Objective: The objective of this article is to provide empirical evidence for safe speed limits that will meet the objectives of the Safe System by examining the relationship between speed limit and injury severity for different crash types, using police-reported crash data.
Method: Police-reported crashes from 2 Australian jurisdictions were used to calculate a fatal crash rate by speed limit and crash type. Example safe speed limits were defined using threshold risk levels.
Results: A positive exponential relationship between speed limit and fatality rate was found. For an example fatality rate threshold of 1 in 100 crashes it was found that safe speed limits are 40 km/h for pedestrian crashes; 50 km/h for head-on crashes; 60 km/h for hit fixed object crashes; 80 km/h for right angle, right turn, and left road/rollover crashes; and 110 km/h or more for rear-end crashes.
Conclusions: The positive exponential relationship between speed limit and fatal crash rate is consistent with prior research into speed and crash risk. The results indicate that speed zones of 100 km/h or more only meet the objectives of the Safe System, with regard to fatal crashes, where all crash types except rear-end crashes are exceedingly rare, such as on a high standard restricted access highway with a safe roadside design. 相似文献
Codigestion of five wastes and municipal wastewater sludge was evaluated using full-scale testing. Synergistic, antagonistic, and neutral outcomes were observed depending on codigestate identity and concentration, highlighting the value of careful blending. Yeast waste resulted in notable synergism, increasing biogas production by over 50%, whereas aircraft deicing waste resulted in antagonism at high loadings and neutral outcomes at lower loadings. Restaurant waste codigestion resulted in neutral outcomes. The synergisim with yeast codigestates may have resulted from trace nutrients (i.e., iron, nickel, and cobalt) in the wastes that increased microbiological activity. Antagonist outcomes with deicing waste may have been the result of organic overload or inhibitory deicer constituents. Codigestion of wastes at the feed rates investigated was estimated to produce 0.50 ML/d of methane having an energy equivalent of 17 500 MJ/d. This was estimated to reduce net carbon dioxide emissions by 560 tonnes/y. 相似文献
The potential health risks due to inorganic substances, mainly metals, was evaluated for the two resident marine mammals in Hong Kong, the Indo-Pacific Humpback Dolphin (Sousa chinensis) and the Finless Porpoise (Neophocaena phocaenoides). The stomachs from the carcasses of twelve stranded dolphins and fifteen stranded porpoises were collected and the contents examined. Concentrations of thirteen trace elements (Ag, As, Cd, Co, Cr, Cs, Cu, Hg, Mn, Ni, Se, V and Zn) were determined by inductively coupled plasma mass spectrometer (ICP-MS). An assessment of risks of adverse effects was undertaken using two toxicity guideline values, namely the Reference Dose (RfD), commonly used in human health risk assessment, and the Toxicity Reference Value (TRV), based on terrestrial mammal data. The levels of trace metals in stomach contents of dolphins and porpoises were found to be similar. Risk quotients (RQ) calculated for the trace elements showed that risks to the dolphins and porpoises were generally low and within safe limits using the values based on the TRV, which are less conservative than those based on the RfD values. Using the RfD-based values the risks associated with arsenic, cadmium, chromium, copper, nickel and mercury were comparatively higher. The highest RQ was associated with arsenic, however, most of the arsenic in marine organisms should be in the non-toxic organic form, and thus the calculated risk is likely to be overestimated. 相似文献
A well sampling study was conducted to evaluate anempirical approach to classifying areasof land in California as vulnerable to ground watercontamination by pesticides (Troiano et al., 1994). Wells were sampled from sections of land that had noprevious detections of pesticideresidues. The sections had been classified into vulnerablesoil clusters or into a not-classified groupusing a procedure based on Principal Components Analysis(PCA). Grape, citrus, and olive growingareas of Fresno and Tulare Counties were targeted, areas wherepre-emergence herbicide residues hadbeen detected in well water. Overall, herbicide residues weredetected in 75 of 176 sampled wells, ahigh frequency of detection in relation to results fromprevious targeted well sampling studies. Sinceresidues were also detected in the not-classified group, theclassification procedure was modified usingan approach based on Canonical Variates Analysis (CVA). Moresections were classified intovulnerable soil clusters with the CVA approach than with thePCA method. Data from two otherexplanatory variables, depth to ground water and amount ofpesticide used per section, were includedto illustrate how additional information can be incorporatedinto this approach of identifying vulnerable areas. 相似文献
