**3.4 Quiet road surfaces**

In previous paragraphs, it has already been established that the dominant noise source when driving a car at higher speeds is tire noise which is caused by friction between the wheels and the road surface. In the case of light vehicles, tire noise becomes the main noise source already at a speed of 30 km/h, while in the case of heavy vehicles at speeds higher than 60 km/h tire noise becomes the main noise source, which is shown in **Figure 16** [16]. **Figure 17** shows noise levels for different types of vehicles depending on their speed [17].

Tire noise depends on the following road surface properties:


Improving road surface properties in a way that effectively reduces noise generation and amplification will result in lower noise levels. There are several types of quiet road surfaces, and their application is mainly determined by the noise

#### **Figure 15.**

*Review of irresponsible and inappropriate traffic participants' behavior [15].*

#### **Figure 16.**

*The correlation of noise levels and vehicle's speed (lightweight vehicles marked with full lines and heavy weight vehicles with dashed lines) [16].*

reduction proportion, the permitted speed in traffic, the composition of the traffic flow, and the possible adhesion of tires to the surface during parking. In urban areas, three types of bases are most commonly used:


Thin surface layers are often referred as thin asphalt layers of or thin asphalt bases for noise level reduction (see **Figure 18**) [1]. These layers are usually up to 3 centimeters thick. There are a significant number of different types of thin surface

**91**

*Traffic Noise*

**Figure 17.**

**Figure 18.**

*DOI: http://dx.doi.org/10.5772/intechopen.92892*

layers on the market, for example, in the Netherlands more than 40, including porous and dense types. They usually reduce noise by 2–4 decibels at 50 km/h for cars when compared to the average dense asphalt concrete. Porous asphalt types are in average about 1 decibel quieter than dense ones; however they have a shorter duration than dense asphalt. The typical duration of a thin surface layer is 7–9 years. Thin surface layers are suitable and increasingly popular on low- and mediumspeed roads; however they are not appropriate for places exposed to strong stress

*Two-layer porous asphalt (on the left) and a thin surface layer of asphalt (on the right) [1].*

The two-layer porous asphalt consists of a top layer (2.5 centimeters thick) and a lower layer (4.5 centimeters thick) which is shown in **Figure 18**. The total thickness of the 7 centimeter porous layer absorbs more noise or more precisely at the beginning of its implementation from 5 to 7 decibels. Two-layer porous asphalt is relatively expensive and suitable for high-speed roads that require extreme noise reduction. Cast asphalt has a thin (3 centimeters) surface layer with a specific molding design. It contains more stone than thin surface layers, and since it is not porous, it does not absorb as much noise; however it is more robust than other

forces, such as roundabouts, steep slopes, bends, truck exits, etc.

*Noise levels for different types of vehicles, depending on their speed [17].*

**Figure 17.**

*Noise and Environment*

**90**

reduction proportion, the permitted speed in traffic, the composition of the traffic flow, and the possible adhesion of tires to the surface during parking. In urban

*The correlation of noise levels and vehicle's speed (lightweight vehicles marked with full lines and heavy weight* 

Thin surface layers are often referred as thin asphalt layers of or thin asphalt bases for noise level reduction (see **Figure 18**) [1]. These layers are usually up to 3 centimeters thick. There are a significant number of different types of thin surface

areas, three types of bases are most commonly used:

*Review of irresponsible and inappropriate traffic participants' behavior [15].*

• Thin surface layers.

*vehicles with dashed lines) [16].*

• Cast asphalt.

**Figure 16.**

**Figure 15.**

• Two-layer porous asphalt.

*Noise levels for different types of vehicles, depending on their speed [17].*

**Figure 18.**

*Two-layer porous asphalt (on the left) and a thin surface layer of asphalt (on the right) [1].*

layers on the market, for example, in the Netherlands more than 40, including porous and dense types. They usually reduce noise by 2–4 decibels at 50 km/h for cars when compared to the average dense asphalt concrete. Porous asphalt types are in average about 1 decibel quieter than dense ones; however they have a shorter duration than dense asphalt. The typical duration of a thin surface layer is 7–9 years. Thin surface layers are suitable and increasingly popular on low- and mediumspeed roads; however they are not appropriate for places exposed to strong stress forces, such as roundabouts, steep slopes, bends, truck exits, etc.

