Matching noise emission from French medium-heavy vehicles and CNOSSOS
models∗Marie-Agnès PALLAS(1) , Adrien LE BELLEC(1) , David ECOTIERE(2)(1) Univ Lyon, IFSTTAR, CEREMA, UMRAE, F-69675, Lyon, France(2) CEREMA, IFSTTAR, UMRAE, F-67035, Strasbourg, France

Abstract
The CNOSSOS-EU prediction method, mandatory since 2019 for noise mapping in compliance with the European Noise Directive, speciﬁes the road vehicle noise equations to be used per vehicle category. French noise
emission data differ signiﬁcantly from the European model and a national decree was published in June 2018
to provide CNOSSOS corrective coefﬁcients in accordance with the national NMPB2008 model. However, theEuropean semi-heavy vehicle category is non-existent in both French emission model and databases, thus lacking to support the proposed coefﬁcients at this stage. To provide missing information, detailed measurements
under controlled conditions have been performed on a sample group of semi-heavy vehicles. The contributionof propulsion noise and rolling noise were separated and average emission equations were proposed by subcategory. For two trafﬁc composition scenarios, mainly differing by the ratio of public transport vehicles, anoise emission model has been proposed to represent an average medium-heavy vehicle. The paper presents
the approach and the models obtained. The representativeness of the European prediction model in its initial
version published in 2015, in its French adaptation of June 2018 and in two further versions, is considered forboth scenarios. Comparisons of frequency characteristics are emphasized.
Keywords: noise emission, trucks, CNOSSOS

1

INTRODUCTION

European Directive 2002/49/EC of 25 June 2002 on the evaluation and management of the environmental noise[1] requires Member States to produce noise maps assessing exposure to environmental noise, particularly inlarge urban areas and around major roads. It was completed in May 2015 by Directive 2015/996 [2] specifying
a common assessment method for all Member States, CNOSSOS-EU, then marginally corrected at the beginningof 2018 [3]. This new method for noise mapping came into effect at the beginning of 2019. The adaptation of
the model to the French road network and vehicle ﬂeet was published in June 2018 [4].
The vehicle category 2 of CNOSSOS-EU refers to medium-heavy vehicles, which are not differentiated among
heavy vehicles in the classiﬁcation used by the French noise prediction method NMPB2008 [5]. Their actual noise emission on French roads is not documented. However, statistical pass-by measurements carried out
on several roads pointed out discrepancies with medium-heavy vehicle noise prediction by CNOSSOS-EU [6].
Based on a series of controlled pass-by measurements involving a sample of medium-heavy vehicles driving atconstant speed, average noise emission models have been determined for two scenario options of trafﬁc composition of category 2, differing by the proportion of public transportation vehicles, with an effect on the propulsion noise contribution [7]. Then, the relevance of CNOSSOS-EU for predicting noise emission of a French
average medium-heavy vehicle is raised. Several versions of CNOSSOS should be considered: CNOSSOS-EU
currently in effect according to 2015 Directive, CNOSSOS-FR corresponding to its adaptation to French road
network, an updated version of CNOSSOS-EU elaborated in 2018 after the detection of issues in the original
version [8]. For further illustration, to this list is added the Dutch version recommended for noise mapping in
the Netherlands from 2019 onwards [9].
∗ marie-agnes.pallas@ifsttar.fr

3622

After a presentation of these CNOSSOS versions in section 2, the procedure that established the noise emissionof a French average medium-heavy vehicle within the two scenarios is recalled (section 3). A confrontationof these average category 2 vehicles with the four versions of CNOSSOS is discussed, both considering global
A-weighted levels and frequency spectra, focusing on urban speed conditions where propulsion noise in predominant (section 4).

