| 1. |
- Forssén, Jens, et al.
(författare)
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A model of sound scattering by atmospheric turbulence for use in noise mapping calculations
- 2014
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Ingår i: Acta Acoustica united with Acustica. - : S. Hirzel Verlag. - 1610-1928 .- 1861-9959. ; 100:5, s. 810-815
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Tidskriftsartikel (refereegranskat)abstract
- Sound scattering due to atmospheric turbulence limits the noise reduction in shielded areas. An engineering model is presented, aimed to predict the scattered level for general noise mapping purposes including sound propagation between urban canyons. Energy based single scattering for homogeneous and isotropic turbulence following the Kolmogorov model is assumed as a starting point and a saturation based on the von Kármán model is used as a first-order multiple scattering approximation. For a single shielding obstacle the scattering model is used to calculate a large dataset as function of the effective height of the shielding obstacle and its distances to source and receiver. A parameterisation of the dataset is used when calculating the influence of single or double canyons, including standardised air attenuation rates as well as façade absorption and Fresnel weighting of the multiple façade reflections. Assuming a single point source, an aver aging over three receiver positions and that each ground reflection causes energy doubling, the final engineering model is formulated as a scattered level for a shielding building without canyon plus a correction term for the effect of a single or a double canyon, assuming a flat rooftop of the shielding building. Input parameters are, in addition to geometry and sound frequency, the strengths of velocity and temperature turbulence.
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| 2. |
- Hornikx, Maarten, 1980, et al.
(författare)
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Urban background noise mapping : The multiple-reflection correction term
- 2014
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Ingår i: Acta Acoustica united with Acustica. - 1610-1928 .- 1861-9959. ; 100:2, s. 293-305
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Tidskriftsartikel (refereegranskat)abstract
- Mapping of road traffic noise in urban areas according to standardized engineering calculation methods systematically results in an underestimation of noise levels at areas shielded from direct exposure to noise, such as inner yards. In most engineering methods, road traffic lanes are represented by point sources and noise levels are computed utilizing point-to-point propagation paths. For a better prediction of noise levels in shielded urban areas, an extension of engineering methods by an attenuation term Acan has been proposed, including multiple reflections of the urban environment both in the source and in the receiver area.The present work has two main contributions for the ease of computing Acan. Firstly, it is shown by numerical calculations that Acan may be divided into independent source and receiver environment terms, As and Ar. Based on an equivalent free field analogy, the distance dependence of these terms may moreover be expressed analytically. Secondly, an analytical expression is proposed to compute As and Ar for 3D configurations from using 2D configurations only. The expression includes dependence of the street width-to-height ratio, the difference in building heights and the percentage of facade openings in the horizontal plane. For the expression to be valid, the source should be separated from the receiver environment by at least four times the street width.
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| 3. |
- Meng, Xiang-hai, et al.
(författare)
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Safety evaluation of freeway basic segment based on CPMs and LOSS
- 2016
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Konferensbidrag (refereegranskat)abstract
- Safety evaluation of basic segments of freeway plays an important role in freeway safety management. Common methods for dividing basic segments were introduced and compared at first, and then a dynamic cluster segment division method was put forward based on where crashes located. Based on the numbers of crashes on divided segments, the statistical distribution of crashes was analyzed, and the result showed that the number of crashes on the divided segments followed the Negative Binomial (i.e., NB) distribution. Hence, Crash Prediction Models (i.e., CPMs) based on the NB distribution were established, and a method to evaluate the safety situation of freeway was proposed. Furthermore level of service of safety (i.e., LOSS) was introduced and the classification standard was determined, then a segment safety evaluation method based on LOSS was put forward. Both methods based on CPMs and based on LOSS were applied to the Jingzhu freeway, and the comparison showed that 57.8% segments were under the same level while the other were different. What’s more, it also could be find that the evaluation result based on CPM methods is more in line with actual situation. Safety evaluation method based on NB distribution considers traffic volume and geometric alignment, so it is more suitable for the freeway with complex geometric alignment conditions, mountainous freeway as Jingzhu freeway for instance. On the other hand, the safety evaluation method based on LOSS considers traffic volume and crash number, so it is more suitable for the freeway with good geometric alignment conditions.