The two-layer porous asphalt consists of a top layer (2.5 centimeters thick) and a lower layer (4.5 centimeters thick) which is shown in **Figure 18**. The total thickness of the 7 centimeter porous layer absorbs more noise or more precisely at the beginning of its implementation from 5 to 7 decibels. Two-layer porous asphalt is relatively expensive and suitable for high-speed roads that require extreme noise reduction. Cast asphalt has a thin (3 centimeters) surface layer with a specific molding design. It contains more stone than thin surface layers, and since it is not porous, it does not absorb as much noise; however it is more robust than other


**Table 2.**

*Table of decibels [18].*

asphalts. A test of this type of cast asphalt conducted in Berlin resulted in an initial noise reduction of 1.5 decibels. In addition to installing quiet road surfaces, another method of reducing tire noise is the production of quiet car tires. There are several manufacturers that have developed such tires and successfully placed them on the market. In general, the comfort concept of tires is directly related to their loudness. One of the tire functions is to absorb impacts and dampen vibrations, which means that the tire is an element of the vehicle that ensures the travel comfort. Smaller wheels produce less noise. Basically, a smaller tire represents a smaller surface that adheres to the road and thus produces less noise. In addition to the size, the material from which the tire is made is also significant. There are softer types of rubber that also make less noise. Of course, one of the most important factors is the speed of driving. If one plans to drive at higher speeds, it makes sense to have tires with such performance. However, such tires are thicker and larger, thus creating more noise. Furthermore, weather conditions also play a key role in choosing tires. Tires selected for severe weather will create more noise due to certain safety aspects, i.e., the need to better adhere to the road surface. Tires selected for extreme weather conditions will make the highest noise level. According to their design, tires selected for city driving can make less noise. All of this logically implies that winter tires will make more noise than do summer tires.

Tire manufacturers can produce tires that make less noise. There are already various models, especially the quietest summer tires, which are 4–6 dB(A) below the limit, and many of the newer winter models are also approaching the limit of 2 dB(A). These restrictions are determined by Regulation No. 117 United Nations Economic Commission for Europe (UNECE)—Uniform requirements concerning the approval of tires regarding the emission of rolling sound and/or traction on rainy surfaces. The sound pressure levels generated by each tire size are shown in **Table 2** (for reinforced tires (XL), the limits are higher by 1 dB(A)) [18].

It can be concluded that noise can be limited by using modern quiet road surfaces which reduce its level from 3 to a maximum of 7 decibels. Unfortunately, such materials are usually 2.5 times more expensive than ordinary materials. Furthermore, noise can be reduced by using quieter tires by an additional 3–4 decibels; however the choice of tires depends on the preferences and habits of the driver. In the majority of cases, noise is reduced by speed limits on local roads and highways located near resident areas, and these restrictions are often even more restraining at night.

### **4. Conclusions**

Noise pollution is a serious problem that affects the overall quality of life. This problem is especially noticeable in urban areas where a significant amount of

**93**

**Author details**

Sanja Grubesa\* and Mia Suhanek

University of Zagreb, Zagreb, Croatia

provided the original work is properly cited.

\*Address all correspondence to: sanja.grubesa@fer.hr

Faculty of Electrical Engineering and Computing, Department of Electroacoustics,

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*Traffic Noise*

which they live.