The de-O-sulphation of α-linked glucosamine-6-sulphate residues in heparan sulphate requires a specific sulphatase, glucosamine-6-sulphatase, which has been shown to be deficient in tissues of Sanfilippo D, or mucopolysaccharidosis type IIID (MPS IIID), patients. MPS IIID fibroblasts cultured in Basal Eagle's medium supplemented with either fetal calf serum or heat-inactivated fetal calf serum, MDCB or Ultraserg media had residual glucosarnine-6-sulphatase activities towards a heparin-derived trisaccharide substrate, O-(α-N-acetylglucosamine-6-sulphate)-(1→4)-L -O-(α-iduronic acid-2-sulphate)-(1→4)-D -O-2,5-anhydro [1-3H]mannitol-6-sulphate, GlcNAc6S-IdoA2S-anM6S, which were less than 1 per cent of the normal range for fibroblasts cultured in Basal Eagle's medium supplemented with fetal calf serum. However, the glucosamine-6-sulphatase activities of MPS IIID fibroblasts grown in Chang's medium were similar to the activities in normal control fibroblasts which were cultured in Basal Eagle's medium. These results indicate that caution is required for prenatal diagnosis of MPS IIID patients using chorionic villi or amniotic cells cultured in Chang's medium. 相似文献
A wide range of fiscal measures for natural resource based projects are analyzed in this paper. Maximizing government revenue involves taxing heavily any rents generated in the project while retaining the incentive to invest. Recovery efficiency must also be preserved. Based upon the principles of resource economics and project appraisai a series of tests are derived and applied to alternative tax schemes in order to assess their efficiency in maximizing the present value of government revenues. The tests indicate that of the ten schemes examined, the most likely to achieve revenue maximization is a progressive resource rent tax incorporating a safeguard tapering provision and superimposed upon normal corporate income tax. Many commonly applied taxes are demonstrated to have serious distortionary effects on the investment decision and to fail to capture a large proportion of rents generated. Cet article analyse une gamme variée de mesures fiscales applicables aux projets concernant les ressources naturelles. L'optimisation des recettes de l'Etat implique une lourde imposition des revenus provenant du projet tout en continuant à encourager les investissements. L'efficacité de la relance doit aussi être maintenue. Sur la base des principes de l'économie des ressources et de l'évaluation des projets, une série de tests a été conçue et appliquée à des systèmes fiscaux alternatifs afin de permettre l'évaluation de leur efficacité en ce qui concerne l'optimisation de la valeur actuelle des recettes de l'Etat. Les tests indiquent que sur les dix systèmes examinés, le plus susceptible d'optimiser les recettes semble être un impôt progressif sur les revenus provenant des ressources qui incorpore une clause de garantie dégressive et qui vient s'ajouter à l'impôt sur le revenu des sociétés habituel. L'article démontre que de nombreux impôts habituellement appliqués présentent de sérieux effets de distortion ayant un impact sur la décision d'investir et qu'une grande proportion des revenus de ces projets échappe à l'imposition. En este artículo se analiza una gama amplia de medidas fiscales sobre proyectos relacionados con recursos naturales. Maximizar los ingresos fiscales requiere imponer fuertes impuestos sobre las rentas generadas por el proyecto manteniendo al mismo tiempo el incentivo para la inversión. Debe mantenerse también la eficiencia en la recuperación de los recursos en cuestión. Basado en principios de la economía de recursos y de evaluación de proyectos se derivan una serie de pruebas sobre esquemas alternativos de aplicación de impuestos con el objeto de evaluar la eficiencia de dichos esquemas en la maximización del valor presente del ingreso del gobierno por concepto de impuestos. Las pruebas indican que de los diez esquemas examinados, el que con mayor probabilidad va a maximizar el ingreso del gobierno es el impuesto progresivo sobre la renta del recurso con un provisión de salvaguarda la reducción de dicho impuesto, más un impuesto simultáneo sobre el ingreso de la empresa. Muchos de los esquemas de imposición comúnmente aplicados tienen serios efectos distortionadores sobre las decisiones de inversión y consecuentamente impiden la colección de una gran parte de las rentas generadas. 相似文献
