is split into equivalent point sources “is outside the scope of the current methodology”. Only the per-metre line power is defined by the method.

Parameters

Name	Description
line_power	Per-metre line power L'_W,eq,line,i, in dB re 1 pW per metre.
length	Length dL of the segment, in m.

Returns: The segment sound power, in dB re 1 pW.

Raises

Exception	When
ValueError	If length is not positive.

ROAD_COEFFICIENTS

Constant (phonometry.environment.sources.cnossos_road.RoadEmissionCoefficients).

ROAD_OCTAVE_BANDS

Constant (tuple).

ROAD_OCTAVE_BANDS = (63.0, 125.0, 250.0, 500.0, 1000.0, 2000.0, 4000.0, 8000.0)

road_propulsion_noise

road_propulsion_noise(
    category: RoadVehicleCategory | str,
    speed: float,
    *,
    surface: RoadSurface | str | RoadSurfaceCoefficients = ...,
    gradient: float = 0.0,
    junction_distance: float | None = None,
    junction_type: JunctionType = ...,
    coefficients: RoadEmissionCoefficients = ...,
) -> NDArray[np.float64]

Propulsion-noise sound power L_WP,i,m of one vehicle (2.2.11)/(2.2.12).

$L_{W\mathrm{P},i,m}=A_{\mathrm{P},i,m}+B_{\mathrm{P},i,m}(v_m-v_{\mathrm{ref}})/v_{\mathrm{ref}}+d{L}_{W\mathrm{P},i,m}$ with dL_WP collecting the road surface (2.2.20), the road gradient (2.2.13)-(2.2.16) and the junction (2.2.18). Unlike rolling noise, the surface term is $\min \{{\alpha }_{i,m};0\}$: an absorbing surface reduces propulsion noise, a noisy one does not increase it.

Parameters

Name	Description
category	Vehicle category (Table [2.2.a]).
speed	Average speed v_m, in km/h; values below 20 km/h are raised to 20 km/h (2.2.1).
surface	Road surface, as a RoadSurface, its description or an explicit RoadSurfaceCoefficients.
gradient	Road slope s, in per cent, positive uphill in the direction of travel. For a bidirectional flow, split the flow in two and correct one half uphill and the other downhill.
junction_distance	Distance x to the junction, in m.
junction_type	Junction type k (Table F-3).
coefficients	The Appendix F database to use.

Returns: L_WP,i,m over the eight octave bands, in dB re 1 pW.

Raises

Exception	When
ValueError	If an input is invalid.

ROAD_REFERENCE_SPEED

Constant (float).

ROAD_REFERENCE_SPEED = 70.0

ROAD_REFERENCE_TEMPERATURE

Constant (float).

ROAD_REFERENCE_TEMPERATURE = 20.0

road_rolling_noise

road_rolling_noise(
    category: RoadVehicleCategory | str,
    speed: float,
    *,
    surface: RoadSurface | str | RoadSurfaceCoefficients = ...,
    temperature: float = 20.0,
    studded_fraction: float = 0.0,
    studded_months: float = 0.0,
    junction_distance: float | None = None,
    junction_type: JunctionType = ...,
    coefficients: RoadEmissionCoefficients = ...,
) -> NDArray[np.float64]

Rolling-noise sound power L_WR,i,m of one vehicle (2.2.4)/(2.2.5).

$L_{W\mathrm{R},i,m}=A_{\mathrm{R},i,m}+B_{\mathrm{R},i,m}{\log }_{10}(v_m/v_{\mathrm{ref}})+d{L}_{W\mathrm{R},i,m}$ with the correction term dL_WR collecting the road surface (2.2.19), the studded tyres (2.2.8), the junction (2.2.17) and the air temperature (2.2.10). Categories 4a and 4b have no rolling noise: their Table F-1 rows are zero, and their total power is the propulsion term alone (2.2.3).

Parameters

Name	Description
category	Vehicle category (Table [2.2.a]).
speed	Average speed v_m, in km/h; values below 20 km/h are raised to 20 km/h (2.2.1).
surface	Road surface, as a RoadSurface, its description or an explicit RoadSurfaceCoefficients.
temperature	Air temperature tau, in degrees Celsius.
studded_fraction	Q_stud,ratio of (2.2.7).
studded_months	T_s of (2.2.7), the months per year over which studded tyres are in use.
junction_distance	Distance x to the junction, in m.
junction_type	Junction type k (Table F-3).
coefficients	The Appendix F database to use.