*DOI: http://dx.doi.org/10.5772/intechopen.92892*

noise pollution is produced by traffic. In this chapter the main traffic sources are described and analyzed. In addition to road, railway, and aircraft noise sources, other typical noise sources common for urban areas are also discussed. Bearing in mind the serious consequences of long-term exposure to noise, it is necessary to implement at least some measure to reduce noise levels. Today there are many initiatives and plans how to tackle this issue; however this chapter has focused on measures directly connected to traffic noise levels. In that sense, this type of noise

Furthermore, it can be concluded that education and some form of encouragement are needed to get the people more involved in the "fight" against noise and its negative impact. In this way, a kind of pressure would be created to set up the necessary city infrastructure (sensor networks), and finally the citizens would obtain a much-needed improvement of the quality of life in the environments in

reduction measures has been described and discussed in detail.

### *Traffic Noise DOI: http://dx.doi.org/10.5772/intechopen.92892*

*Noise and Environment*

**Table 2.**

*Table of decibels [18].*

make more noise than do summer tires.

asphalts. A test of this type of cast asphalt conducted in Berlin resulted in an initial noise reduction of 1.5 decibels. In addition to installing quiet road surfaces, another method of reducing tire noise is the production of quiet car tires. There are several manufacturers that have developed such tires and successfully placed them on the market. In general, the comfort concept of tires is directly related to their loudness. One of the tire functions is to absorb impacts and dampen vibrations, which means that the tire is an element of the vehicle that ensures the travel comfort. Smaller wheels produce less noise. Basically, a smaller tire represents a smaller surface that adheres to the road and thus produces less noise. In addition to the size, the material from which the tire is made is also significant. There are softer types of rubber that also make less noise. Of course, one of the most important factors is the speed of driving. If one plans to drive at higher speeds, it makes sense to have tires with such performance. However, such tires are thicker and larger, thus creating more noise. Furthermore, weather conditions also play a key role in choosing tires. Tires selected for severe weather will create more noise due to certain safety aspects, i.e., the need to better adhere to the road surface. Tires selected for extreme weather conditions will make the highest noise level. According to their design, tires selected for city driving can make less noise. All of this logically implies that winter tires will

**Tire size [inches] Sound pressure level [dB(A)]**

<145 72 145–165 73 165–185 74 185–215 75 >215 76

Tire manufacturers can produce tires that make less noise. There are already various models, especially the quietest summer tires, which are 4–6 dB(A) below the limit, and many of the newer winter models are also approaching the limit of 2 dB(A). These restrictions are determined by Regulation No. 117 United Nations Economic Commission for Europe (UNECE)—Uniform requirements concerning the approval of tires regarding the emission of rolling sound and/or traction on rainy surfaces. The sound pressure levels generated by each tire size are shown in

Noise pollution is a serious problem that affects the overall quality of life. This

problem is especially noticeable in urban areas where a significant amount of

**Table 2** (for reinforced tires (XL), the limits are higher by 1 dB(A)) [18]. It can be concluded that noise can be limited by using modern quiet road surfaces which reduce its level from 3 to a maximum of 7 decibels. Unfortunately, such materials are usually 2.5 times more expensive than ordinary materials. Furthermore, noise can be reduced by using quieter tires by an additional 3–4 decibels; however the choice of tires depends on the preferences and habits of the driver. In the majority of cases, noise is reduced by speed limits on local roads and highways located near resident areas, and these restrictions are often even more

**92**

restraining at night.

**4. Conclusions**

noise pollution is produced by traffic. In this chapter the main traffic sources are described and analyzed. In addition to road, railway, and aircraft noise sources, other typical noise sources common for urban areas are also discussed. Bearing in mind the serious consequences of long-term exposure to noise, it is necessary to implement at least some measure to reduce noise levels. Today there are many initiatives and plans how to tackle this issue; however this chapter has focused on measures directly connected to traffic noise levels. In that sense, this type of noise reduction measures has been described and discussed in detail.

Furthermore, it can be concluded that education and some form of encouragement are needed to get the people more involved in the "fight" against noise and its negative impact. In this way, a kind of pressure would be created to set up the necessary city infrastructure (sensor networks), and finally the citizens would obtain a much-needed improvement of the quality of life in the environments in which they live.
