Validation of a complex urban noise model close to a road

The adequacy of a model for the sound level close to a road is investigated by comparing resulting predictions for the sound level over a building façade with measurements. The road model involves the road geometry (the number and positions of traffic lanes), the traffic structure (vehicle flow rates and their average speeds in each lane) and equivalent omnidirectional point sources representing the vehicles. It is found that the assumed road traffic noise source model is adequate only for predicting levels over the higher part of the façade. However the investigation has allowed definition of what improvements are needed in the road source modelling to enable adequate predictions over the whole of the building façade.     

Prediction and Limitations of Noise Maps Developed for Heterogeneous Urban Road Traffic Condition: A Case Study of Surat City,India

Road traffic noise pollution has been recognized as a serious issue which affects human health as well as affects urban regions. Noise maps are very beneficial to identify the impact of noise pollution. A noise mapping study performed to study the propagation of noise in tier-II city along with field measurements. The noise maps are developed using a computer simulation model (SoundPLAN essential 4.0 software). The noise prediction models like U.K’s CoRTN, Germany’s RLS-90, and their modified versions, which can be used for homogenous road traffic conditions, cannot be successfully applied in heterogeneous road traffic conditions of India. In developing country like India, road traffic noise pollution depends on the composition of heterogeneous traffic volume, variance in road geometrical, honking conditions, un-authorized parking, and varying density of the building on either side of the road. These traffic compositions contain vehicles, which have different sizes, speeds variations, a different dimension of vehicles. Because of fluctuating speeds, lack of lane disciplines, and un-authorized parking on main road lanes, honking events becomes inevitable, which changes and affects the urban soundscape of nations like India. Analysis of noise maps showed that horn honking due to un-authorized parked vehicles contributed an additional increase up to 11 dB (A) noise, which is quite significant.     

公路交通噪声等效车道距离的确定方法探讨

在公路交通噪声计算中,目前常用的确定等效车道距离的方法是计算接受点至近车道和远车道的距离的几何平均值,但使用该方法得到的接受点处的交通噪声与使用两个车道分别计算后再叠加的方法所得到结果相比,存在一定偏差。本文提出用调和平均值确定等效车道距离,即用接受点至近车道和远车道的距离的几何平均值的平方除以算术平均值来确定等效车道距离。通过比较,证明调和平均法比几何平均法具有更高的精确性。     

Influence of vehicle noise emission directivity on sound level distribution in a canyon street. Part II: Experimental verification

In the paper, predictions of relative sound level distribution on building façades in city-centres obtained by using the simulation PROP11 program are compared with measurements. The simulation involves the geometry of surrounding buildings, road geometry (number of lanes and their positions) and traffic structure (vehicle flow rates and their average speeds). The agreement between measurement and simulation results is tested for different directivity characteristics of an equivalent point source representing the vehicles.     

Traffic noise reduction due to the porous road surface

Porous road surfaces reduce road traffic noise. A new method of noise reduction assessment is proposed. The noise generated by a few vehicles was measured two times: on an old surface with the dense asphalt and on a new surface with the porous asphalt. Subjective assessments of drive-by noise suggest that the sound exposure and the road surface coefficient can be used as the acoustical characteristics of a road surface. Their average values, with the average number of vehicles passing the receiver during a day or night, makes it possible to predict the equivalent continuous A-weighted sound pressure level for the new road surface. This is the main objective of this paper.     

Development of a highway traffic noise prediction model that considers various road surface types

A highway traffic noise prediction model has been developed for environmental assessment in South Korea. The model is based on an outdoor sound propagation method and is fully compliant with ISO 9613 and the sound power level (PWL) estimation for a road segment, as suggested in the ASJ Model-1998 that is based on PWLs. Due to that model’s selection of two pavement types, such as asphalt or concrete pavement, an unacceptable traffic noise prediction is made in cases where the road surface is different from that on which the model is based. In order to address this problem, several road surface types are categorized, and the PWL of each surface type is determined and modeled by measuring the noise levels obtained from newly developed methods. An evaluation of the traffic noise prediction model using field measurements finds good agreement between predicted and measured noise levels.     

Effect of the lane reduction in the cellular automata models applied to the two-lane traffic

More investigated situations in the field of traffic modelling are those of traffic bottlenecks caused by slow vehicles or road defects. The new aspect of this paper is the simulation of vehicular dynamics near a partial reduction in a road from two lanes to one lane. In order to reduce the bad impact of waiting vehicles behind the defect region, a strategy regulating the vehicle movement in the vicinity of the reduced lane is taken into account. The simulation model is based on the cellular automata model of Nagel–Schreckenberg with additional rules of lane change. The partial lane reduction strongly reduces the road capacity, and the added regulation strategy leads to a more interesting shape of the fundamental diagram, which depends on different constraints on the model parameters, e.g., the length of the reduced lane, the maximal speed, and the length of the connection sites near the entry of the reduced lane.     