2

NOISE EMISSION MODELSThe method CNOSSOS-EU published in 2015 [2, 3] is currently the reference European version. It was usedas the basis for the French transposition and adapted to French trafﬁc and road network speciﬁcities throughcorrective coefﬁcients. An underlying mismatch of the European road emission model has recently been raised
and an updated version of the reference CNOSSOS-EU version is being examined. Simultaneously, other Member States published their own transposition; the implementation in effect in the Netherlands is also consideredhere. These various versions are summerised in this section.
2.1 Reference CNOSSOS-EU method
The CNOSSOS-EU road noise emission model considers four vehicle categories, according to their mass andaxle number [2]. Category 2 concerns medium-heavy vehicles, with a mass larger than 3.5 tons, two axles andtwin tyres on the rear axle. It includes a wide variety of vehicles with various uses, bodies and equipment –i.e. delivery-, dump- and garbage trucks, tankers, buses and coaches – as long as they have only two axles.
Any vehicle is modelled by a single omnidirectional point source, located 0.05 m above ground. Its acoustic
power speciﬁed in the octave bands [63 Hz - 8 kHz] under reference conditions (constant speed, ﬂat and dryroad, air temperature of 20◦ C and a virtual road surface corresponding to an average of DAC 0/11 and SMA
0/11). If conditions deviate from these, correction coefﬁcients shall be used.
In each octave band i, the total power radiated by the point source LW T,i is composed of a propulsion noise
component LW P,i and a rolling noise component LW R,i , depending on vehicle speed v:
LW T,i (v) = LW R,i (v) ⊕ LW P,i (v)where the operator ⊕ stands for the energetic sum of both components and:v
LW R,i (v) = AR,i + BR,i logvre fv − vre f
LW P,i (v) = AP,i + BP,i
vre f

(1)

(2)
(3)

The coefﬁcients AR,i , BR,i , AP,i and BP,i are given in Table F-1 of the Directive [2], and vre f = 70 km/h.
Corrective terms ΔLW R,road,i and ΔLW P,road,i are available for rolling noise and propulsion noise respectively, so
as to take into account the effect of the road surface on vehicle noise emission:
 
v
(4)
ΔLW R,road,i (v) = αi + β log
v0(5)
ΔLW P,road,i (v) = min{αi ; 0}
the latter being designed to account for the effect of absorbing surfaces on propulsion noise. Values of thecoefﬁcients αi and β are given in Table F-4 of the Directive for each vehicle category on various Dutch roadsurfaces. For each road pavement, it should be noticed that the corrective coefﬁcients for medium-heavy vehicles
are always identical to those of the heavy vehicles, reﬂecting a similar noise level impact of a road surfacechange for both categories.
The corrective coefﬁcients αi and β are the means of action to adapt the model to the French road surfaces.

3623

2.2 French adaptation CNOSSOS-FR
The French prediction method NMPB2008 was implemented as a transitional method for the previous rounds ofstrategic noise map production, pending the availability of the common European method. The propagation partof CNOSSOS-EU is quite similar to the French approach, but the respective road noise emission models differ
with regard to the vehicle classiﬁcation and to the sound power levels, among other things. Indeed, NMPB2008
identiﬁes only two types of vehicles: light vehicles and heavy vehicles [5], the former matching with CNOSSOS
category 1 and the latter with category 3. In addition, it clusters and ranks road surfaces into three groups, R1,
R2 and R3, from the quietest to the noisiest, each one split in drainage or non-drainage surfaces. NMPB2008
was built on a wide set of national measurements and is considered as representative of the vehicle ﬂeet drivingon the French road network.
An adaptation of CNOSSOS-EU to the French context has been proposed by calculating correction coefﬁcients
αi and β that best match CNOSSOS to the NMPB2008 model, respectively for vehicle categories 1 and 3
and each road surface cluster [10]. For the undocumented French category 2, the adaptation has taken the same
approach as Table F-4 of CNOSSOS-EU by replicating the correction coefﬁcients of category 3 [4]. This French
adaptation is named CNOSSOS-FR in this paper.
It should be noted that, in road and vehicle conditions similar to the reference conditions of CNOSSOS-EU,
the use of uncorrected CNOSSOS-EU greatly undervalues French noise emission levels. This results in the
production of quite signiﬁcant correction terms, even for low-noise surfaces.
2.3 Corrected version of CNOSSOS-EU
Some errors have recently been identiﬁed in the derivation of the sound power coefﬁcients given in Table
F-1 of CNOSSOS-EU, partly resulting from a mismatch between the respective propagation models of Harmonoise/IMAGINE and of CNOSSOS-EU [8]. Among other issues, the need for an update of Table F-1 has
been pointed out and discussed in 2018 within a European working group [11]. This affects the coefﬁcient
A for both the propulsion and rolling noise components, without changing the B coefﬁcients and therefore thecomponent dependence on speed [8]. For vehicle categories 2 and 3, upgraded coefﬁcients provide higher overall sound power levels by 2 to more than 3 dB(A) depending on speed. This modiﬁed CNOSSOS version isnamed CNOSSOS-2018 in the present paper.
2.4 Dutch adaptation CNOSSOS-NL
The adaptation of CNOSSOS-EU for noise mapping implementation in the Netherlands includes own soundpower coefﬁcients for the respective propulsion and rolling noise components, designed in accordance with thegeneral equations (1)-(3) and the reference conditions speciﬁed in the European directive. A speciﬁc set of
coefﬁcients AR , BR , AP and BP is given in table 2.2.b of the Dutch method [9], providing own speed-dependent
sound power levels for the different vehicle categories.
2.5 Comparison of the models for vehicle category 2
By likening the reference surface of CNOSSOS-EU to the non-drainage group R2 of the French classiﬁcation,
the previous models are compared for vehicle category 2, namely:• CNOSSOS-EU, CNOSSOS-2018 and CNOSSOS-NL in reference conditions• CNOSSOS-FR for a non drainage R2 surface
The quantities represented are A-weighted sound power levels (LWA ).
For a dense road surface, CNOSSOS-EU and CNOSSOS-FR noise emission models have identical propulsion
noise components and differ by their rolling noise contribution. CNOSSOS-2018 is different from the preceding
ones both in the propulsion and the rolling noise components, as well as CNOSSOS-NL. CNOSSOS-EU gives
the lowest global propulsion and rolling noise contributions, while CNOSSOS-FR provides the highest rolling3624

