Effect of traffic noise on perceived visual impact of motorway traffic

Visual impact is one of the major environmental impacts of motorways and requires adequate assessment. This study investigated the effect of traffic noise on the perceived visual impact of motorway traffic by comparing impact with sound to impact without sound. Computer visualisation and edited audio recordings were used to simulate different traffic and landscape scenarios, varying in four traffic conditions, two types of landscape, and three viewing distances. Subjective visual judgments on the simulated scenes with and without sound were obtained in a laboratory experiment. The results show that motorway traffic induced significant visual impact. In both sound conditions, increases in traffic volume led to higher visual impact and changes in traffic composition changed the impact significantly when traffic flow was low. Visual impact was significantly higher in the natural landscape and the increment was largely constant and independent from the effect of traffic condition in both sound conditions. The effect of viewing distance was also significant and there was a rapid-to-gentle decrease of visual impact by distance both with and without sound, but the decrease with sound was less rapid and the decrease pattern less clear. Overall, introduction of traffic noise increased the visual impact by a largely constant level which did not show clear dependence with noise level, traffic condition, landscape type, or viewing distance, although there was a possible effect of viewing distance on the increase. It suggests that the additional impact caused by traffic noise should be considered in visual impact assessment of motorway projects

Prediction of the visual impact of motorways using GIS

Large scale transportation projects can adversely affect the visual perception of environmental quality and require adequate visual impact assessment. In this study, we investigated the effects of the characteristics of the road project and the character of the existing landscape on the perceived visual impact of motorways, and developed a GIS-based prediction model based on the findings. An online survey using computer-visualised scenes of different motorway and landscape scenarios was carried out to obtain perception-based judgements on the visual impact. Motorway scenarios simulated included the baseline scenario without road, original motorway, motorways with timber noise barriers, transparent noise barriers and tree screen; different landscape scenarios were created by changing land cover of buildings and trees in three distance zones. The landscape content of each scene was measured in GIS. The result shows that presence of a motorway especially with the timber barrier significantly decreases the visual quality of the view. The resulted visual impact tends to be lower where it is less visually pleasant with more buildings in the view, and can be slightly reduced by the visual absorption effect of the scattered trees between the motorway and the viewpoint. Based on the survey result, eleven predictors were identified for the visual impact prediction model which was applied in GIS to generate maps of visual impact of motorways in different scenarios. The proposed prediction model can be used to achieve efficient and reliable assessment of visual impact of motorways

Combined acoustical and visual performance of noise barriers in mitigating the environmental impact of motorways.

This study investigated the overall performance of noise barriers in mitigating environmental impact of motorways, taking into consideration their effects on reducing noise and visual intrusions of moving traffic, but also potentially inducing visual impact themselves. A laboratory experiment was carried out, using computer-visualised video scenes and motorway traffic noise recordings to present experimental scenarios covering two traffic levels, two distances of receiver to road, two types of background landscape, and five barrier conditions including motorway only, motorway with tree belt, motorways with 3 m timber barrier, 5 m timber barrier, and 5 m transparent barrier. Responses from 30 participants of university students were gathered and perceived barrier performance analysed. The results show that noise barriers were always beneficial in mitigating environmental impact of motorways, or made no significant changes in environmental quality when the impact of motorways was low. Overall, barriers only offered similar mitigation effect as compared to tree belt, but showed some potential to be more advantageous when traffic level went high. 5 m timber barrier tended to perform better than the 3 m one at the distance of 300 m but not at 100 m possibly due to its negative visual effect when getting closer. The transparent barrier did not perform much differently from the timber barriers but tended to be the least effective in most scenarios. Some low positive correlations were found between aesthetic preference for barriers and environmental impact reduction by the barriers

Perceived integrated impact of visual intrusion and noise of motorways: Influential factors and impact indicators

Motorways are often seen as intrusive to both landscape and soundscape, and recent studies on multisensory perception suggest that an integrated assessment of the environmental impacts is necessary. This paper investigates the effects of traffic condition, distance to road and background landscape on the perceived integrated impact of noise and visual intrusion of motorways, and explores if noise exposure can be a powerful indicator for the perceived integrated impact. Six traffic conditions, consisting of three levels of noise emission × two levels of heavy good vehicle percentage in traffic composition, two types of background landscape and three distances to road, were designed as experimental scenarios, and created using computer visualisation and edited audio recordings. A laboratory experiment was carried out to obtain ratings of perceived environmental quality of each experimental scenario. The results show that traffic volume as expressed by noise emission level strongly influenced the perceived integrated impact, whereas traffic composition did not make noticeable differences. Distance to road was the second most influential factor, followed by background landscape. A regression model using noise level at receiver position and type of background landscape as independent variables was developed and can explain about a quarter of the variation in the perceived integrated impact

When is enough, enough? Identifying predictors of capacity estimates for onshore wind-power development in a region of the UK

The level of ‘wind-prospecting’ presently occurring in the UK is increasing the likelihood that new wind-power developments will conflict with other existing and/or proposed schemes. This study reports multiple-regression analyses performed on survey data obtained in a region of the UK (i.e. Humberhead Levels, near Doncaster) simultaneously subject to nine wind-farm proposals (September 2008). The aim of the analysis was to identify which survey-items were predictors of respondents' estimates of the number of wind turbines they believed the region could reasonably support (i.e. capacity estimates). The results revealed that the majority of respondents would endorse some local development; however, there was substantial variability in the upper level that was considered acceptable. Prominent predictors included general attitude, perceived knowledge of wind power, community attachment, environmental values, visual attractiveness of wind turbines, and issues relating to perceived fairness and equity. The results have implications for Cumulative Effects Assessment (CEA) – and in particular the assessment of Cumulative Landscape and Visual Impacts (CLVI) – and support calls for greater community involvement in decisions regarding proposed schemes

In search for multifunctionality. The contribution of scenic landscape assessment

The attention recently paid to ecosystem services, which include cultural services, such as spiritual and aes-thetic experiences, seems to encourage the consideration of landscape scenic values into rural development policies. However, existing theoretical frameworks doesn't clarify enough the differences between various landscape services, among which potential conflicts - deriving from multiple values related to the same spatial assets - may arise. A sound assessment of landscape services is necessary. The chapter aims to show that multifunctionality is a goal-oriented concept and an option, non to be considered an intrinsic character of landscape policies. Rural, environmental, landscape and spatial policies can partially share certain strategic objectives, spatial targets, and evaluation frameworks. The paper illustrates existing techniques (as well as original proposals) for supporting landscape and rural policies through scenic landscape assessment, particularly: detailing categories of cultural services related to landscape amenity and developing scenic landscape indicators for environmental assessment frameworks. The second part of the chapter illustrates methodologies for the assessment of scenic landscape, their application in spatial planning and their potential application in rural policies, based on the Authors' research experiences on cultural landscapes in Italy. Evidence gained through the cases studies indicates that landscape scenic beauty can be protected and enhanced by integrating landscape and rural policies. The paper drafts a theoretical framework and illustrates the practical outcomes by a wide range of possible planning measure