Returns: L_WR,i,m over the eight octave bands, in dB re 1 pW.

Raises

Exception	When
ValueError	If an input is invalid.

ROAD_SOURCE_HEIGHT

Constant (float).

ROAD_SOURCE_HEIGHT = 0.05

road_source_power

road_source_power(
    traffic: RoadTraffic | list[RoadTraffic] | tuple[RoadTraffic, ...],
    *,
    surface: RoadSurface | str | RoadSurfaceCoefficients = ...,
    temperature: float = 20.0,
    gradient: float = 0.0,
    studded_months: float = 0.0,
    junction_distance: float | None = None,
    junction_type: JunctionType = ...,
    coefficients: RoadEmissionCoefficients = ...,
) -> RoadEmissionResult

Directional sound power per metre of a road source line (2.2.1).

Evaluates $L_{W,\mathrm{eq},\mathrm{line},i,m}^{\prime }=L_{W,i,m}+10{\log }_{10}(Q_m/(1000v_m))$ for every category of the traffic mix and sums the categories energetically. The flow term uses the true average speed even where the sound power itself is frozen at 20 km/h (2.2.1).

All corrections other than the per-category traffic are properties of the road segment, so they are passed once here: the surface, the air temperature, the gradient, the studded-tyre season and the junction.

Parameters

Name	Description
traffic	One RoadTraffic or a sequence of them, at most one per vehicle category.
surface	Road surface (Table F-4).
temperature	Yearly average air temperature tau, in degrees Celsius (the reference condition is 20 degC).
gradient	Road slope s, in per cent, positive uphill.
studded_months	T_s of (2.2.7), the months per year over which studded tyres are in use.
junction_distance	Distance x from the source to the nearest junction, in m; None (the default) means no junction in range.
junction_type	Junction type k (Table F-3).
coefficients	The Appendix F database to use.

Returns: A RoadEmissionResult.

Raises

Exception	When
ValueError	If the traffic is empty, repeats a category, or carries an invalid flow rate or speed.

road_surface_coefficients

road_surface_coefficients(
    surface: RoadSurface | str,
) -> RoadSurfaceCoefficients

Look up a Table F-4 row.

Parameters

Name	Description
surface	A RoadSurface member or its description string.

Returns: The RoadSurfaceCoefficients of that surface.

Raises

Exception	When
ValueError	If the surface is not tabulated in Table F-4.

road_vehicle_sound_power

road_vehicle_sound_power(
    category: RoadVehicleCategory | str,
    speed: float,
    *,
    surface: RoadSurface | str | RoadSurfaceCoefficients = ...,
    temperature: float = 20.0,
    gradient: float = 0.0,
    studded_fraction: float = 0.0,
    studded_months: float = 0.0,
    junction_distance: float | None = None,
    junction_type: JunctionType = ...,
    coefficients: RoadEmissionCoefficients = ...,
) -> NDArray[np.float64]

Total sound power L_W,i,m of a single vehicle (2.2.2)/(2.2.3).

For categories 1, 2 and 3 the rolling and propulsion terms are summed energetically (2.2.2); for the powered two-wheelers of category 4 the propulsion term is the whole of it (2.2.3).

Parameters

Name	Description
category	Vehicle category (Table [2.2.a]).
speed	Average speed v_m, in km/h.
surface	Road surface (Table F-4).
temperature	Air temperature tau, in degrees Celsius.
gradient	Road slope s, in per cent.
studded_fraction	Q_stud,ratio of (2.2.7).
studded_months	T_s of (2.2.7), in months.
junction_distance	Distance x to the junction, in m.
junction_type	Junction type k (Table F-3).
coefficients	The Appendix F database to use.

Returns: L_W,i,m over the eight octave bands, in dB re 1 pW.

Raises

Exception	When
ValueError	If an input is invalid.

RoadEmissionCoefficients

RoadEmissionCoefficients(
    rolling_a: dict[str, tuple[float, ...]],
    rolling_b: dict[str, tuple[float, ...]],
    propulsion_a: dict[str, tuple[float, ...]],
    propulsion_b: dict[str, tuple[float, ...]],
    studded_a: tuple[float, ...],
    studded_b: tuple[float, ...],
    junction_c: dict[str, tuple[tuple[float, float], tuple[float, float]]],
    temperature_k: dict[str, float],
)

Appendix F coefficient database for the road source.

