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Reduction of road traffic noise by source measures —present and
future strategies
Truls Berge
a)
, Piotr Mioduszewski
b)
, Jerzy Ejsmont
c)
and Beata Świeczko-Żurek
d)
(Received: 2 May 2017; Revised: 13 November 2017; Accepted: 13 November 2017)
The current trend worldwide is less focused on reducing road trafficnoise.Thisis
in strong contrast to the severe impact of traffic noise to the general health and
quality of life. A more holistic and combined strategy is needed. Current interna-
tional rules and regulations regarding vehicles and tyres are not sufficient to reduce
traffic noise levels in an effective way. Calculations show that these regulations will
only yield a reduction of approximately 1.5 dB in L
den
levels for urban traffic. Ad-
ditional measures need to be implemented. By combining optimized tyres and road
surfaces, a noise reduction of 4–6 dB can be achieved. Such tyres are currently being
developed for electric and hybrid-electric vehicles. In addition to noise reduction,
these tyres have less rolling resistance that can reduce vehicle energy consumption
up to 15% on normal road surfaces. However, there are several obstacles still to be
removed, such as the effectiveness of the EU tyre labeling system, and the implemen-
tation and durability of low-noise road surfaces. These challenges are discussed in
the article. © 2017 Institute of Noise Control Engineering.
Primary subject classification: 52.3; Secondary subject classification: 08
1 INTRODUCTION
In addition to air pollution, road traffic noise is the most
severe environmental impact in the urban areas worldwide
1
.
Road traffic noise is an important source of increased health
risk and reduced quality of life for millions of people, ex-
posed even to moderate noise levels.
In Europe, The European Environmental Agency (EEA)
has estimated that more than 125 million people are ex-
posed to noise levels above accepted limits
2
.Thisisnearly
one out of every four inhabitants.
The effects of noise are particularly widespread. For the
one in four Europeans exposed to noise levels above the
EU's threshold for assessment and action, there are both di-
rect and indirect health effects. Traffic noise annoys almost
20 million Europeans and disturbs the sleep of an estimated
8 million. Environmental noise is also linked to approx-
imately 43,000 hospital admissions, 900,000 cases of hy-
pertension, and up to 10,000 premature deaths per year
2
.
AccordingtotheWorldHealthOrganization(WHO)
L
den
levels above 65 dB and L
night
levels above 55 dB will
increase the risk of cardiovascular diseases with 20–40%
1
.
WHO has estimated that between 1 and 1.6 million
healthy life years (DALYs) are lost every year in EU,
due to traffic noise exposure. One healthy life year has
been estimated to cost 40,000 to 80,000 Euros (based
on air pollution data). This means that the costs of noise
exposure in EU can be valued to be in the region of 40
to 80 billion Euros per year, if the estimate of 1 million
lost healthy years is used.
There is a significant health burden also among people
exposedtonoiselevelsbelow55dBL
den
. The health risks
for one person are lower for these lower noise levels, but
the number of people exposed to these noise levels is much
larger. The overall health burden for this group, therefore, is
still quite large. In the EEA, data are extrapolated to lower
noise levels than those that are mandatory in the Environ-
mental Noise Directive (END) and included in the health
impact assessment. The estimation is that the results increase
further with about 25% for severe annoyance and 70% for
severe sleep disturbance. For hypertension, hospital admis-
sions and premature mortality, the increase is about 10%
3
.
2 TRAFFIC NOISE WORLDWIDE
Even if the effects of noise are now well-known facts,
there seems to be a lack of a common strategy in Europe
a)
SINTEF Digital, P.O. Box 4760, Torgarden, NO-7465
Trondheim, NORWAY; email: truls.berge@sintef.no.
b)
Faculty of Mechanical Engineering, Gdansk University of
Technology, ul. Narutowicza 11/12, Gdansk, POLAND;
email: pmiodusz@pg.gda.pl.
c)
Faculty of Mechanical Engineering, Gdansk University of
Technology, ul. Narutowicza 11/12, Gdansk, POLAND;
email: jejsmont@pg.gda.pl.
d)
Faculty of Mechanical Engineering, Gdansk University of
Technology, ul. Narutowicza 11/12, Gdansk, POLAND;
email: beazurek@pg.gda.pl.
549Noise Control Engr. J. 65 (6), November-December 2017 Published by INCE/USA in conjunction with KSNVE
and other regions to reduce the impact of road traffic
noise. The priority seems to be limited to climate change
and reduction of greenhouse gases.
For traffic noise, the situation for some regions/countries
can be summarized as follows:
- European Union: Some important projects were
finalized in the last couple of years, such as
PERSUADE (2015), ROSANNE (2016) and the
CEDR projects DISTANCE, ON-AIR, QUESTIM
and FOREVER (2015). No new major projects
seem to be ongoing, except LIFE Nereide proj-
ect, which regards durable and sustainable low-
noise road surfaces using recycled asphalt and
crumb rubber from scrap tyres
4
,andinthere-
search program Horizon2020, there are presently
no calls related to road traffic noise. However,
the CEDR Road Noise group will continue to
work for the next few years. Plans for a Project
Call for Road Noise are currently being drafted
and, if approved by the governing board, a call for
projects will come in 2018. In addition, there seem
to be some national projects on low-noise road sur-
faces running in Germany, Netherlands, Belgium
and in Switzerland. In 2017, all EU and the Europe
Economic Agreement member states shall make a
new mapping of the noise situation for L
den
levels
above 55 dB and L
night
levels above 50 dB, accord-
ing to the Environmental Noise Directive 2002/49/
EC. The action plans shall be finalized in 2018.
