Vegetation of road verges on an urbanisation gradient in Potchefstroom, South Africa

A vegetation survey of road verges along an urban to rural gradient in the Potchefstroom Municipal Area was conducted. Important applications of these studies include understanding of the role of indigenous (native) and exotic species in the overall synanthropisation of vegetation. The present study forms part of a research programme on spontaneous vegetation in urban open spaces in the North-West Province of South Africa. A numerical classification technique ( ) was used as a first approximation and the classification was refined using Braun-Blanquet procedures. The result is a phytosociological table from which 13 plant communities and seven sub-communities were recognised. Although some of these communities and sub-communities are similar to previously described vegetation types in natural and disturbed areas, most of them were not described before in South Africa. Two ordination scatter diagrams show the distribution of the plant communities along gradients which were related to the depth of the soil water table, habitat type, trampling, soil compaction and percentage of gravel in the soil surface. Similarities between roadside vegetation in this study and those overseas are discussed, as well as the possible role of road verges as dispersal corridors between natural and disturbed areas.     

Spatial and temporal variations in Pb concentrations and isotopic composition in road dust, farmland soil and vegetation in proximity to roads since cessation of use of leaded petrol in the UK

Results are presented for a study of spatial distributions and temporal trends in concentrations of lead (Pb) from different sources in soil and vegetation of an arable farm in central Scotland in the decade since the use of leaded petrol was terminated. Isotopic analyses revealed that in all of the samples analysed, the Pb conformed to a binary mixture of petrol Pb and Pb from industrial or indigenous geological sources and that locally enhanced levels of petrol Pb were restricted to within 10 m of a motorway and 3 m of a minor road. Overall, the dominant source of Pb was historical emissions from nearby industrial areas. There was no discernible change in concentration or isotopic composition of Pb in surface soil or vegetation over the decade since the ban on the sale of leaded petrol. There was an order of magnitude decrease in Pb concentrations in road dust over the study period, but petrol Pb persisted at up to 43% of the total Pb concentration in 2010. Similar concentrations and spatial distributions of petrol Pb and non petrol Pb in vegetation in both 2001 and 2010, with enhanced concentrations near roads, suggested that redistribution of previously deposited material has operated continuously over that period, maintaining a transfer pathway of Pb into the biosphere. The results for vegetation and soil transects near minor roads provided evidence of a non petrol Pb source associated with roads/traffic, but surface soil samples from the vicinity of a motorway failed to show evidence of such a source.     

衢州农村公路路堑水毁原因分析及预防措施

通过对衢州市农村公路水毁调查,分析了农村公路路堑水毁的影响因素,主要是降水、土体性质、边坡形态、植被等,并结合衢州农村特色提出了预防措施,使农村公路越来越完善。     

浅谈混凝土道路施工工艺

对混凝土道路的施工工艺进行了介绍，分别对路基工程、天然砂砾垫层、水泥稳定碎石基层及混凝土路面的工艺流程和操作步骤作了具体阐述，以确保混凝土道路工程质量。     

Environmental exposure of road borders to zinc

The emissions of zinc along roads originating from tyre wear, corrosion of safety fence and other traffic-related sources have been quantified and validated by measured long-term loads in road run-off and airborne solids (drift) for 29 published case studies. The distribution pattern over the road border at various distances from the edge of the paved surface is assessed on the basis of 38 published case studies with measured concentrations in soil. For the impact assessment, the road border is differentiated into a zone that is part of the "technosphere" and the "target zone" beyond that technosphere that can be considered as part of the receiving environment. The "technosphere" of the road includes the central reservation, the hard and the soft shoulder or, if one or both shoulders are not present, the so-called obstacle "free zone" that is defined by road engineers. Pollution within the technosphere may require appropriate management of solid disposal and isolation from groundwater to prevent further distribution of pollutants to the environment. In the target zone along regional roads, the zinc load is about 4 mg/m(2) year and this is of the same order of magnitude as that of atmospheric deposition in areas beyond the influence of roads (background). In the target zone along highways, the zinc load is increased in comparison to the background deposition. The average load of about 38 mg/m(2) year is similar to that in fertilised agricultural land. Because most of the emitted zinc stays in the technosphere, the total amount entering this target zone along highways is limited. From the 140 tons of zinc per year that is released from tyre wear in The Netherlands, 64 tons is emitted in the urban area, 6.5 tons reaches to the target zones of all roads and only 1.1 tons of zinc will enter the target zone along highways. This amount will be further decreased by the application of porous asphalt in the near future. The emission from safety fence corrosion does not enter the target zone. Only in special cases, such as bridges, crossings and squares the release of zinc from these sources may enter the aquatic environment by the discharge of run-off.     

