Abstract
Road traffic noise is one of the most relevant sources in the environmental noise pollution of the urban areas where dynamics of the traffic flow are much more complicated than uninterrupted traffic flows. It is evident that different traffic conditions would play the role in the urban traffic flow considering the dynamic nature of the traffic flow on one hand and presence of traffic lights, roundabouts, etc. on the other hand. The main aim of the current paper is to investigate the effect of different traffic conditions on urban road traffic noise. To do so, different traffic conditions have been theoretically generated by the Monte Carlo Simulation technique following the distribution of traffic speed in the urban roads. The “ASJ RTN-Model” has been considered as a base road traffic noise prediction model which would deal with different traffic conditions including steady and nonsteady traffic flow that would cover the urban traffic flow conditions properly. Having generated the vehicles speeds in different traffic conditions, the emitted noise (LWA) and subsequently the noise level at receiver (LA) were estimated by “ASJ RTN-Model.” Having estimated LWA and LA for each and every vehicle in each traffic condition and taking the concept of transient noise into account, the single event sound exposure levels (SEL) in different traffic conditions are calculated and compared to each other. The results showed that decelerated traffic flow had the lowest contribution, compared to congestion, accelerated flow, free flow, oversaturated congestion, and undersaturated flow by 16%, 14%, 12%, 12%, and 10%, respectively. Moreover, the distribution of emitted noise and noise level at receiver were compared in different traffic conditions. The results showed that traffic congestion had considerably the maximum peak compared to other traffic conditions which would highlight the importance of the range of generated noise in different traffic conditions.
Highlights
Industrialized living style of modern societies has produced a dramatic impact on the environment [1]
Environmental noise exposure is associated with annoyance [9, 10], sleep disturbance [11], cognitive ability in schoolchildren [12], and health impacts, especially cardiovascular conditions [13]
Having estimated the noise emitted by running vehicles in different traffic conditions, LWA (dB(A)), the noise level at receiver considering 20 (m) distance, LA (dB(A)), is calculated based on (6)
Summary
Industrialized living style of modern societies has produced a dramatic impact on the environment [1]. The environment noise and emission [2] have become a worldwide problem and the environmental impact control is one of the most important problems in the urban areas [3]. It is reasonable to affirm that, in urban areas, road traffic noise is the most relevant source [4] since airports are usually placed outside the downtowns and railways are usually designed to move out from the center of the cities [5] and rarely cross the residential districts [6]. In urban areas, the concentration of both road networks and city dwellers makes of traffic flow the main culprit of noise annoyance, which has to be precisely estimated and treated through relevant road traffic mitigation [7]. According to the WHO, the environment noise costs societies 0.2%-2.0% of the gross domestic product [17]
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