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41.
Heggie  Ian G. 《Transportation》1999,26(1):87-111
Nearly all countries are seriously short of revenues for investment and maintenance of roads. Improving utilization of the existing road budget has helped to narrow, but not eliminate, this financing gap. Requests for additional resources from the government's budget have fallen on deaf ears, because the road sector has grown too large to be fully-financed through general tax revenues. Government tax systems were not designed to finance major economic sectors like roads. Faced with an acute shortage of funds, many road agencies have introduced tolls on high-volume roads and have invited the private sector to build and operate such roads under concession agreements. Although this has narrowed the financing gap, tolling is only economic on a small part of the road network. Tolls have thus had a relatively small impact on the financing gap. Against this background, and mindful of the fact that roads are now 'big business' on the scale of the Fortune Global 500, a growing number of countries have started to 'bring roads into the market place, put them on a fee-for-service basis and manage them like a business.' The fee-for-service concept, though superficially like the user-pay principle and the associated road funds which became popular during the 1950s, differs from user-pay in a number of important respects. The key differences are that: (i) only road user charges go into the road fund (i.e., there are no earmarked taxes); (ii) the fund is managed by a representative board with half or more members representing road users and the business community; (iii) members are nominated by the constituencies they represent and there is an independent chairperson; (iv) financing arrangements are designed to ensure that money is not diverted from other sectors; (v) funds are managed pro-actively by a small secretariat; (vi) there are published financial regulations governing the way funds are managed; (vii) charges are adjusted regularly to meet agreed expenditure targets; and (viii) there are regular technical and financial audits. Other important characteristics are that most commercially managed road funds are managed through a separate road fund administration, funds are channeled to all roads (sometimes even to unclassified roads) and they are introduced as part of a wider agenda to commercialize road management. Some of these road funds have been set up as road public utilities under a board with powers to set their own tariffs.  相似文献   
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澳大利亚昆士兰铁路(QR)于 2003 年 6 月 15 日采用世界上第一列窄轨(1 067 mm)内燃摆式列车,以改善北部沿海线路的运营等级。昆士兰铁路的凯恩斯摆式列车(CTT)是由负责设计、采购、制造、试验、试运行和项目管理的QR EDI/Walkers铁路联盟在昆士兰州马里伯勒的 Walkers工厂  相似文献   
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Park and ride facilities on light rail transit systems   总被引:2,自引:0,他引:2  
There is now considerable interest in exploring the idea of strategic park and ride as a means of promoting the use of rail transit and encouraging a transfer of commuters from car to public transport. This is especially evident in North America, where extensive park and ride facilities have been installed on a number of light and heavy urban rail systems. There is a general consensus about the most suitable types of location for facilities, but less agreement on the development of a reliable method of forecasting demand and also on the required size of sites. Experience in practice indicates that although park and ride is attractive to commuters, schemes do not generally result in lasting reductions in highway congestion, due to rising car ownership and use and the phenomenon of generated traffic.Abbreviations Centro West Midlands Passenger Transport Executive - K&R Kiss and ride - LRT Light Rail Transit - PT Public Transport - RT Rapid Transit - TRRL Transport & Road Research Laboratory, UK  相似文献   
44.
Because the reproductive fitness of a copepod is influenced by its ability to discriminate between conspecific and heterospecific mates, it is important to understand the mechanisms involved in these complex mate-recognition systems. Several lines of evidence suggest that chemical communication plays a role in mate location, recognition and reproduction in copepods. However, the relative importance of chemosensory cues, as well as other factors, including hydromechanical and morphological cues, remains unclear. Some studies show that mating ‘mistakes' occasionally occur in nature, which for species that mate only once, would have considerable effects on fitness. By reducing the likelihood of heterospecific matings, species-specific mate location and recognition chemicals have high adaptive value. The relative importance and molecular characteristics of these chemicals, whether diffusible or contact signals, may explain differences in premating and copulatory behavior observed among different copepod taxa. Current research suggests that both forms of chemical communication significantly influence the reproductive success of copepods. In this review, we summarize examples from the literature that may serve as a means to critically analyze postulated ideas and offer new questions for future study.  相似文献   
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在过去的一个世纪里,城市交通控制始终在演变,以适应日益复杂的政策目标和不断增长的交通需求。一个高效的交通控制系统可以带来很多收益,例如缓解拥堵、提高经济效益以及改善道路安全和空气质量。车辆检测和通信技术方面取得的显著进步为交通控制系统的调控能力带来了一系列阶段性变化:从早期(固定配时)信号控制发展到现代化的集成系统。多种类型的交通控制系统在全球不同地区建设完成,每种系统都有各自的优势和不足。首先通过对比分析目前占据领先地位的商用系统(以及一些较少为人所知的系统),凸显交通控制系统的关键特征和差异,然后评估目前的交通控制系统是否能实现现代交通政策的职能和需求。最后,探讨了当前及未来的交通政策,以及未来10年交通控制发展的技术性蓝图,指出交通控制有望通过技术进步从有限数据时代迈入大数据时代。  相似文献   
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