There are no legal processes to ensure that these
action plans will be followed up in practice, and
thus there is no guarantee that the mapping process
and action plans will ensure a reduction of noise
levels in practice or even compensate for increased
traffic volume and densification of cities (more
people living close to major roads).
- Nordic countries: In Norway, the number of peo-
ple exposed to noise levels above L
den
55 dB has
increased by approximately 54% between the year
1999 and 2014. The goal is to reduce the number
of people exposed to noise with 10% in 2020,
based on a special national noise exposure index
(SPI). Even if there are action plans available,
there is presently no research activity going on,
to meet the national goals. In Denmark, the activ-
ity of the Danish Road Directorate on road traffic
noise has dramatically been reduced. Presently,
there seems to be a much higher priority on re-
ducing CO
2
emissions from the road traffic.
- Japan: Previous research activity on poroelastic
road surfaces (PERS) has been terminated. The
general trend is less focused on projects reducing
road traffic noise.
- United States: On a federal level, reduction of
traffic noise has never been an important issue.
General noise limits have only been established
for heavy trucks. In some states, like Arizona,
tests of low-noise pavements have been going on
for some time. With the election of Donald Trump
as the president, there is less likely that the federal
Environmental Protection Agency (EPA) will fo-
cus more on environmental issues like road traffic
noise. President Trump has proposed severe cuts
in the budget of EPA.
3 VEHICLE NOISE SOURCES AND
TRAFFIC NOISE PREDICTION MODELS
Road traffic noise in urban areas is dominating by two
independent sources on a vehicle:
- Powertrain related sources
- Tyre/road interaction—rolling noise sources
Both sources are vehicle speed dependent, and the con-
tribution of each source is different for different vehicle
categories. Based on a large number of measurements, a
relationship between these two main sources and vehicle
speed has been established for use in traffic noise predic-
tion models. Figure 1 shows an example of this relation-
ship, based on the Nord2000 prediction model
5
.
The cross-over speed, where both sources have equal
contribution to the total noise, is approximately 35 km/h for
passenger cars and 60 km/h for heavy vehicles. The vehicle
noise emission data, which are the basis for the Nord2000
model (and models like CNOSSOS-EU
6
), are based on
measurements performed 10–15 years ago
7
. Since then,
there has been a continuous development of more silent
engines and propulsion systems, mainly due to more strin-
gent exhaust emission regulations. In order to meet Euro
VI limits for exhaust emission, Volvo needed to increase
the volume of the muffler on their trucks. By doing so,
they could reduce the exhaust noise with approximately
10 dB in the low frequency range
8
.Thisreductionof
noise of powertrain related sources will obviously shift
the cross-over speed for the example given in Fig. 1 to a
lower value. A lower cross-over speed means that the im-
portance of the tyre/road noise component is increasing
also in urban and residential areas, where the general speed
is within the range of 20–40 km/h.
ThedatashowninFig. 1 are based on steady speed con-
ditions. If there are frequent stop-and-go traffic conditions,
the importance of powertrain noise sources will increase,
due to accelerating and decelerating vehicles.
In a recent Swiss research project,
9,10
the acoustical
performance of low-noise road surfaces at speeds below
550 Noise Control Engr. J. 65 (6), November-December 2017 Published by INCE/USA in conjunction with KSNVE
50 km/h has been studied. The effect of such low-noise
road surface depends very much on the cross-over vehicle
speed, as shown in Fig. 1. To study this cross-over speed
for light vehicles, a measurement program of 22 light vehi-
cles was conducted. The vehicle fleet consisted of two elec-
tric and two hybrid vehicles, one light duty commercial
vehicle with diesel engine and the rest with diesel or petrol
engines. The majority of vehicles were 2012–2014 models
and they were measured on a closed test track. To separate
the rolling noise and the propulsion noise, both Coast-by
(engine off) and Controlled Pass-by (engine on) mea-
surements were made in the speed range between 0 to
60 km/h. To study the influence of traffic lights, speed
bumps, etc. where uneven driving conditions can occur,
two different acceleration modes were implemented: pru-
dent or impetuous. Figure 2 shows the results for the vehi-
cles with petrol and diesel engines. The rolling noise levels
are referred to the road surface used in CNOSSOS-EU,
which is DAC0/11 or SMA0/11, 2–7 years old
9
.
The results show that the cross-over speed was found to
be 15.2 km/h for petrol cars and 15.9 km/h for diesel cars.
For the light duty commercial vehicle, the cross-over speed
was 33.7 km/h. This is significantly lower than the present
data used in models like Nord2000 or CNOSSOS-EU.