Cliff roads: An ecological conservation technique for road construction in mountainous regions of China

Cliff ecosystems are important for biodiversity protection because these sites often support surprisingly ancient and diverse communities, including rare plants and lichens, trees, birds, and small mammals. To protect Chinese cliff ecosystems, an ancient cliff road construction technique is now being used. To understand the environmental benefits of this approach, we monitored eight cliff road sites in the warm Shennongjia region of China's Hubei Province from June 2006 to July 2009 during road construction. Compared with the traditional filling in of roadside slopes or bridge construction formerly used for highway construction in this area, the cliff highway technique, which combines cantilevered slab roads along the edge of the cliff with bridge support structures where additional support is required, reduces environmental damage and represents a good option for the conservation of fragile cliff ecosystems, while greatly reducing the construction cost. In such areas, the basic objectives of road construction must include biodiversity protection and careful control of the construction process and subsequent cleanup of the site, which cannot be ignored as a result of concentrating on the goal of using the roads to promote regional economic and tourism development.     

Edge effects of roads on temperature, light, canopy cover, and canopy height in laurel and pine forests (Tenerife, Canary Islands)

The estimation of the road edge effect is useful to understand changes induced by the road network on ecosystems. Road networks on islands may break ecosystem integrity through microclimate edge effects, which are known to be associated with disturbances to animal and plant communities. Road edge effects have been scarcely studied on oceanic islands. In this paper we studied road edge effects on microclimate and canopy structure in laurel and pine forests in Tenerife (Canary Islands). We assessed depth of road edge effect for temperature at four vertical layers (soil, litter and air at 5 cm and 1.3 m above ground), light intensity, canopy cover and height, in transects running from narrow (6–7 m width) asphalt roads and dust trails to 100 m to the interior of both forests. We used an ANOVA procedure with Helmert difference contrasts to identify the distances along transects over which edge effects were significant. We detected significant gradients for most parameters but they were consistently narrow both within and between forests. In the laurel forest, we detected highly significant gradients for soil temperature, light, and canopy cover and height in both asphalt and unpaved roads. In the pine forest, we detected a highly significant gradient for soil temperature at asphalt roads, and a significant light gradient for both asphalt and unpaved roads. From the road edge to the forest interior, significant temperature changes persisted for only 3 m, light variation persisted for 6 m, and canopy cover and height changed significantly within the first 10 m. Asphalt roads and dust trails revealed different patterns of variation for temperature between edge and interior. No differences were found between the two types of roads in edge-interior trends for light or canopy structure. The abruptness of microclimate and canopy gradients was slightly higher in the laurel forest than in the pine forest, caused by a higher edge contrast in the former. The depth of the road edge effect found in laurel and pine forests was small, but it could have cumulative effects on forest microclimate and forest associated biota at the island scale. Such changes deserve attention by local road managers for planning and design purposes.     

基于ENVI-met模型的北京市典型道路 行道树树种优化研究

城市道路是城市居民重要的活动场所,人行道空气质量与居民健康密切相关。行道树被广泛认为会降低道路空气交换速率,从而造成道路污染物浓度升高;然而,行道树通过改变湍流形成空气颗粒物浓度差异化分布,同时对颗粒物有一定截获能力。因此,合理规划行道树有望改变道路空气流场进而改善局部空气质量。以北京地安门内大街为例,从改善道路污染的角度展开基于ENVI-met模型的行道树设计与技术探索,得出:1)ENVI-met可用于道路污染物扩散及沉降模拟研究;2)行道树冠幅是影响道路颗粒物扩散的重要因素,冠幅宽度到达道路宽度时,往往会影响颗粒物的快速扩散,导致道路颗粒物浓度升高;3)冠幅较大且冠层高度靠近地面的行道树对道路颗粒物有较好的吸附效果。本研究为行道树树种选择提供有利依据,同时也是国内首次用ENVI-met对颗粒物扩散和沉降开展研究。     

黄土台塬区农村道路生态化模式建构 及设计应对探究——以宝鸡市金台区北坡 路域生态整治为例

农村道路生态化研究对统筹推进中国农村人居环境整治工作、维育区域生态格局乃至实施乡村振兴战略具有重要意义。针对当前中国黄土台塬区农村道路建设过程中景观割裂、环境侵扰和水土流失等问题,基于国内外道路生态学的理论和实践,梳理农村道路环境及景观研究进展,厘清其景观生态化内涵机理,从道路主体、沿线设施、路域环境、养护管理等多维度构建黄土台塬区农村道路景观生态化改造模式。以宝鸡市金台区北坡生态整治项目作为实证案例,总结梳理美丽农村路绿色化营建方法举措,通过生态修复、景观重构、文化塑造和工程建设等手段推进黄土台塬区农村路域景观生态的修复与重塑,为营建美丽绿色农村路、助力乡村振兴战略提供技术支撑。     