ABSTRACT: Computer programs that model the fate and transport of organic contaminants through porous media typically use Fick's first law to calculate vapor phase diffusion. Fick's first law, however, is limited to the case of a single, dilute species diffusing into a stagnant, high concentration, bulk vapor phase. When dealing with more than one diffusing species and at higher concentrations, the multicomponent coupling effects on vapor phase diffusion and advection of the various constituents become significant. VLEACH, a one‐dimensional finite difference model developed for the U.S. Environmental Protection Agency (USEPA), is typical of the models using Fick's first law to model vapor‐phase diffusion. The VLEACH model was modified to accommodate up to 10 components and to calculate the binary diffusion coefficients for each of the components based on molecular weight, molecular volume, temperature and pressure, and to address the coupling effects on multiple component vapor phase diffusion and its impact on ground water. The resulting model was renamed MC‐CHEMSOIL. At low vapor phase concentrations, MC‐CHEMSOIL predicts identical ground water impacts (dissolved phase loading) to those from VLEACH 2.2a. At higher vapor phase concentrations, however, the relative difference between the models exceeded 20 percent. 相似文献
In the wake of the flood that affected Brisbane, Australia, in January 2011, public attention turned to the causes of the event and lessons for minimizing the impacts of future floods. The news media was an important vehicle for understanding and internalizing the 2011 Brisbane flood. Examining how the flood was framed in the media is, therefore, useful to understand broad public perception of floods. We undertook a systematic newspaper analysis during a one-year period to explore media framings of the flood, focused on learning as an aspect of resilience in relation to two themes: (1) perceived links between the flood and climate change and (2) perceived roles of government in managing the flood. We show that media coverage of the flood reinforces aspects of resilience by acknowledging community spirit, self-reliance and the importance of sharing experiences for learning; articulating the risk of extreme events in a changing climate; and highlighting regional management trade-offs. Much of the discourse is likely to inhibit resilience, however, by casting the flood in terms of blame and political opportunity and paying inadequate attention to longer-term aspects of regional resilience. The limited learning observed to date may highlight a need for other mechanisms and actors to lead learning processes. As policy related to the 2011 Brisbane flood, and extreme events more generally, is influenced by the public discourse, it is important to understand the nuances of communication around these events and the media’s role in reinforcing or changing perceptions. 相似文献
Freshwater ecosystems are important for global biodiversity and provide essential ecosystem services. There is consensus in the scientific literature that freshwater ecosystems are vulnerable to the impacts of environmental change, which may trigger irreversible regime shifts upon which biodiversity and ecosystem services may be lost. There are profound uncertainties regarding the management and assessment of the vulnerability of freshwater ecosystems to environmental change. Quantitative approaches are needed to reduce this uncertainty. We describe available statistical and modeling approaches along with case studies that demonstrate how resilience theory can be applied to aid decision-making in natural resources management. We highlight especially how long-term monitoring efforts combined with ecological theory can provide a novel nexus between ecological impact assessment and management, and the quantification of systemic vulnerability and thus the resilience of ecosystems to environmental change. 相似文献