This indicates that these models underestimate the effect
of reducing the tyre/road noise contribution at lower speeds
on the total noise level (combined power-unit noise and
tyre/road noise).
Presently, there is a lack of similar data for heavy ve-
hicles. In a recent Nordic project on tyres, NordTyre, a
measurement campaign was conducted on a heavy truck,
tested with 30 different tyres
11
. The tyres were tested
on SMA0/11 surface, as well as on other road surfaces,
including ISO 10844
12
. On average, the tyre/road noise
level at 7.5 m distance (coast-by measurements) was
77.7 dB(A) at 70 km/h, with a standard deviation of
1.0 dB. Measurements were performed in the speed range
from 35 to 75 km/h. A comparison of the measured values
for a single tyre, compared to a standardized tyre noise
level vs. speed relationship in Nord2000, is shown in
Fig. 3. The difference is within the range of 5 dB. This
indicates an overestimation of the tyre/road noise com-
ponent in the prediction models, also for heavy vehicles.
This again would underestimate the effect of a noise re-
ducing pavements. However, this comparison should be
verified through a similar test program for heavy vehi-
cles as conducted for light vehicles in Switzerland.
4 CURRENT STRATEGIES TO REDUCE
ROAD TRAFFIC NOISE
The most cost-efficient strategy to reduce road traffic
noise is the source noise reduction
13
. Since the noise
sources of a vehicle are primarily related to the power-
train sources and to the rolling noise, the most effective
source reduction strategy would be:
- to use low-noise vehicles
- to use low-noise tyres
- to use low-noise road surfaces
Fig. 1—Propulsion noise (Prop), tyre/road
noise (Roll) and total noise (Tot) for
passenger cars (P) and heavy vehicles
(H). Data based on the Nord2000
prediction model; distance, 7.5 m.
Fig. 2—Rolling noise (red) and propulsion noise
in driving gears (grey) as weighted
gears (green) as well as the total noise
(black) from petrol and diesel cars.
551Noise Control Engr. J. 65 (6), November-December 2017 Published by INCE/USA in conjunction with KSNVE
The maximum is a combination of all three, for exam-
ple, an electric powered vehicle, using tyres with the pres-
ent lowest tyre/road noise level on a porous road surface.
This seems reasonable simple, but there are major
questions and challenges to this:
1) Low-noise vehicles:
What is a low-noise vehicle? A vehicle that fulfils al-
ready Phase 3 (from 2024/26) of the present international
vehicle regulations EU 540/2014 or ECE Reg.51-03?
Phase 3 vehicles will have a type approval level 3–4dB
below the present limit. However, the limits of Phase 3 are
still subjected to a cost/benefit evaluation before approval.
The EU/ECE regulations are based on a revised ISO type
approval test procedure
14
, which simulates real world ur-
ban driving conditions better than the old system. In a
Polish-Norwegian research project, LEO (www.leo.mech.
pg.gda.pl), the effect on L
den
levels of the approved noise
limits of EU/ECE (including Phase 3 for vehicles and
adopted limits for tyres), has been calculated up to the
year 2030
15
. The calculations have been made for differ-
ent road categories and for the present vehicle fleet in
Norway and in the EU, using the German traffic noise
calculation model TraNeCam.
The reduction of A-weighed levels of L
den
(dB) rela-
tive to 2016 is shown in Fig. 4, with separate results for
Norway and EU. The reason for separate calculations is
that in Norway, already 2% of the fleet is electric vehi-
cles and the average age of cars is somewhat higher than
the average of EU. The reference surface is SMA0/11,
and due to the road conditions in Norway, the rolling
noise part in the model is somewhat higher. In Fig. 4,
the calculations are shown for two urban road categories
(city trunk road and residential road). No general increase
in the total number of vehicles (traffic volume) is included
in these calculations.
Even with a reduction of the limits of 3–4dB,theeffect
on the L
den
levels is rather small, in the range of 1.5 dB. It
should be noted that these calculations do not consider any
increased number of EVs/PEHVs in the trafficfleet. How-
ever, both in the project LEO and in the CEDR project
FOREVER
16
, the increased number of EVs has shown a
marginal effect on L
den
. With up to 25% share of EVs in
the fleet, the expected reduction is less than 0.5 dB. This
is due to the domination of tyre/road noise. However, if
the EVs are combined with low-noise tyres, the reduction
will be larger, as shown in Sec. 5.1. For the calculation of
L
den
for all vehicle categories as shown in Fig. 4,thereis
no difference in levels between Norway and EU. However,
if only passenger cars are compared, the effect of low-noise
tyres for EVs and a porous road surface will give approx-
imately 1 dB higher reduction of L
den
levels in Norway
compared to EU. This is mainly due to a higher volume
of electric cars in the vehicle fleet in Norway.
However, there are still challenges related to reduction
of vehicle noise:
Annoyance from road traffic, especially during evenings/
nights, can often be related to single events. This could
Fig. 3—The rolling noise level as a function
of vehicle speed of a truck tyre
measured in the NordTyre project
(blue) compared to the normalized
curve for rolling noise for heavy
vehicles in the Nord2000 model (red).
