PROCEEDINGS of the23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Recommendations for traffic noise abatement
René WEINANDY1; Hans BOEGLI2; Urs WALKER3
1

German Environment Agency, Germany

2

Swiss Federal Office for the Environment, Switzerland

3

Swiss Federal Office for the Environment, Switzerland

ABSTRACT
Since 2010 the EPA-Network Interest Group on Noise Abatement has developed various reports with bestpractice recommendations covering road, railway and aircraft noise as well as decision criteria for applying
noise abatement measures. The most important recommendations are as follows:
Road traffic noise: Further tighten limit values for road vehicles and tires, extent the knowledge of the public(both users, suppliers and other stake holders) about the noisiness class of products like vehicles and tires,continue development and application of low noise surfaces.
Railway traffic noise: substitute cast-iron block brakes with even synthetic material or disk brake andmaintain high quality wheel and rail smoothness, introduce stricter noise requirements for all existing freightwagons.
Aircraft traffic noise: Introduce tighter limit values of noise certification levels, harmonize noise categories
of aircraft, establish permanent incentives to optimize flight procedures regarding noise.
Criteria for applying abatement measures: Develop harmonized methods to determine and internalize thecosts and benefits of measures to reduce traffic noise.
Despite the best practice list, one has to be aware that the classic noise abatement procedure has to becomplemented with new innovative measures in order to face the challenge of future trends and developments.
IGNA is working on that.
Keywords: Noise abatement, Traffic noise, Quiet areas, Limit values, Cost-benefit methods

1. INTRODUCTION
Many people are exposed to high levels of noise that adversely affect their health and quality oflife. Noise is now experienced virtually every-where and around the clock, in towns and in the country,
day and night. As a result of large-scale infrastructure projects such as the construction of new airports
or the expansion of existing ones, there is much greater political, scientific, and public awareness of
the issue of noise. To a certain degree, noise is a pollutant, which has only a localized effect unlike
other pollutants but which can be found virtually everywhere as there are so many areas that areaffected by it.
Exposure to environmental noise due to transport has a negative impact on people. The World
health Organization Regional office for Europe published an overview in which four main effects are
distinguished: general annoyance due to the disturbing effect of noise on the wellbeing, interruptionof sleep during the night, stress-related effects on the cardio vascular system of humans and cognitive
impairment on children.
The increased level of noise is primarily the result of an increased volume of traffic. There are,however, a whole series of measures which can reduce noise pollution, from low -noise car tires to1rene.weinandy@uba.deHans.Boegli@bafu.admin.ch
3
Urs.Walker@bafu.admin.ch
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less noisy brakes for freight trains to strategies to avoid use of transport. It is especially important to
involve the general public as much as possible in the fight against noise. IGNA is working on that.

2. Measures to abate traffic noise
2.1 Road traffic
Although vehicle technology has advanced considerably in the last 25 years, leading to improved
mileage and gaseous emissions, the noise emission has not improved. For cars at high speed, thesituation has even worsened, as is shown in figure 1. Only for heavy duty vehicles under urban driving
situations improvements are found. This trend is in clear contradiction to the continuous tightening oftype approval limit values from 82 dB in the early eighties to 72 dB from July 1st, 2016. This paradox
can be explained by the fact that the 82 dB presented a relaxed limit value, which did not have mucheffect in terms of shifting the noise emission of the vehicle fleet. Then, additional tightening of limit
values where often bypassed with a change in test procedure or added allowances for specific vehicles.
The most important effect is that under conditions of normal driving the tires contribute most of theemission, while in the test procedure it used to be a much smaller part (1).
In figure 1, the effect of vehicle speed on the noise emission can be deduced. When going from 50
to 120 km/h the sound emission increases about 10 dB. The effect on the time -averaged road sidelevel however has to be corrected for the shorter passing time at high speed (with a factor
10·lg(120/50) dB) resulting in a net effect of 6 dB on equivalent road side levels.

