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ABSTRACT Using official national data for each country, this article calculates trends in walking and cycling fatalities per capita and per km in the USA, the UK, Germany, the Netherlands, and Denmark. From 1990 to 2018, pedestrian fatalities per capita fell by 23% in the USA vs. 66%–80% in the other countries; cyclist fatalities per capita fell by 22% in the USA vs. 55%–68% in the other countries. In 2018, pedestrian fatality rates per km in the USA were 5–10 times higher than in the other four countries; cyclist fatality rates per km in the USA were 4–7 times higher. The gap in walking and cycling fatality rates between the USA and the other countries increased over the entire 28-year period, but especially from 2010 to 2018. Over that 8-year period, per-capita fatality rates in the USA rose by 19% for pedestrians and 11% for cyclists; per-km fatality rates rose by 17% for pedestrians and 33% for cyclists. By comparison, fatality rates either fell or remained stable in the four European countries. We reviewed the relevant literature to identify factors that might help explain the much lower walking and cycling fatality rates in Europe compared to the USA. Possible explanatory factors include better walking and cycling infrastructure; lower urban speed limits; fewer vehicle km travelled; smaller and less powerful personal motor vehicles; and better traffic training, testing, and enforcement of traffic regulations. We recommend that the USA consider implementing an integrated package of mutually reinforcing safety measures such as those that have been successfully implemented in the Netherlands, Denmark, and Germany to reduce pedestrian and cyclist fatality rates. 相似文献
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针对牵出线长度比较短,无法停放一整列溜放车列的情况,需要将牵出线延伸至出发场咽喉区,对此本文提出一种场间联系方案,并对电路细节进行分析和设计. 相似文献
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Anouk de Brauwere Fjo De Ridder Marc Elskens Johan Schoukens Rik Pintelon Willy Baeyens 《Journal of Marine Systems》2005,55(3-4):205-221
The problem of estimating parameters and their uncertainty from experimental measurements in marine ecosystems is a common task and often necessitates solving nonlinear equations. If the measurements are subject to individually varying errors (i.e., heteroscedastic data), the parameters are often estimated using a Weighted Least Squares (WLS) method. For estimating the parameter uncertainties, a linearized expression for the covariance matrix exists. Yet, both methods assume that the errors on the independent variable, also called “input”, is negligible, which is often not true. For instance, in order to determine uptake and regeneration rates of silicic acid by phytoplankton, concentration and isotopic abundance measurements are performed at the beginning (input) and at the end (output) of an incubation experiment. Here, the so-called input and output are measurements of the same quantities, i.e., determined in exactly the same way, only differing by the time at which the measurements were performed. Clearly, there is no reason to assume that the input measurements are subject to less error than the output measurements. We propose a refinement of the two abovementioned estimation methods which enlarges their applicability to cases where input noise is not negligible. The refined methods are evaluated on the uptake and regeneration processes of silicic acid and compared to the original procedures using Monte-Carlo simulations. The results reveal a smaller bias for the refined WLS estimator compared with the original one. An additional advantage of using the refined WLS cost function is that its residual value can be interpreted as a sample from a χ2 distribution. This property is especially useful because it enables an internal quality control of the results. In addition, the parameter uncertainty estimation is significantly improved. By neglecting the effect of the input noise, a (potentially) important origin of the parameter variation is simply ignored. Therefore, without the refinement, the parameter uncertainties are systematically underestimated. Using the refined method, this systematic error disappears and on the whole, the parameter standard deviations are accurately estimated. 相似文献
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铅芯橡胶支座隔震铁路简支梁桥双向地震响应分析 总被引:6,自引:0,他引:6
采用铅芯橡胶支座,选取具有不同固有周期的4座铁路简支梁桥桥墩,建立空间有限元模型。以7组典型地震波作为激励,进行铅芯橡胶支座隔震铁路简支梁桥的双向地震响应分析。采用时程分析法计算考虑和不考虑铅芯橡胶支座恢复力耦合作用的隔震桥墩系统的地震响应。分析结果表明:双向地震动作用下考虑耦合作用的铅芯橡胶支座的位移—恢复力曲线与单向地震作用下不考虑双向恢复力的耦合作用时的位移—恢复力曲线在形状上存在较大差别,铅芯橡胶支座的滞回耗能也不相同;不同地震激励下铅芯橡胶支座恢复力的耦合作用对铅芯橡胶支座峰值位移的影响程度不同;随着桥墩一阶固有周期的增加,铅芯橡胶支座恢复力的耦合作用对一阶振型方向的支座峰值位移的影响程度逐渐增大;梁体的峰值地震响应的规范计算值大都高于实际值,故按照规范值进行铁路简支梁桥的隔震设计偏于安全。 相似文献
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为解决中厚板高强钢埋弧焊(Submerged Arc Welding, SAW)焊缝热影响区(Heat Affected Zone, HAZ)热循环参数准确测量难题,自主研制多通道热电偶测温软/硬件系统,测量并比较不同焊丝组合(单丝和冷热多丝复合)对应的焊缝HAZ热循环主要参数。试验结果表明:与单丝SAW工艺相比,冷热多丝复合SAW工艺可解决SAW较大热输入产生的焊缝HAZ脆化问题,提高焊缝组织性能和焊接质量;在中厚板高强钢焊接过程中,冷热多丝复合SAW工艺可为温度场数值模拟计算分析提供实测数据,为各种工艺参数的确定与优化、焊缝HAZ的组织性能改善提供必要的理论基础。 相似文献