Fig. 4—Calculations of the expected noise
reduction of L
den
, due to the accepted
and proposed noise vehicle limits in
EU/ECE regulations for two different
road categories.
552 Noise Control Engr. J. 65 (6), November-December 2017 Published by INCE/USA in conjunction with KSNVE
be vehicles with non-legal replaced silencers, high ac-
celeration driving styles, etc. Neither of these types of
events is connected to type-approval legislation of new
vehicles. Except for mopeds and motorcycles, all vehi-
cles in the EU region more than 3 years old are called
in for a periodic technical inspection. External noise is
one of the parameters to be evaluated. It is doubtful if
this inspection is effective to reduce abnormal noise be-
havior of vehicles in traffic. It is well-known that many
of the motorcycles in-use have modified (and very noisy)
exhaust systems. Only random road-side inspection of
such vehicles can reveal non-legal and noisy vehicles.
An improved simplified noise test should also be devel-
oped, as the present noise inspection is based on a station-
ary tests of vehicle exhaust system noise (measured close
to the exhaust pipe) and is not very well correlated with
pass-by tests (manly due to a test with little or no-load
on the engine).
2) Low-noise tyres:
The noise from tyres is regulated by UN ECE Reg.117
17
.
New noise limits were adopted in 2014 (C1/C2 tyres) and
2016 (C3 tyres). Stage 2, with a reduction in the range of
2–4 dB, will be introduced in 2018/2020.
In the EU, a regulation on the labeling of tyres was intro-
ducedin2012
18
. This regulation specifies a labeling sys-
tem and limits for rolling resistance, wet grip and noise.
The rolling resistance is based on laboratory measurements
(drum)andthenoiseismeasuredonanISO10844surface
(smooth). The values for rolling resistance is labeled with
A to G, where A is the best (since January 11, 2012 the G
label is not used any more). Similar labels A to G are spec-
ified for wet grip where the F and G labels had been with-
drawn in January 11, 2014. For noise, the symbol for the
different noise classes is marked as shown in Fig. 5.
One bar means a label value of 3 dB or more below the
limit, two bars mean 1–2 dB below or at the limit and three
bars mean a noise level exceeding the limits.
For a new vehicle, the manufacturer fits the tyres as
OE-tyres (Original Equipment). They shall meet a wide
set of requirements from the vehicle manufacturer, and
the three items in the labeling regulation are just a few of
those. In addition to the tyre noise limit (set at 80 km/h for
passenger car tyres), the combined tyre and vehicle must
meet the noise regulation for vehicles (EU/ECE), which
normally is type approved at a speed around 50–60 km/h
(category M). To have a certain margin for the contribu-
tion from the powertrain (internal combustion engines),
the demands from the vehicle manufacturer on the tyre
supplier may then be more stringent than the actual tyre
noise regulations.
To choose replacement tyres is not straightforward for
the normal car owner. For many, the price is a prime param-
eter. If comfort is a main issue, the customer may look at
the label value. However, this label value is related to the
external noise level, and it does not necessarily correlate
with the internal noise level. But even if the customer
chooses a tyre with the best noise label value (one bar
and for example a label value of 66 dB, which presently
is the lowest value on the market
19
), it is no guarantee that
this tyre will contribute to a general reduction of traffic
noise. Several investigations
20–22
have demonstrated the
lack of correlation and ranking of tyres on the ISO surface
and on real road surfaces (see Fig. 6). In some of these
projects, the noise has been measured using a CPX trailer
and not fitted at a vehicle, as specified in the UN ECE.
Reg.117. The load and tyre pressure could deviate from
this regulation, and then the tyre contact area could be dif-
ferent. This has been a major criticism from the industry
and the main explanation for the lack of correlation. How-
ever, additional measurements where the load and tyre
pressure was adjusted did not improve this correlation
23
.
In the LEO project, passenger car tyres were mea-
sured on drums at the facilities of Technical University of
Gdansk (TUG) in Poland on replicas of different road sur-
faces. In Fig. 7, a regression analysis has been presented
between measured sound pressure levels on a replica of
an SMA0/8 surface (with similar maximum aggregate size
as the ISO surface) and the EU label values
24
.Thisanalysis
confirms the lack of correlation, also when drum measure-
ments are being made.
In the NordTyre part 2 project, 31 passenger car tyres
were measured on different normally used road surfaces
in the Nordic countries (dense asphalt concrete surfaces
and stone mastic surfaces with maximum chipping sizes
from 6 to 16 mm). In addition, measurements were also
made on two different ISO tracks
21
. In all these measure-
ments, two CPX trailers were used: the trailer of the Dan-
ish Road Directorate (trailer without an enclosure) and the
trailer of the Norwegian Public Roads Administration
(trailer with a protective chamber). Since the load and
the tyre pressure are somewhat different from the specifi-
cations in the ECE tyre regulation, the results were theo-
retically adjusted to compensate for this deviation, using
correction factor of 1.4 dB per 100 kg load for each indi-
vidual tyre. The analysis showed that the variation in label
values could only explain less than 10% of the variation in
measured CPX levels, no matter if the results had been cor-
rected or not for deviations from the specified load in the
Fig. 5—EU tyre labeling of noise levels.