Figure 1 – Noise emission of the average Dutch vehicle over the last twenty years. Road surface type is astandard Dense Asphalt Concrete 11 in all tested conditions. Each data point presents the average over 10
different test sections on highways and through roads
Recommendations for road traffic noise abatement:- Improving the source emission of cars and trucks, by tightening type approval procedures and limits
for vehicles and their tires- Stimulating the buying and usage of low noise vehicles and tires, and taxing noisy ones
- Application of noise reducing road surfaces- Reducing the driving speed- Improving driving style by suppressing high engine loads and avoiding hig h engine speeds throughgearing up quicker.
2.2 Railway traffic
Unlike road traffic noise, which occurs virtually everywhere, rail traffic noise is much more
localized to individual transport corridors. However, depending on the type of train and the volumeof trains, very high levels of noise can be generated, especially along freight corridors on which most3562

of the rail traffic is at night. One example is the Middle Rhine Valley, which is part of the European
freight corridor between Rotterdam and Genoa. In many places along this corridor, the noise levels
are essentially higher than those considered desirable to maintain good health. The noise caused byrail traffic is therefore the ecological Achilles heel of the railway. However, there are measures forthe reduction of noise emitted by rail traffic.
The main source of the noise emitted by rail rolling stock at low speeds is the engine; at moderatespeeds, it is the wheel-rail contact; and at very high speeds, it is aerodynamic noise along the lengthof the rolling stock. The most important factor for the general population in terms of noise pollution
is the rolling noise. It occurs as a result of areas of roughness on the running surface of wheels andrails and is emitted by them. The measures therefore involve preventing the formation of such areasof roughness on wheels and rails and reducing the emission and transmission of noise. In the case ofthe rails, it is also important that they are as smooth as possible. Over the past few years, there has
already been progress in this respect. New technical processes allow the manufacture of smootherrails. Measures to reduce noise emission are rail absorbers and shields as well as wheel absorbers andoptimized wheel geometries.
But the most important measure, and also the most cost-effective one, is refitting noisy freightwagons. This involves replacing the cast iron brake blocks previously used with modern composite
brake blocks, which do not roughen the surface of the wheels to the same extent and which there fore
result in a quieter rolling noise. In the case of new freight wagons, only the use of such braking
systems is permitted in any case, or of disc brakes, such as on modern railway carriages.
The establishment of ambitious noise thresholds is something that is necessary, but it does notinclude current freight wagons, which typically have an operating life of 30 to 40 years. In terms ofnoise abatement, however, they are the central problem. There is an urgent need to refit them withquieter braking systems.
Recommendations for railway traffic noise abatement:- Improving the source emission of railway stock by tightening approval procedures and limits
for new railway stock- Stimulating the usage of low noise railway stock by taxing noisy ones
- Improving the acoustic characteristics of the railway tracks- Substitute cast-iron block brakes with even synthetic material or disk brake and maintain highquality wheel and rail smoothness- Introduce stricter noise requirements for all existing freight wagons.
2.3 Aircraft traffic noise
It is not just ground-based transport that is the cause of considerable noise pollution. Many people
are also affected by aircraft noise. Unlike with road and rail traffic, in the case of aircraft, a building
has no quiet side shielded from noise, where people can sleep, for example. Protecting people fromaircraft noise at night is therefore especially important. A sufficiently long period of undisturbed sleep
is essential for mental and physical rest. Although there are individual di fferences in sleeping behavior,people on average need eight hours of unbroken sleep. The flight path can also have a considerable
impact in terms of aircraft noise on people living near airports. Different flight paths should be usedduring the day and at night in order to protect the people near airports.
All aircraft need to pass certification tests that includes noise emission. Since aircraft noise ismainly an issue around airports the noise tests are based on two noise measurements made on theground when the aircraft is taking-off (fly-over and side-line) and one measurement when the aircraftis landing (approach). In the first, and now outdated, classification of a low noise aircraft (Chapter 3)a maximum allowed noise level is defined at each of these positions. The noise values are expressedas EPNdB’s a measure that is defined slightly different from the generally used dB(A) value. The limit
levels are made dependent on the maximum allowed take–off weight and for fly-over also on thenumber of engines. Chapter 3 limits are introduced in 1972 and in 2001 a tightening was introducedwith a 10 dB lowering cumulative over all measuring positions, referred to as Chapter 4. These values
became mandatory in 2006 for all new aircraft. In 2020 an additional tightening of 7 dB (cumulativeover all measuring positions) will come into force.
Although the service life of aircraft is shorter than for rail wagons, it is longer than of road vehicles.
So in addition to improving the noise emission of new aircraft, the replacement of existing noisier3563