noise contribution with the steepest speed increase. CNOSSOS-NL gives the highest propulsion noise prediction.
The total noise shows variable differences between models over the speed range, according to the predominanceof the propulsion noise and the rolling noise contributions in the octave bands (Figure 1).
120

L WA (dBA)

115

Global levels - Total noise - Cat. 2
CNOSSOS-EU ref. conditions
CNOSSOS-FR R2 non drainage
CNOSSOS-2018 ref. conditions
CNOSSOS-NL ref. conditions

110

105

100

95
20

30

40
50
speed (km/h)

60

70

90

110

Figure 1. Comparison of the overall noise emission models for vehicle category 2, A-weighted global soundpower levels

3

NOISE EMISSION OF AN AVERAGE MEDIUM-HEAVY VEHICLE

To ﬁll the gap in knowledge about the actual noise emission of medium-heavy vehicles on French road network,
an experimental study has been conducted to determine a representative noise emission equation of this vehicle
category. It relies on controlled pass-by noise measurements carried out on a set of vehicles, used to build amodel for the noise emission from an average medium-heavy vehicle in two trafﬁc mix scenarios. This section
summarises the procedure followed to obtain the propulsion and rolling noise contributions of one vehicle, thenthe determination of the average model in each of the two trafﬁc scenarios. More details are available in [7].
3.1 Analysis of a controlled vehicle
All the controlled medium-heavy vehicles have been measured under very close conditions and similarly analysed. For each of them, the gear ratios and the axle ratio were known. The pass-by measurement procedure
was based on standard NF S 31119-2 [13], similar to ISO 11819-1 [12] but for controlled vehicles. Infraredcells provided information on the vehicle speed. Constant speed pass-bys were carried out in 5 or 10 km/h
steps from 15 to 90 km/h. As far as possible two different engaged gears were tested for each speed setpoint,
the adapted gear (most natural gear for the speed) and the inferior gear (one gear lower, thus involving a largerrpm). Knowledge of the powertrain mechanical characteristics made it possible to calculate the engine rpm fromthe speed. The acoustic quantity considered is the maximum A-weighted noise pressure level on the microphone
at roadside.
In accordance with CNOSSOS prediction model the analysis has been carried out in octave bands from 63 Hz to8000 Hz. The vehicle noise emission equation in each octave band i was determined by optimising parametersof a noise level model LAmax,i,mod , using a least squares criterium between the set of measured levels LAmax,i,meas
and the model LAmax,i,mod :2min LAmax,i,meas − LAmax,i,mod (6)
In this model, given by Equation (7), the total noise is the sum of a propulsion noise component depending on3625