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| 4. |
- Wei, Guang, et al.
(författare)
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Calibration of urban road network capacities
- 2022
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Ingår i: hEART 2022.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, a new calibration method for road capacities in urban networks is presented. The method relies on partial least squares (PLS) regression, which combines calibration and dimensionality reduction capabilities. A sampling strategy is implemented to further improve the calibration efficiency and accuracy. Moreover, influences of different parameters on calibration results are investigated. This method is demonstrated to be feasible and efficient in an urban road network (Stockholm, Sweden).
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| 5. |
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| 6. |
- Wei, Weigang, et al.
(författare)
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Urban background noise mapping : The general model
- 2014
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Ingår i: Acta Acoustica united with Acustica. - 1610-1928 .- 1861-9959. ; 100:6, s. 1098-1111
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Tidskriftsartikel (refereegranskat)abstract
- Surveys show that inhabitants of dwellings exposed to high noise levels benefit from having access to a quiet side. However, current practice in noise prediction often underestimates the noise levels at a shielded façade. Multiple reflections between façades in street canyons and inner yards are commonly neglected and façades are approximated as perfectly flat surfaces yielding only specular reflection. In addition, sources at distances much larger than normally taken into account in noise maps might still contribute significantly. Since one of the main reasons for this is computational burden, an efficient engineering model for the diffraction of the sound over the roof tops is proposed, which considers multiple reflections, variation in building height, canyon width, façade roughness and different roof shapes. The model is fitted on an extensive set of full-wave numerical calculations of canyon-to-canyon sound propagation with configurations matching the distribution of streets and building geometries in a typical historically grown European city. This model allows calculating the background noise in the shielded areas of a city, which could then efficiently be used to improve existing noise mapping calculations. The model was validated by comparison to long-term measurements at 9 building façades whereof 3 were at inner yards in the city of Ghent, Belgium. At shielded façades, a strong improvement in prediction accuracy is obtained.
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| 7. |
- Yew Wei, Joshua Ng, et al.
(författare)
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An assessment on the effectiveness of traffic calming markings and alternative for speed regulating strips
- 2013
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Ingår i: Proceedings of the 16th International Conference Road Safety on Four Continents. - Linköping : Statens väg- och transportforskningsinstitut.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The objective of this study is to evaluate the effectiveness of placing Traffic Calming Markings(TrCM) at different locations along the road to influence motorists’ speed, and provide an alternative to replace existing speed regulating strips on our roads. The study tested on 11 TrCM locations and the 85th percentile speed results showed that eight out of the 11 locations showed a reduction in speed while two locations have become ineffective and one location showed no change in speed. The results also indicated that TrCM was more effective when combined with other natural features such as a crest, a gentle bend or presence of a narrowing effect. However, it was less effective when applied along neutral road gradients and down slopes.With this in mind, further tests were carried out to compare the effectiveness of TrCM before and along a bend. Concurrently, similar arrangement was also carried out to determine the speed for Speed Regulating Strips (SRS) before and along a bend as a means to compare the effectiveness between the two traffic calming measures. Thereafter, the findings on both of these speed tests would ascertain the appropriate locations to provide TrCM to reduce motorists’ speed and an option to replace SRS if necessary.
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| 8. |
- Zhu, Li-wei, et al.
(författare)
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Fault Diagnosis On The Highway Surveillance And Control System Based On Petri Net Model
- 2013
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Ingår i: Proceedings of the 16th International Conference Road Safety on Four Continents. - Linköping : Statens väg- och transportforskningsinstitut.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Highway Surveillance and Control System (HSCS) is the critical system to improving the traffic safety and efficiency of highway. In this paper, the fault diagnosis model of HSCS based on Petri Net Model is provided in line with the composition, fault types and features of HSCS, and subsequently the fault diagnostic algorithm is given. In the end of this paper, the fault diagnosis of Microwave Vehicle Detector (MVD) in HSCS is presented to verifying the proposed fault diagnosis model and algorithm.
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