553Noise Control Engr. J. 65 (6), November-December 2017 Published by INCE/USA in conjunction with KSNVE
ECE tyre regulation. Figure 8 shows the correlation be-
tween measured (and corrected for load deviations) CPX
levels on the two ISO surfaces and the label values. There
is an obvious lack of correlation. Doing such a regression
analysis with normally used SMA0/11 surfaces shows an
even worse correlation and difference in ranking order.
Some investigations
11,25
show that the correlation is im-
proved if a comparison is made between measured values
on an ISO 10844 surface and values from similar measure-
ments are made on a smooth DAC0/8 or SMA0/8 surface.
In these investigations, the equipment, tyre pressure and
loading have been identical.
In a Swedish investigation
22
, not only the correlation of
measured noise (CPX levels) with the labeled values, but
also the correlation of measured and labeled values for roll-
ing resistance was investigated. For the labeled values, the
rolling resistance was measured on laboratory drum facili-
ties. These values were compared to rolling resistance values
obtained on real roads (trailer measurements; see Fig. 9).
Same as for noise, there is a lack of correlation between
measured and labeled values.
3) Low-noise road surfaces:
To reduce road traffic noise and in particular the tyre/
road component, the use of low-noise road surfaces is a
well-established technology. Such surfaces can be a thin
layer with optimized texture, single or two-layer porous
surfaces or dense asphalt road surfaces with maximum
chipping size in a range of 4–8 mm. Such surfaces will nor-
mally reduce the tyre/road noise in the range of 1–5dB.
Another type of surface is the poroelastic surface (PERS),
which can give substantial reduction of noise levels from
8upto12dB
26,27
. However, this type of surface is still at
anexperimentalstageandhasnotyetbeenusedasacon-
ventional low-noise road surface. The biggest challenges
are lack of durability and high costs. In the Nordic coun-
tries (except for Denmark), with winter conditions and
studded tyres, there are still big challenges to implement
traditional low-noise road surfaces. Tests with porous
surfaces have shown that the surfaces are clogged after
only one or two winter seasons, and then the noise re-
duction is severely reduced
28
. Mainly because of these
experiences, there is no demand to invest in low-noise
Fig. 6—Correlation between measured CPX levels and EU label values. The road surface is a
smooth SMA0/8 surface.
Fig. 7—Correlation between tyre label values
and CPX values on a replica of
SMA0/8 surface.
554 Noise Control Engr. J. 65 (6), November-December 2017 Published by INCE/USA in conjunction with KSNVE
surfaces now neither from the road owners nor from the
road building companies.
In the ROSANNE project
29,30
, a proposal for the meth-
ods to be used for a future noise classification system for
road surfaces has been launched
29
. The Netherlands has
also proposed a labeling system for roads in the same
manner as for tyres
31
(see Fig. 10). In addition to noise,
a label for rolling resistance, wet skid resistance and life
span are parts of the proposed system. A road character-
ization and classification system is currently developed
by CEN TC227/WG27. This work is fundamental for a
labeling system, as proposed by the Netherlands, and if
such a classification system is combined with economic
incentives, e.g., financial support from road owners to
the road contractors, this could perhaps motivate the use
of such low-noise surfaces and to find good solutions for a
Nordic winter climate and for all other European countries
as well.
5 POSSIBILITIES FOR THE FUTURE
5.1 Noise Reduction
The previous section has shown challenges regarding
source related measures to reduce road trafficnoise.The
most efficient measure is to adopt a holistic approach
for noise reduction and avoid sub-optimization. Since
there are separate regulations for vehicles and tyres (and
no regulations for road surfaces), there is certainly a risk
Fig. 8—Correlation between measured CPX levels on two ISO tracks and label values. All
measured levels have been theoretically adjusted to correct for deviation of load according
to the UN ECE Reg.117.
Fig. 9—Correlation of labeled values of rolling resistance (left) and labeled rolling noise levels
(right) with measurements on real roads.
555Noise Control Engr. J. 65 (6), November-December 2017 Published by INCE/USA in conjunction with KSNVE
for sub-optimization, since these regulations are based on
an “artificial”ISO surface.
The vehicle fleet will change dramatically over the next
couple of decades, with an increased fleet of pure electric,
plug-in hybrid-electric and fuel cell (hydrogen) vehicles.
Due to strong user and financial incentives, more than
50% of the new vehicles sold in Norway are presently
of the abovementioned types, the majority being plug-in
hybrids. To reduce the energy consumption, the tyre in-
dustry has developed special tyres to be used on these
vehicles. Examples of such tyres are Conti.e-Contact (OE-
tyres for VW e-Golf), Bridgestone Ecopia EP500 (OE-
tyres for BMW i3) and Michelin Energy E-V (OE-tyres
for Renault Zoe). Another example of expected future
changes in the vehicle fleet is the France ban of petrol/
diesel engines sales from 2040. Similar proposals have also
been made in other European countries (France, Germany).