engine speed (Equation 8) and of a rolling noise component depending on vehicle speed (Equation 9).
LAmax,i,mod (N, v) = LA,prop,i (N) ⊕ LA,roll,i (v)NLA,prop,i (N) = L0,A,prop,i + αA,prop,i log
Nre f


v
LA,roll,i (v) = L0,A,roll,i + αA,roll,i log
vre f

(7)
(8)
(9)

where Nre f and vre f are respectively the reference engine speed and the driving speed, and the operator ⊕stands for energetic summation.
Thereafter, considering the commonly used adapted gear driving conditions, a one-to-one relationship links
vehicle speed to engine rpm Nadapt (v). Thus, the noise emission equation of the vehicle at adapted gear depends
on the sole variable v, using the previously optimised coefﬁcients L0,A,prop,i , αA,prop,i , L0,A,roll,i and αA,roll,i(Equation 10). In practice, the propulsion noise component has discontinuities – and consequently the overallnoise – at speeds where a gearbox shift occurs since implying large engine rpm changes.



 

Nadapt (v)v
LAmax,adapt,i (v) = L0,A,prop,i + αA,prop,i log⊕ L0,A,roll,i + αA,roll,i log
(10)
Nre f
vre f
The same operation has been performed with each vehicle tested. All vehicles had an internal combustion
engine and were tested at one of two sites with a DAC 0/10 road surface. The propulsion and the rolling noise
components of each vehicle in adapted gear have been used to determine average contributions from the set ofvehicles.
3.2 Vehicle subcategories and trafﬁc scenarios
The total number of vehicles tested is still limited, since seven vehicles could be assessed in depth. Several
types of medium-heavy vehicles have been investigated, with various functions, makes, models and tyre types
and wears. They have been grouped in subcategories, designated with the generic names van truck (intended
for the delivery of packaged goods), dump truck (used for the transport of bulk materials for public works) andbus [7]. This classiﬁcation was motivated by noticing some homogeneity within a subcategory but signiﬁcantdifferences between them. A mean emission law has been determined in each subcategory by energeticallyaveraging propulsion noise components on the one hand and rolling noise components on the other hand peroctave band, on the shared speed test range. Concerning propulsion noise, averaging tends to smooth out thevehicle-speciﬁc discontinuities spread over the speed range. Propulsion noise differences provide an obvious
subcategory ranking dump trucks > van trucks > bus and may exceed 8 dB(A) between the average dump truck
and the bus. Van trucks approximately lie at mid-range within this extent [7].
The determination of the noise emission model representative of French vehicles of category 2 results fromassumptions on the trafﬁc mix, weighting the noise emitted by each subcategory. Two trafﬁc composition scenarios of category 2 have been retained, deﬁned by a proportion nv of van trucks (including refrigerator trucks),
a proportion nd of dump trucks (including tank-, ﬂatbed-, container-, refuse trucks) and a proportion nb of buses(urban buses and coaches), with nv + nd + nb = 1 (Table 1). They result from punctual subcategory counting
performed at four varied locations and differ mainly by their ratio of public transport vehicles [7]. Critical forthe average propulsion noise component, the trafﬁc mix has a negligible effect on the average rolling noise
component.
3.3 Vehicle noise emission models
For each trafﬁc mix scenario, the next step consists in calculating the optimal coefﬁcients ÂP,i and B̂P,i (resp.
ÂR,i and B̂R,i ) of an emission model given by the CNOSSOS equation (3) (resp. equation (2)), ﬁtted to theprevious average propulsion (resp. rolling) noise component.

3626

Table 1. Proportion of vehicles in each subcategory of the trafﬁc mix
Scenario
Low public transport ratio
High public transport ratio

nv
61 %
27 %

nd
34 %
20 %

nb
5 %
53 %

The noise emission model associated with each scenario, extrapolated up to 110 km/h, is drawn in Figure 2(left). Since differences between scenarios affect the propulsion noise only, the overall noise differs acousticallyat low speed but not at high speed. In any case, the propulsion noise dominates up to more or less 50 km/h,
then rolling noise prevails. This seems reasonable at the light of road noise knowledge. On the contrary,
CNOSSOS-EU global rolling noise reaches propulsion noise contribution at about 100 km/h only and rollingnoise is of the same order of magnitude as propulsion noise at the best, even at the frequencies where its
contribution is known to be strong.
5