等效道路线声源位置优化研究

计算道路交通噪声时,一般将每个车道等效为1个线声源。有时,为了简化计算,将道路等效为1个线声源,等效线声源位置为道路中轴;或等效为2个线声源,等效线声源位置为道路两侧中心线或两侧最外车道中心线。推导不同等效方法下观测点噪声的计算公式,并探讨不同等效方法引起的误差。研究结果表明,将道路等效为2个线声源,等效线声源位置为道路两侧中心线的简化方法引起的误差最小。     

Determination of the sound power levels emitted by various vehicles using a novel testing method

This paper presents a new and efficient method to determine sound power levels (PWLs). PWLs, generally used for modeling outdoor sound simulations, are obtained from sounds that are emitted by various types of vehicles and cause road traffic noise. Other models, such as HARMONOISE and the ASJ Model, are also based on PWLs. However, a more efficient method is required for determining PWLs from sound pressure levels (SPLs) that typically are measured by field testing and evaluating the influence of different vehicles and road surfaces. The statistical pass-by (SPB) of ISO 11819-1 is used for SPL measurements; however, numerous SPBs must be carried out to reduce measurement uncertainty as well as to satisfy requirements related to meteorological conditions and background noise. In order to alleviate this problem and to make the determination of PWLS more efficient, a testing approach is presented that uses both the novel close proximity (NCPX) method and the pass-by method to determine PWLs.     

道路交通的流体物理模型与粒子仿真方法

针对受多种因素影响的复杂道路交通系统问题,基于颗粒动力学理论,结合传统的Lighthill-WhithamRichards物理模型,建立道路交通系统的流体物理模型,采用无网格粒子与网格相结合的方法进行数值仿真,并应用于典型道路交通问题的求解.在新模型中,将车辆比拟为硬颗粒,车辆的跟车比拟为颗粒间的碰撞相互作用,已知道路情况对驾驶员操作车辆的影响比拟为流-粒两相系统中的外部流体驱动力作用,不同车道间车辆的影响比拟为颗粒间的黏性作用,从而在颗粒动力学理论的基础上,推导建立了道路交通系统拟流体模型;引入光滑离散颗粒流体动力学(SDPH)对车辆系统模型进行离散,建立"SDPH车辆"与真实车辆之间的一一对应关系,再结合有限体积方法,对道路交通构建的双流体模型进行求解,建立求解交通流体物理模型的新型仿真方法.最后,采用所建立的模型和方法对车辆汇入以及机非混合对交通系统的影响过程进行了数值仿真,所得结果与实测值符合较好,表明新的模型和方法有效性好、可靠性高,为道路交通问题的解决提供了一条全新的途径.     

Honking noise corrections for traffic noise prediction models in heterogeneous traffic conditions like India

In developing countries like India, the nature of the composition of traffic is heterogeneous. A heterogeneous traffic flow consists of vehicles that have different sizes, speeds, vehicle spacing and operating characteristics. As a result of the widely varying speeds, vehicular dimensions, lack of lane disciplines, honking becomes inevitable. In addition, it changes the urban soundscape of developing countries. In heterogeneous traffic conditions, horn events increase noise level (L_den) by 0.5–13 dB(A) as compared to homogenous traffic conditions. Therefore, the traffic prediction models that are used for homogenous traffic conditions are not applicable in heterogeneous traffic conditions. To increase the accuracy of noise prediction models, in depth understanding of heterogeneous traffic noise is required. Understanding the real traffic noise characteristics requires quantification of some of the basic traffic flow characteristics such as speed, flow, Level Of Service (LOS) and density. In a given roadway, the noise level changes with density and LOS on the road. In this paper, a new factor for horn correction is introduced with respect of Level Of Service (LOS). The horn correction values can be incorporated in traffic noise models such as CRTN, FHWA, and RLS 90, while evaluating heterogeneous traffic conditions.     

A quantum mechanics-based approach to model incident-induced dynamic driver behavior

A better understanding of the psychological factors influencing drivers, and the resulting driving behavior responding to incident-induced lane traffic phenomena while passing by an incident site is vital to the improvement of road safety. This paper presents a microscopic driver behavior model to explain the dynamics of the instantaneous driver decision process under lane-blocking incidents on adjacent lanes. The proposed conceptual framework decomposes the corresponding driver decision process into three sequential phases: (1) initial stimulus, (2) glancing-around car-following, and (3) incident-induced driving behavior. The theorem of quantum mechanics in optical flows is applied in the first phase to explain the motion-related perceptual phenomena while vehicles approach the incident site in adjacent lanes, followed by the incorporation of the effect of quantum optical flows in modeling the induced glancing-around car-following behavior in the second phase. Then, an incident-induced driving behavior model is formulated to reproduce the dynamics of driver behavior conducted in the process of passing by an incident site in the adjacent lanes. Numerical results of model tests using video-based incident data indicate the validity of the proposed traffic behavior model in analyzing the incident-induced lane traffic phenomena. It is also expected that such a proposed quantum-mechanics based methodology can throw more light if applied to driver psychology and response in anomalous traffic environments in order to improve road safety.     