Holds Tables F-1, F-2 and F-3 together with the temperature coefficients K_m of (2.2.10). The default instance, ROAD_COEFFICIENTS, carries the tables of the consolidated Directive; supplying another instance is how a Member State substitutes a national database, and how the superseded 2015/996 coefficients can be reproduced for comparison with pre-2021 studies.

Attributes

Name	Description
rolling_a	A_R,i,m per category, eight octave bands, in dB.
rolling_b	B_R,i,m per category, eight octave bands, in dB.
propulsion_a	A_P,i,m per category, eight octave bands, in dB.
propulsion_b	B_P,i,m per category, eight octave bands, in dB.
studded_a	a_i of Table F-2 (category 1 only), in dB.
studded_b	b_i of Table F-2 (category 1 only), in dB.
junction_c	(C_R, C_P) of Table F-3 per category and junction type, in dB.
temperature_k	K_m of (2.2.10), in dB per degree Celsius.

RoadEmissionResult

RoadEmissionResult(
    frequencies: NDArray[np.float64],
    categories: tuple[RoadVehicleCategory, ...],
    rolling: NDArray[np.float64],
    propulsion: NDArray[np.float64],
    vehicle_power: NDArray[np.float64],
    line_power: NDArray[np.float64],
    total_line_power: NDArray[np.float64],
    source_height: float = 0.05,
)

Directional sound power per metre of a CNOSSOS-EU road source line.

Attributes

Name	Description
frequencies	Octave-band midband frequencies, in Hz (63 Hz to 8 kHz).
categories	The vehicle categories of the modelled flows, in the order of the rows of the per-category arrays.
rolling	L_WR,i,m per category and band, in dB re 1 pW. The row of a powered two-wheeler is the zero row Table F-1 prints for it, and does not enter its sound power, which is the propulsion term alone (2.2.3).
propulsion	L_WP,i,m per category and band, in dB re 1 pW.
vehicle_power	L_W,i,m per category and band (2.2.2)/(2.2.3), in dB re 1 pW.
line_power	L'_W,eq,line,i,m per category and band (2.2.1), in dB re 1 pW per metre.
total_line_power	The energy sum of line_power over the categories, in dB re 1 pW per metre: the source strength of the line.
source_height	Height of the equivalent point source above the road surface, in m (0,05 m, fixed by 2.2.1).

RoadEmissionResult.a_weighted_line_power

property

A-weighted total line power, in dB(A) re 1 pW per metre.

Uses the octave-band weighting AWC_f,i printed in 2.5.5 as amended by (EU) 2021/1226, i.e. CNOSSOS_A_WEIGHTING.

RoadEmissionResult.plot()

RoadEmissionResult.plot(
    ax: Axes | None = None,
    *,
    language: str = 'en',
    **kwargs: Any,
) -> Axes

Plot the per-metre line power spectrum and its category breakdown.

RoadSurface

RoadSurface(*values)

Road surfaces tabulated in Table F-4 (as replaced by 2021/1226).

RoadSurfaceCoefficients

RoadSurfaceCoefficients(
    name: str,
    alpha: dict[str, tuple[float, ...]],
    beta: dict[str, float],
    speed_range: tuple[float, float] | None,
)

One row of Table F-4: the acoustic signature of a road surface.

Attributes

Name	Description
name	The surface description as printed in Table F-4.
alpha	alpha_i,m per category, eight octave bands, in dB.
beta	beta_m per category (dimensionless speed coefficient).
speed_range	(v_min, v_max) over which the row is declared valid, in km/h, or None for the reference surface, which carries no range. Carried for the reader, not enforced: Table F-4 prints these columns without attaching a consequence to them, so refusing a speed outside the range would be stricter than the method itself.

RoadTraffic

RoadTraffic(
    category: RoadVehicleCategory,
    flow_rate: float,
    speed: float,
    studded_fraction: float = 0.0,
)

The traffic of one vehicle category on a source line.

Attributes

Name	Description
category	The RoadVehicleCategory of the flow.
flow_rate	Hourly flow Q_m, in vehicles per hour.
speed	Average speed v_m, in km/h. Sound powers are frozen at 20 km/h below that speed (2.2.1); the flow term still uses the true speed.
studded_fraction	Q_stud,ratio of (2.2.7), the fraction of the light-vehicle flow fitted with studded tyres over the studded period. Ignored for every category other than category 1 (2.2.9).

RoadVehicleCategory

RoadVehicleCategory(*values)

Vehicle categories of Table [2.2.a].

Categories 1 to 4 are mandatory; the “open” category 5 has no coefficients in Appendix F and is therefore not modelled.