120

110

4
3

L WA (dB(A))

L WA (dB(A))

115

propulsion, low bus ratio
propulsion, high bus ratio
rolling
total, low bus ratio
total, high bus ratio

105
100

1
0

95
90
20

2

propulsion noise
total noise

-1
30

40
50
Speed (km/h)

70

90

110

-2
20

30

40
50
Speed (km/h)

70

90

110

Figure 2. Noise emission models for an average vehicle of category 2 in two trafﬁc mix scenarios. Left:
A-weighted global sound power levels. Right: noise level difference between the scenarios.
The propulsion noise difference between the scenarios is almost constant over the whole speed range, equal to
1.6 dB(A) in global levels. This gives a varying difference on total noise, from 1.6 dB(A) at low speed anddecreasing to become insigniﬁcant at high speed. It remains over 1 dB(A) up to 40 km/h (Figure 2, right). The
scenario issue therefore concerns mainly urban areas and city centres. The rolling noise component is typical of
the two DAC 0/10 surfaces of the test tracks. A statistical approach covering R2 road surfaces is still needed
to reﬁne the relevant rolling noise model for class R2.

4

CONFRONTATION OF THE AVERAGE MEDIUM-HEAVY VEHICLE TO CNOSSOSNOISE EMISSION

Considering the road surface of the test sites, both scenarios are compared to CNOSSOS-EU, CNOSSOS-2018
and CNOSSOS-NL in reference conditions, and to CNOSSOS-FR with the road surface group R2 non-drainage,
regarding global noise levels (Figure 3 left). A focus is done on the key contribution of the propulsion noise at
low speed through the noise spectra at 20 km/h (Figure 3 right). The relevance of the CNOSSOS versions withthe average models associated to the two scenarios depends both on traﬁc mix and speed.
CNOSSOS-EU is well adapted to the scenario with a high public transport ratio up to 40 km/h but undervalues
the other scenario by 1 to 1.5 dB(A). In this speed range, this relies mainly on the propulsion noise contribution. Its propulsion noise spectrum at low speed is relevant over the dominant frequency range 500-4000 Hz.

3627

Differences occur mainly at both ends of the spectrum, either overpredicting or underestimating the noise emitted by the average vehicle in these secondary frequency bands. In both trafﬁc mix scenarios, CNOSSOS-EU
in reference conditions undervalues the vehicle noise emission at high speeds, up to 4 dB(A) at 110 km/h androad corrective terms are required for prediction improvement.
CNOSSOS-2018, the corrected version proposed in the European working group, overestimates the overall noise
emission, up to 1.6 dB(A) at low and medium speeds with a low public transport ratio and up to 2.8 dB(A)if this ratio is high. In the former case, the overestimation comes from most of the frequency range. The
propulsion noise level increase with speed is too rapid with respect to the average experimental result. Thus,
if considering the basic ﬂexibility of CNOSSOS approach, its adaptation to the French average vehicle of category 2 would be tricky in this case since corrective terms provide no mean of reducing propulsion noise level
contribution, then the overall noise level.
The comments made for CNOSSOS-2018 are still heightened with the Dutch model CNOSSOS-NL and it seems
that the average medium-heavy vehicles differ signiﬁcantly in both countries, in particular regarding the higher
propulsion noise contribution.
CNOSSOS-FR is now recommended for new noise mapping rounds in France. Its ability to correctly ﬁgure
the noise situation is essential. Its propulsion noise component is identical to the one of CNOSSOS-EU andthe above comments on CNOSSOS-EU propulsion apply here. On the present experimental test basis andconsidering the overall noise for the road category R2 non-drainage, it happens to be an acceptable compromisefor both scenarios prediction in urban conditions. In a typical urban scenario with a high public transport ratio,
overestimation is lower than 1 dB(A) at 20-30 km/h and smaller than 2 dB(A) over the whole speed range. If
the public transport ratio is low the noise prediction error remains within ±1 dB(A) up to 50 km/h and does
not exceed 1.3 dB(A) at medium and higher speeds.

