Noise and environment: scenario



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Noise and environment: scenario

European Union policies lead to the implementation of the Directive 2002/49/EC (END), which requires the adoption of action plans by the Member States, based upon noise mapping results, with a view to preventing and reducing environmental noise where necessary and particularly where exposure levels can induce harmful effects on human health and to preserving environmental noise quality where it is good. Urban noise is in fact one of the main problem reported by citizens and the World Health Organization has repeatedly pointed out the health risks associated with exposure to noise. Recent document by WHO European Centre for Environment and Health (Burden of disease from environmental noise: Quantification of healthy life years lost in Europe, 2011, and Night Noise Guidelines for Europe, 2009) reported methods to evaluate these effects on population exposed. 

The “Noise in Europe 2014”report of the European Environment Agency, collecting data received by EU Commission due to the EU Directive, provides data to confirm that road traffic is the most dominant source of environmental noise with an estimated 125 million people affected by noise levels greater than 55 dB(A) LDEN (day-evening-night level), and 40 million of that leaving near main roads. Following the previous documents edited by WHO, it is estimated that environmental noise causes at least 10 000 cases of premature death in Europe each year and that almost 20 million adults are annoyed and a further 8 million suffer sleep disturbance due to environmental noise. Furthermore, over 900 000 cases of hypertension are caused by environmental noise each year. 

 

 
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The realization of porous asphalt pavement that are soundproofing is one of the most popular solutions to mitigate noise pollution in urban areas. In fact, in these areas it is not possible to install acoustical barriers, and the installation of soundproof windows is much more expensive; particularly this latter solution doesn’t solve the problem because in many buildings windows are open in summer and people are still annoyed.

The new pavements intended to be developed in the project will improve the actual performances reducing annoyance in urban context, with a particular attention to the disturbance perceived by population. In particular, sites will be selected between critical areas identified by regional road action plan available on the Toscana website with a full explanation of the exposure of every candidates sites. In fact it is known that a lower energy value is not sufficient to reduce perceived noise annoyance. The drainage characteristic of these pavements has the advantage to ensure greater safety in case of rain even if it is subject to the loss of efficiency due to the occlusion of the pores over time. 

The main reasons to reuse the scrap tires and the recycled asphalt pavements are: 

  • to optimize the use of natural resources through the recovery and reuse of large quantities of waste and industrial by-products; 
  • to optimize the waste disposal reducing the amount of materials to be disposed of; 
  • to use the mechanical properties of the rubber within the bituminous materials to attenuate the mechanical vibrations and noise from road traffic; 
  • to identify recycling processes of used tires that are environmentally friendly and efficient from an energetic point of view; 
  • to evaluate the properties of particular industrial by-products to form a reinforcing element of bitumen to be used as a valid alternative to the process of modifying bitumen; 
  • the temperature decrease in mixing and laying phases has the advantage of reducing the levels of air pollution in urban areas compared to particular health impact of pollutants such as PAHs and also compared to the risk of exposed workers. 

It is estimated that in Italy each year, more than 350.000 tons of End-of-Life Tyres (ELT) are produced, and more than 70% are managed by ECOPNEUS: whenever all the rubber from ELT would have been used for asphalts, 19.000 km of roads could be paved, recycling and obtaining noise improvements. 

Low Noise Pavements (LNPs) are an interesting and economical solution where traffic noise reduction is necessary; rolling noise emissions are for cars already predominant at very low speeds (30-40 km/h) (Meiarashi, S., F. Nakashiba, H. Niimi, M. Hasebe, and T. Nakatsuji. Quantitative comparison between noise reduction factors of drainage asphalt pavement. Applied Acoustic, Vol. 44, No. 2, 1995, pp. 165- 179.). 

The present project deals with only a part of LNP types that is the family of in-plant produced warm asphalt mixes which can be paved with nominal layer thickness ranging between 10 and 50 mm. 

In order to investigate the effect of mixture composition on rolling noise, the tire-road noise generation must be considered. Texture and acoustic absorption are the pavement surface characteristics which play a fundamental role in the generation of rolling noise.

 

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As far as texture is regarding, there are several studies that have determined texture indicators for rolling noise assessment. As such studies did not define a clear relation between texture spectral indicators and mix composition, they do not allow to optimize the mixture composition to reduce rolling noise. 

As far as acoustical absorption is concerned, the maximum acoustical efficiency of surfaces is obtained with mixes characterized by high porosity, generally above 20%, and by a pore geometry that allows to optimize the spectrum of the acoustic absorption coefficient in order to obtain the maximum absorption at frequencies where the noise emissions are higher. From this point of view the project is aimed at showing the use of such asphalt pavements in order to provide authorities and designers of transport infrastructures with alternative and reliable devices to produce mixtures for low noise layers without compromising mechanical performance and adhesion levels. They will be produced by using the warm mix technology and composed by recycled asphalt pavements and crumb rubber from scrap tires: this leads to obtain a real energy saving, the reduction of polluting emissions as compared to the traditional techniques and the reduction of waste disposals; the use of recycled materials allows to save the use of non-renewable resources in asphalt pavement industry. 

Different studies demonstrated that applying the standard monitoring techniques is not enough to establish reliable results and different surfaces are not easily comparable. Therefore, new measurement protocols and methods have to be developed from standard ones in order to provide institutions with data of reliable monitoring campaigns. Moreover, there are few experiences in which the effects of mitigation measures (and even less on asphalts) have been tested against people perception. Therefore the projects also aims to provide new guidelines and templates for new measurements methods including psychoacoustical indicators. In fact, the project aims to developing new asphalts not only able to reduce noise level but also suitable to improve perceived noise: it has been demonstrated that at the same level different distribution of frequencies can change annoyance in exposed people.