Rural road networks as barriers to gene flow for amphibians: Species-dependent mitigation by traffic calming

Population structuring based on mitochondrial DNA variation along the rural landscape of the Trubia valley in North Iberia revealed significant association between road density and genetic distance between populations of two amphibian species, the midwife toad Alytes obstetricans and the palmate newt Lissotriton helveticus. Traffic calming (concentration of flows on minor rural roads at a few highways to decrease volumes and speeds) near urban settlements mitigates the population fragmentation of L. helveticus but not that of A. obstetricans, indicating that even small roads with low-intensity traffic act as barriers for the latter species. We suggest that the construction of passages for amphibians across rural roads would potentially mitigate population fragmentation of endangered species like the anuran A. obstetricans.     

An Unmanned Aerial Vehicle‐Based Imaging System for 3D Measurement of Unpaved Road Surface Distresses1

Abstract: Road condition data are important in transportation management systems. Over the last decades, significant progress has been made and new approaches have been proposed for efficient collection of pavement condition data. However, the assessment of unpaved road conditions has been rarely addressed in transportation research. Unpaved roads constitute approximately 40% of the U.S. road network, and are the lifeline in rural areas. Thus, it is important for timely identification and rectification of deformation on such roads. This article introduces an innovative Unmanned Aerial Vehicle (UAV)‐based digital imaging system focusing on efficient collection of surface condition data over rural roads. In contrast to other approaches, aerial assessment is proposed by exploring aerial imagery acquired from an unpiloted platform to derive a three‐dimensional (3D) surface model over a road distress area for distress measurement. The system consists of a low‐cost model helicopter equipped with a digital camera, a Global Positioning System (GPS) receiver and an Inertial Navigation System (INS), and a geomagnetic sensor. A set of image processing algorithms has been developed for precise orientation of the acquired images, and generation of 3D road surface models and orthoimages, which allows for accurate measurement of the size and the dimension of the road surface distresses. The developed system has been tested over several test sites with roads of various surface distresses. The experiments show that the system is capable for providing 3D information of surface distresses for road condition assessment. Experiment results demonstrate that the system is very promising and provides high accuracy and reliable results. Evaluation of the system using 2D and 3D models with known dimensions shows that subcentimeter measurement accuracy is readily achieved. The comparison of the derived 3D information with the onsite manual measurements of the road distresses reveals differences of 0.50 cm, demonstrating the potential of the presented system for future practice.     

A wind-tunnel study on diffusion from urban major roads

We evaluate the performance of reduced-scale wind-tunnel experiments that simulate vehicle-induced pollutant diffusion in urban roadside area. From Japanese urban areas, we selected four sites that cover a wide range of road structures, building density, and roadside features. At each site, four field stations were installed to monitor concentration of air pollutants including nitrogen oxides (NOx). In the wind-tunnel experiments, ethane was emitted from along the major roads, and its concentration was compared with the background-subtracted field values. For annual average of NOx in the year 2006, we found that an appropriately normalized concentration agreed fairly well between wind-tunnel and field measurements. The wind-tunnel concentration distribution measured at a high spatial resolution revealed that roadside features such as tall buildings, noise barriers, and trees have considerable effect on the concentration on the downwind or upwind side of the roads. The high-resolution results are expected to serve as a useful database for evaluating numerical air pollution models.     

Anthropogenic platinum group element (Pt, Pd and Rh) concentrations in road dusts and roadside soils from Perth, Western Australia

The emission of platinum group elements (PGE) from automobile catalytic converters has led to rapid increases in Pt, Pd and Rh concentrations in roadside media. This article represents the first detailed study to assess PGE levels in road dusts and roadside soils in Australia. Road dust and roadside soil samples were analysed by ICP-MS following microwave digestion and cation exchange. All samples show elevation of PGE above average upper crust values, with maximum values of 420 ng g(-1) Pt, 440 ng g(-1) Pd and 91 ng g(-1) Rh. PGE ratios in road dusts and soils are consistent with known catalytic converter compositions and while Pt and Rh abundances are comparable with European studies, Pd levels are substantially higher in Australian samples. PGE in these samples are not correlated with Pb, though positive correlations with Ce, Cu and Y are evident. No straightforward relationship between traffic volume and PGE abundance is evident and factors such as driving style, topography, road drainage and potentially climate exert considerable influences.     