In Norway, the aim is that already from 2025, all new vehi-
cles shall be the zero-emission vehicles. Volvo has stated
that they will produce only electric and plug-in hybrid vehi-
cles from 2019
32
.
One of the aims of the LEO project was to provide de-
cision makers, road builders, local authorities and vehicle
users with information related to optimal road surface and
tyre selection for urban and suburban areas with strong
emphasis on electric and hybrid vehicle use. The main in-
tention was to present available technology of combined
tyres and road surfaces, which could show a potential noise
reduction and reduced energy consumption (low rolling re-
sistance) beyond the average situation today.
Measurements of noise levels (CPX and coast-by) were
made on regular existing roads in Norway and Poland and
on the drum facilities of TUG
33
. Both the special EV tyres
and selected normal passenger car tyres were tested. On
most of the regular road surfaces, the EV tyres are the
quietest or among the quietest tyres. In the laboratory drum
measurements, there is almost no difference. In Fig. 11,the
noise levels of the quietest (EV) tyres are compared with
the results for the average tyres and with the noisiest tyres
on four different road surfaces; PERS (poroelastic surface),
DPA (double layer porous asphalt), SMA0/8 and SMA0/
16. The figure shows that on the poroelastic surface
(PERS), the EV tyres are 14 dB quieter than the noisiest
tyres on the SMA0/16 surface.
By using the German traffic noise calculation program,
TraNeCam, it is possible to estimate the effect of different
measures to reduce the noise for future situations. In the
LEO project, four different scenarios have been set up
Fig. 10—Proposal from the Netherlands for a labeling system for road surfaces.
556 Noise Control Engr. J. 65 (6), November-December 2017 Published by INCE/USA in conjunction with KSNVE
for prediction of changes in the L
den
levels from 2016 to
2030:
1. Basic scenario: no additional measures, only the ef-
fect of approved changes in the vehicle and tyre reg-
ulations (EU/ECE); reference surface: SMA0/11
2. SMA0/11 + tyres for EVs; estimated source reduc-
tion (rolling noise): 2 dB
3. SMA0/8 surface + tyres for EVs; estimated source
reduction: 4 dB
4. Double layer porous surface (DPAC) + tyres for
EVs; estimated source reduction: 8 dB
The results of performed calculations are shown in
Fig. 12. The effect of vehicle and tyre regulation is expected
to a noise reduction of L
den
around 1.5 dB in 2030. By
changing the reference surface to an SMA0/8, combined
with low-noise tyres for EVs, this will give a possible re-
duction of L
den
of approximately 3 dB. This reduction
includes the effect of EU/ECE regulations. With the best
combination of tyres and a double layer porous surface,
a reduction of more than 6 dB can be achieved. The cal-
culation has been done for urban/city traffic in the speed
range of 30–50 km/h
15
. It should be stated, however, that
this is clearly a theoretical value, and should be consid-
ered as such. In reality, the reduction will depend on vari-
ables connected to noise performance of both, vehicle
tyres and road surfaces, over their lifetime.
5.2 Rolling Resistance Reduction
Both in the LEO project and in the ROSANNE project,
the coefficient of rolling resistance (CRR) of selected tyres
has been measured on a wide range of surfaces
34
.Measure-
ments have been done both using the TUG trailer and by
measurements on their laboratory drum facilities.
Proper selection of tyres for electric vehicles combined
with optimized road surfaces may lead to very substantial
energy savings but on the other hand, improper selection
may result in great losses. On the best pavements, the tyres
designed for electric vehicles may reach CRR = 0.004
which corresponds to energy savings (in relation to typical
road/tyres combinations) of about 15%. This corresponds
to a reduction of fuel consumption by 2–3%. At the same
time, improper selection of tyres and road surfaces may
lead to increase of CRR by 12% (see Fig. 13)
15
.Thisshows
how important it is to use low rolling resistance road sur-
faces on urban and suburban roads and energy saving “Elec-
tric Vehicle Tyres”on electric, hybrid and conventional cars
used primarily for urban and suburban driving.
6 CONCLUSIONS
In the next few decades, we predict a huge change in the
transportation systems. The growing fleet of low- and zero-
emission vehicles, autonomous vehicles, on-demand public
transit, integrated bicycle networks, etc. will certainly lead
to a revolution in the transportation situation in the future.
It is obvious that these changes can have a major influence
on the traffic noise development. Is a car-free city the goal
to improve the quality of life of citizens in a sustainable
way? At the same time as this may change in the way we
organize the transport, the population increases and people
are moving towards the cities. These developments will not
necessary lead to less road traffic, or a “car-free”city. Thus,
the way we organize the transportation system needs to
counteract a further increase in trafficvolume.
The currently available traffic noise prediction mod-
els do not reflect these changes. In some of the models,
only a certain increase in traffic volume per year is used
as a parameter for future situations.
Today's situation for source related measures to reduce
traffic noise could be summarized as follows:
- Vehicles and tyres —international regulations:
The approved noise regulations and limits for
the future will give only a minor reduction of
Fig. 11—CPX levels for three groups of tyres
on four different road surfaces.
Fig. 12—Calculation of reduction of L
den
levels
for four different scenarios.