aircraft is also stimulated. Apart from a total ban on Chapter 2 aircraft in Europe, in about 40% of theairports the landing and take-off charges are (for a part) based on the noise category of the aircraft.
No general categorization of the noisiness of aircraft exists. In many cases the certification values areused but the definition of the categories differs, in other cases (Germany and Switzerland in particular)
the classification is based on own measurements.
For several airports, restrictions exist for the usage of noisy aircraft in the noise -sensitive nightperiod. Also at quite a few airports there exists a limit to the total number of operations (or more
effective for noise control, the total noise emission) over a yearly period. The freedom to introduce
such restrictions is however limited due to European law.
Noise abatement operational procedures include a series of measures aiming at reducing theimmission levels on the ground by optimization of the flight proc edures during take-off and landing.
Modern aircraft and airport navigation, including GPS-based steering, enable more controlled routing
both in horizontal as in vertical sense, compared to the conventional instrument -based flightprocedures. For instance with reduced drag procedures (faster retraction of flaps in take -off andreduced flap settings during approach), Noise Abatement Departure Procedures (NADP) andContinuous Descent Approach (CDA), take-off and landing operations can be performed with lessnoise impact on the ground. Specific nuisance is suppressed by restricting the use of reverse thrust
after touch down and the engine run-up before take-off. The application of such procedures must notjeopardize safety and have to be balanced against the capacity. However, with capacity very often
fixed priory and with safety as inflexible condition, there is usually very little space for to noise
optimized operational procedures.
Recommendations for aircraft traffic noise abatement:- Introduce tighter limit values of noise certification levels and the approval system for new aircraft- Harmonize noise categories of aircraft- Establish permanent incentives to optimize flight procedures regarding noise- Taxation of the usage of noisy existing aircraft.

3. Conclusions
In a comprehensive concept for noise reduction, measures to limit noise emissions based on state of-the-art technology play a particularly important role together with a reduction in the use of transport(slogan “city of short distances”) and greater use of more environmentally friendly means of transport.
These measures “at the source” have an impact everywhere and in this respect have priority before
noise mitigation barriers or soundproof windows, which only have a local impact. The goal of n oise
reduction tools is to make vehicles, their operation, and the roads or tracks on which they travel allquieter. With this in mind, noise thresholds in particular must be consistently adjusted to take into
account advances in technology. The development of technology, in turn, must be actively supportedand tax incentives used to create further technological potential for noise reduction in the future.
An essential part of a modern transparent noise reduction strategy is the direct involvement of as
many members of the public as possible. People know very well what the local noise issues are andoften already have a clear idea about how they can be resolved. Better use needs to be made of thislocal knowledge. Research into the impact of noise has shown that noise is often perceived as lessloud if people are directly involved in the decision-making process. The mutual trust of those involvedin the process is also a very important factor. A series of investigations have shown that there is acorrelation between the trust people have in the goodwill of those in positions of responsibility, orconversely their lack of trust in them, and their annoyance reaction. Trust is therefore key to theacceptance and successful implementation of noise reduction measures. Once trust has been
established with those affected, the likelihood of the relevant measure being effective is that muchgreater.

REFERENCES
1. G.J. van Blokland, “Progress report on measures on road traffic noise in the EU”, Interest Group on
Traffic Noise Abatement of the EPA Network (IGNA-EPA) March 2012,(http://epanet.pbe.eea.europa.eu/fol249409/noise/technical-report-of-measures-on-road-traffic-noise-inthe-eu.pdf ).

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