120

PROPULSION NOISE
Speed 20 km/h

110

low bus ratio
high bus ratio
CNOSSOS-EU & CNOSSOS-FR
CNOSSOS-2018
CNOSSOS-NL

105

115

L WA (dB(A))

LWA (dB(A))

100

110
105
total, low bus ratio
total, high bus ratio
CNOSSOS-EU
CNOSSOS-2018
CNOSSOS-FR
CNOSSOS-NL

100
95
90
20

30

40

50

Speed (km/h)

70

90

95
90
85
80
75

110

70
63

125

250

500 1000 2000
Frequency (Hz)

4000

8000

Figure 3. Comparison of the CNOSSOS noise emission models to the average medium-heavy vehicle of the two
scenarios. Left: overall A-weighted global sound power levels. Right: sound power spectrum of the propulsion
noise contribution at 20 km/h

5CONCLUSIONSThe noise prediction method CNOSSOS-EU allows the production of road strategic noise maps based on noise
emission models per vehicle category. The medium-heavy vehicles are not classiﬁed in the French noise
database, which was an issue for adapting the European method to the French context. Thus, based on a series3628

of measurements carried out on controlled vehicles at bass-by and on two scenarios of medium-heavy trafﬁcmix, average noise emission in accordance with the CNOSSOS model has been set for each case. This result
has been compared with the noise emission prediction of CNOSSOS. In the present context of the European
method likely to be updated, several versions of CNOSSOS have been considered, including the one currently
in effect in France. It turns out that the latter gives noise prediction levels with an error not exceeding 2 dB(A),even less according to the scenario. However, a future CNOSSOS version involving a higher propulsion noise
contribution would make an adaptation through the sole correction on rolling noise inappropriate.

ACKNOWLEDGEMENTS
This project was funded by the French Ministry for an Ecological and Inclusive Transition. It was also supported by the LABEX CeLyA (ANR-10-LABX-0060) of Université de Lyon, within the program « Investissements d’Avenir » (ANR-11-IDEX-0007) operated by the French National Research Agency (ANR). The authors
thank the entities who made some vehicles available.

REFERENCES[1] Directive 2002/49/EC of the European Parliament and of the Council of 25 June 2002 relating to the assessment and management of environmental noise, 2002.
[2] Commission Directive (EU) 2015/996 of 19 May 2015 establishing common noise assessment methods according to Directive 2002/49/EC of the European Parliament and of the Council, 2015.
[3] Corrigendum to Commission Directive (EU) 2015/996 of 19 May 2015 establishing common noise assessment methods according to Directive 2002/49/EC of the European Parliament and of the Council, 2018.
[4] Arrêté du 01/06/2018 modiﬁant l’arrêté du 4 avril 2006 relatif à l’établissement des cartes de bruit et desplans de prévention du bruit dans l’environnement, 2018.
[5] Besnard, F.; et al. Road noise prediction - 1 Calculating sound emissions from road trafﬁc, Editions SETRA,
2009.
[6] Pallas, M.A.; Dutilleux, G. Experimental confrontation of medium-heavy vehicle noise emission to the
CNOSSOS-EU prediction method. Euronoise 2018, Heraklion, Crete, Greece, 2018.
[7] Pallas, M.A.; Le Bellec, A. Determination of a noise emission model for French medium-heavy vehicles.
Internoise 2019, Madrid, Spain, 2019.
[8] Peeters, B.; Van Blokland, G.J. Correcting the CNOSSOS-EU road noise emission values. Euronoise 2018,
Heraklion, Crete, Greece, 2018.
[9] Reken- en meetvoorschrift geluid 2012, Bijlage VII - Karteringsvoorschriften. https://wetten.overheid.
nl/BWBR0031722/2019-01-01#BijlageVII, consulted on 27/05/2019.
[10] Dutilleux, G.; Soldano, B. Matching directive 2015/996/EC (CNOSSOS-EU) and the French emission
model for road pavements. Euronoise 2018, Heraklion, Crete, Greece, 2018.
[11] Kok, A. Reﬁning the CNOSSOS-EU calculation method for environmental noise. Internoise 2019, Madrid,
Spain, 2019.
[12] NF EN ISO 11819-1, Acoustics – Measurement of the inﬂuence of road surfaces on trafﬁc noise – Part 1:
Statistical Pass-By method, 2002.
[13] NF 31119-2, Acoustics - In situ characterisation of the acoustic performance of road surfaces - Pass-by
measurements - Part 2 : Controlled vehicles (in French), 2000.

3629