•
557Noise Control Engr. J. 65 (6), November-December 2017 Published by INCE/USA in conjunction with KSNVE
L
den
levels. Additional measures need to be adopted.
If zero-emission vehicles are combined with low-
noise tyres and optimized road surfaces, there is
a great potential to reduce road trafficnoise.Many
of such vehicles do not need tyres certified for a
maximum speed of more than 200 km/h, as most
of European countries have now a maximum speed
limit of 110–140 km/h. Lower speed index gives
the tyre manufacturers a wider set of tools to re-
duce the noise, without losing other important fea-
tures of the tyres.
- Vehicles-in-use: Improvements in periodical checks
and in road-side measurement procedure are neces-
sary to ensure that the noise of vehicles does not in-
crease during the lifetime. A special focus should
be on mopeds and motorcycles, as they are not part
of the periodical technical inspection in EU.
- Road surfaces: Except for a few countries, like the
Netherlands, low-noise surfaces are still not in
widespread use. The most obvious reasons are in-
creased costs and reduced lifetime compared to
the most commonly used dense pavement types.
Increased costs need to be compensated, for exam-
ple, by economic incentives. Durability of open
porous surfaces is still a problem in the Nordic
countries (with exception for Denmark), due to
the use of studded tyres. More research is needed
to find good solutions for these winter conditions.
In the PERSUADE project, some laboratory results
using a studded tyre and PERS showed very prom-
ising results indicating a substantial increase in
wear resistance compared to normal dense sur-
faces, mainly due to the elasticity of this surface
27
.
- Avoid sub-optimization: Even if the traffic noise is
very much interconnected between the vehicle, the
tyre and the road, the legal system as it is today
favours a sub-optimization of noise reducing mea-
sures. Example of this is designing the noise perfor-
mance of vehicles and tyres during type approval
conditions only. As shown in this paper, there is a
poor correlation between tyre/road noise measured
onanISOsurfaceandonnormallyusedsurfaces,
like an SMA type. In a holistic approach for noise
reduction, the overall performance must be balanced
between noise, safety and overall environmental
impact. The noise reduction with the lowest trade-
off on overall environmental and safety perfor-
mance should be encouraged. The LEO project
shows the potential for such a combined approach.
The current target to reduce energy consumption
and CO
2
emission from the road traffic can be a
powerful tool to change the current trend of in-
creased number of people exposed to unhealthy
road traffic noise.
7 ACKNOWLEDGMENTS
The LEO project has been funded by the Polish Na-
tional Center for Research and Development (NCBiR)
within the Polish-Norwegian Research Program CORE,
project LEO (Grant Agreement 196195/2013).
Fig. 13—Possible energy losses and savings due to selection of tyres and road surfaces.
•
•
•
558 Noise Control Engr. J. 65 (6), November-December 2017 Published by INCE/USA in conjunction with KSNVE
8 REFERENCES
1. World Health Organization (WHO), “Burden of disease from
environmental noise. Quantification of healthy life years lost
in Europe”, (2011).
2. The European environment —State and outlook 2015 (SOER
2015). The European Environmental Agency, (2015). http://www.
eea.europa.eu/soer-2015/europe/noise.
3. A. van Beek et al., “Towards a complete health impact assessment
for noise in Europe”,Proceedings of EuroNoise 2015, Maastricht,
Netherlands, (2015).
4. P. Leandro et al., LIFE NEREIDE: “New low noise pavement
surfaces”,Proceedings of ICSV24, London, UK, (2017). www.
neideproject.eu.
5. H. Bendtsen and K. Gspan, “State of the art in managing road
traffic noise: noise-reducing pavements”, CEDR Technical Report
2017-01, (2017).
6. S. Kephalopoulus, M. Paviotti and F. Anfosso-Lédée, “Common
noise assessment methods in Europe”(CNOSSOS-EU), JRC
Report, (2012).
7. H.G. Jonasson, “Acoustic source modelling of Nordic road
vehicles”, SP Swedish National Testing and Research Institute.
SP Report 2006:12, (2006).
8. “Quieter Cities of the Future —Source Book”, CAETS Forum
on Lessening the Severe Health Effects of Traffic Noise in Cities
by Emission Reductions. Innsbruck, Austria, (2013). Report avail-
able from www.ta.chalmers.se.
9. E. Hammer, S. Egger, T. Saurer and E. Bühlmann, “Traffic noise
emission modelling at lower speeds”,Proceedings of ICSV23,
Athens, Greece, (2016).
10. S. Egger, T. Saurer, E. Hammer and E. Bühlmann, “Anew
method for reliable determination of the acoustic performance
of low-noise road surfaces at speeds below 50 km/h”,Proceedings
of InterNoise2016, Hamburg, Germany, (2016).
11. G. van Blokland, W. Schwanen, E. van Gils and M. van Blokland,
“Results of tyre noise testing for NordTyre. Part 3”, Report
M+P.DRD 13.01.4, (2015).
12. Acoustics—Specification of Test Tracks for Noise Emitted by
Road Vehicles and Their Tyres, International Standard ISO
10844: 2014, International Organization for Standardization,
Geneva, Switzerland, (2014).