The annual average sound level of road traffic noise estimated from the speed-flow diagram

The speed-flow diagram correlates traffic speed and traffic flow on a road. The presented method enables estimation of the annual average sound level of the road traffic noise when the characteristics of the diagram are available: traffic flow capacity, free traffic speed, and traffic capacity speed (Fig. 1). Bunches of vehicles decrease the traffic speed and traffic noise.     

Property prices in urban areas affected by road traffic noise

This paper reports a revealed preference study into the different effects of road traffic noise on property values in residential areas with similarly high road traffic sound levels but with what appear to be important differences in the market for different types of residential property in each area. The results show significant differences in the revealed effects of noise on property prices between the three areas with in one case an increasing (and possibly misleading) relationship between higher monetary values and higher sound levels. A number of possible explanations for the findings are discussed in the paper.     

A new traffic model with the consideration of coupling effect with two lanes

This paper introduces a new two-lane high-order continuum model by embedding the two delay time scales continuum traffic model presented by Xue (2003 Phys. Rev. E 68 066123) into the multi-lane model proposed by Daganzo (1997 Transpn. Res. B 31 83) with the consideration of the coupling effect between the vehicles of two lanes in instantaneous traffic situation and lane-change effect. In the novel model, the coupling effect of two lanes and phenomena of lane change, which were not discussed in Daganzo's model and Xue's model, are taken into account. Numerical simulation shows that it is in accordance with real traffic flow. This obviously indicates that the new phenomenon and behaviour are analogous results as single lane presented by Xue, and the proposed model is more reasonable on two lanes. Furthermore, the generation rate between two lanes is also investigated. The results show that the formation and diffusion of traffic shock wave can be better simulated on two lanes.     

Analysis of the wave properties of a new two-lane continuum model with the coupling effect

A multilane extension of the single-lane anisotropic continuum model (GK model) developed by Gupta and Katiyar for traffic flow is discussed with the consideration of the coupling effect between the vehicles of different lanes in the instantaneous traffic situation and the lane-changing effect. The conditions for securing the linear stability of the new model are presented. The shock and the rarefaction waves, the local cluster effect and the phase transition are investigated through simulation experiments with the new model and are found to be consistent with the diverse nonlinear dynamical phenomena observed in a real traffic flow. The analysis also focuses on empirically observed two-lane phenomena, such as lane usage inversion and the density dependence of the number of lane changes. It is shown that single-lane dynamics can be extended to multilane cases without changing the basic properties of the single-lane model. The results show that the new multilane model is capable of explaining some particular traffic phenomena and is in accordance with real traffic flow.     

Road traffic noise prediction based on speed-flow diagram

The method enables calculation of the annual average sound level of the road traffic noise, when the characteristics of the speed-flow diagram are available: the average speed of freely cruising vehicles, capacity of the traffic flow, traffic speed at the traffic flow capacity, and the slope of the decreasing traffic speed versus traffic flow. Under any conditions, traffic congestion reduces the annual average sound level. The final conclusion is that strong traffic congestion cannot be ignored in noise prediction.     

A road traffic noise pattern simulation model that includes distributions of vehicle sound power levels

Annoyance, sleep disturbance and other health effects of road traffic noise exposure may be related to both level and number of noise events caused by traffic, not just to energy equivalent measures of exposure. Dynamic traffic noise prediction models that include instantaneous vehicle noise emissions can be used to estimate either of these measures. However, current state-of-the-art vehicle noise emission models typically consider a single emission law for each vehicle category, whereas measurements show that the variation in noise emission between vehicles within the same category can be considerable. It is essential that the influence of vehicles that are producing significantly more (or less) noise than the average vehicle are taken into account in modeling in order to correctly predict the levels and frequency of occurrence of road traffic noise events, and in particular to calculate indicators that characterize these noise events. Here, an approach for predicting instantaneous sound levels caused by road traffic is presented, which takes into account measured distributions of sound power levels produced by individual vehicles. For the setting of a receiver adjacent to a dual-lane road carrying free flow traffic, the effect of this approach on estimated percentile levels and sound event indicators is investigated.     

Vehicular motion in counter traffic flow through a series of signals controlled by a phase shift

We study the dynamical behavior of counter traffic flow through a sequence of signals (traffic lights) controlled by a phase shift. There are two lanes for the counter traffic flow: the first lane is for east-bound vehicles and the second lane is for west-bound vehicles. The green-wave strategy is studied in the counter traffic flow where the phase shift of signals in the second lane has opposite sign to that in the first lane. A nonlinear dynamic model of the vehicular motion is presented by nonlinear maps at a low density. There is a distinct difference between the traffic flow in the first lane and that in the second lane. The counter traffic flow exhibits very complex behavior on varying the cycle time, the phase difference, and the split. Also, the fundamental diagram is derived by the use of the cellular automaton (CA) model. The dependence of east-bound and west-bound vehicles on cycle time, phase difference, and density is clarified.