碎石桩在公路软基处理中的应用

对采用碎石桩处理的软基进行了分析,指出其在软土中可以起到加固、排水、减少沉降、提高地基承栽力的作用,结合JGJ79-2002建筑地基处理技术规范,介绍了碎石桩在公路软基加固中的应用及施工注意事项,以指导实践。     

Assessment of road instability along a typical mountainous road using GIS and aerial photos, Lebanon – eastern Mediterranean

The steeply sloping and mountainous nature of the Lebanese territory gives rise to a spectrum of natural hazards. It is a rugged area cut by a dense network of roads connecting scattered but highly populated cities. The roads experience heavy traffic. They often follow geological formations of weak lithologies and cross fault systems inducing recurrence of mass movements. When the rather poor road construction in Lebanon is added to this, the result is a potential risk to life as well as economic losses. The purpose of this study was to investigate the interactive components determining the hazards affecting the highway between Beirut and Broummana (Mount Lebanon). It specifically aims to show, with the aid of GIS and aerial photographs, the integration of datainput from those components for optimizing approaches to highway hazard analysis. Electronic Publication     

The impact of environmental factors on benthos communities and freshwater gastropod diversity in urban sinkhole ponds in roadside and forest contexts

Sinkhole ponds originated as a result of human activity leading to ground subsidence and create important habitats for the diversity of benthos fauna in urban areas. The objectives of this study were to determine whether the context (roadside/forest) is important in relation to the composition and diversity of macroinvertebrates, and to evaluate the influence of environmental factors (e.g. water quality) on snail communities. The study showed that the context of ponds had an impact on the properties of the water. Ponds located along roads were characterised by higher conductivity and a higher concentration of calcium and phosphates. The fauna was composed of 47 taxa, including 26 taxa found in both pond contexts. The density of macroinvertebrates was higher in forest ponds. CCA analysis showed that conductivity and concentration of nitrates were most strongly associated with the distribution of gastropods. Alien snail species more often inhabited the roadside ponds.     

市政道路施工中的软基加固技术

简要介绍了软基的含义,分析了软土地基的危害和软土地基沉陷的影响因素,并对粉煤灰碎石桩、超压固结、强夯法、水泥土挤密桩处理法等几种常用的软土地基处理方法作了论述,以更好地解决道路工程中遇到的软基问题。     

基于差分主成分分析的特高压输变电工程线路施工道路水土保持监测研究

特高压输变电工程具有线路路径长、扰动区域分散等特点。其线路施工道路区是水土流失防治分区之一,监督管理相对困难。为了快速准确监测特高压输变电工程线路施工道路扰动,精细管控水土流失问题,开展智能化的水土保持监测研究十分必要。本文以锡盟-胜利1000kV特高压交流输变电工程为研究对象,利用差分主成分分析法快速准确识别出施工道路,从而监测其扰动。经现场验证,差分主成分分析法提取效果与目视遥感解译的效果基本一致。该方法可以为特高压输变电工程线路施工道路水土保持监测工作提供技术支撑。     

浅谈油路大修工程的施工工艺

在油路大修工程中，由于传统的灰土基层、沥青表面已不适应交通量猛增的要求，而被双基层、双面层结构所取代。介绍了目前油路大修中所采取的主要结构形式－－水稳砂砾基层，热拌沥青碎石3cm 2cm结构的施工工艺。从工前准备，水泥稳定砂砾基层的机械化施工至沥青碎石面层施工均作了详细说明。     

Sources and properties of non-exhaust particulate matter from road traffic: a review

While emissions control regulation has led to a substantial reduction in exhaust emissions from road traffic, currently non-exhaust emissions from road vehicles are unabated. These include particles from brake wear, tyre wear, road surface abrasion and resuspension in the wake of passing traffic. Quantification of the magnitude of such emissions is problematic both in the laboratory and the field and the latter depends heavily upon a knowledge of the physical and chemical properties of non-exhaust particles. This review looks at each source in turn, reviewing the available information on the source materials and particles derived from them in laboratory studies. In a final section, some of the key publications dealing with measurements in road tunnels and the roadside environment are reviewed. It is concluded that with the exception of brake dust particles which may be identified from their copper (Cu) and antimony (Sb) content, unequivocal identification of particles from other sources is likely to prove extremely difficult, either because of the lack of suitable tracer elements or compounds, or because of the interactions between sources prior to the emission process. Even in the case of brake dust, problems will arise in distinguishing directly emitted particles from those arising from resuspension of deposited brake dust from the road surface, or that derived from entrainment of polluted roadside soils, either directly or as a component of road surface dust.