13. I. Milford, K. Gspan, S. Aasebø and K. Strömmer, “Report tyre
and vehicle noise”, CEDR Final Report v2., (2013).
14. Acoustics—Measurement of noise emitted by accelerating road
vehicles—Engineering method. Part 1: M and N categories, Inter-
national Standard ISO 362-1: 2014, International Organization
for Standardization, Geneva, Switzerland, (2014).
15. T. Berge, J. Ejsmont and P. Mioduszewski, “Feasibility study
and cost/benefit analysis”, Final report. LEO-WP5-D1, (2016).
16. M.A. Pallas, J. Kennedy, I. Walker, M. Berengier and J. Lelong,
“Noise emission of electric and hybrid-electric vehicles”, Final
Report of FOREVER WP2, CEDR.
17. ECE R117 rev2, “Uniform Provisions concerning the Approval
of Tyres with regards to Rolling Sound Emissions and to Adhe-
sion on Wet Surfaces and/or to Rolling Resistance”, Document
E/ECE/324/Rev.2/Add.116/Rev.2 –E/ECE/TRANS/505/Rev.2/
Add.116/Rev.2. United Nations Economic Commission for
Europe (ECE), Geneva, Switzerland, (2011).
18. European Parliament and Council. Regulation (EC) No. 1222/
2009. Labelling of tyres with respect to fuel efficiency and other
essential parameters. Official Journal of the European Commu-
nities, (2009).
19. M.Dittrich,F.deRoo,S.vanZyl,S.JansenandE.deGraaff,
“Triple A tyres for cost-effective noise reduction in Europe”,Pro-
ceedings of EuroNoise2015, Maastricht, Netherlands, (2015).
20. J.Ejsmont,T.Berge andB.Świeczko-Żurek, “Influence of
measuring conditions on tyre/road noise”,Proceedings of
EuroRegio2016, Porto, Portugal, (2016).
21. J. Kragh, J. Oddershede and R. Stahlfest Hock Skov, “NordTyre —
Tyre labelling and Nordic traffic noise. 3rd Draft Final Report:
analysis of data on passenger car tyres”, Danish Road Directorate,
Document 13/23337-3, (2015).
22. U. Sandberg, P. Mioduszewski, J. Ejsmont and T. Vieira, “Noise
and rolling resistance of various winter tyres compared to nor-
mal car tyres”,Proceedings of InterNoise2016, Hamburg, Germany,
(2016).
23. T. Berge, P. Mioduszewski and J. Ejsmont, “Final report on
noise measurements”, LEO-WP3-D2, (2016).
24. B. Świeczko-Żurek, J. Ejsmont and G. Ronowski, “How efficient
is noise labeling of tyres?”,Proceedings of ICSV21, Beijing,
China, (2014).
25. T. Berge, F. Haukland and S. Storeheier, “Noise measurements of
passenger car tyres at the Kloosterzande test track. Noise rank-
ing, frequency and texture analysis”, SINTEF Report A19446,
(2011).
26. H. Bendtsen and R. Stahlfest Hock Skov, “Performance of eight
poroelastic test sections”, Danish Road Directorate, PERSUADE
report 31, (2015).
27. U. Sandberg, L. Goubert, K. Biligiri and B. Kalman, “State-of-
the-art regarding poroelastic road surfaces”, PERSUADE Re-
port D8.1, (2010).
28. T. Berge, F. Haukland and A. Ustad, “Environmentally friendly
pavements. Results from noise measurements 2005–2008”,
SINTEF Report A9721, (2009).
29. M. Haider, M. Conter, R. Wehr, U. Sandberg and F. Anfosso-Lédée,
“Project ROSANNE: Rolling resistance, Skid resistance and Noise
Emission measurement standards for road surfaces”,Proceedings
of InterNoise2014, Melbourne, Australia, (2014).
30. Homepage of ROSANNE project: http://rosanne-project.eu/.
31. A. de Bondt, F. Bijleveld, B. Bobbink, R. Hermsen, M. van Koeverden,
D.Schnipper and H. ter Hueme, “Labelling of road surfaces. An ini-
tiative from the Netherlands”, UN ECE Working Party on Noise
(GRB). 65th GRB Informal document GRB-65-22-Add.1, Geneva,
Switzerland, (2017).
32. A. Vaughan, “All Volvo cars to be electric or hybrid from 2019”,
The Guardian, 5 July 2017 https://www.theguardian.com/
business/2017/jul/05/volvo-cars-electric-hybrid-2019, accessed
13 November 2017.
33. J. Ejsmont, S. Taryma, B. Świeczko-Żurek and P. Mioduszewski,
“Noise generated by tyres designed for electric vehicles —Results
of laboratory experiments”,Proceedings of EuroNoise 2015,
Maastricht, Netherlands, (2015).
34. J. Ejsmont, G. Ronowski, S. Taryma and B. Świeczko-Żurek,
“Final report of rolling resistance measurements in 2013–2016”,
LEO-WP4-D1, (2016).
559Noise Control Engr. J. 65 (6), November-December 2017 Published by INCE/USA in conjunction with KSNVE
