Measuring hierarchical differentiation: connectivity and dominance in the European urban network

Abstract

This paper presents an examination of the empirical merits of a set of spatial interaction indices for measuring hierarchical differentiation (i.e. dominance and connectivity) in a spatial network. To allow for the comparison of the degree of hierarchical differentiation in networks with different numbers of nodes/links, we propose to normalize the ratio between the real measures and the corresponding values for a rank size distribution in order to obtain readily interpretable measures of hierarchical differentiation. When applied to data on air passenger flows within Europe, the normalized indices, interpreted together, appear to give a good idea of the tendency toward hierarchical differentiation. The potential usefulness of this analytical framework is discussed in the context of studies on (transnational) inter-city relations and empirical assessments of changes in the spatial configuration of airline networks.     

Automated vehicles: exploring possible consequences of government (non)intervention for congestion and accessibility

ABSTRACT

Academic research on automated vehicles (AVs) has to date been dominated by the fields of engineering and computer science. Questions of how this potentially transformative technology should be governed remain under-researched and tend to concentrate on governing the technology’s early development. We respond in this paper by exploring the possible longer-term effect of government (lack of) intervention.

The paper tests the hypothesis that a “laissez-faire” governance approach is likely to produce less desirable outcomes in a scenario of mass uptake of AVs than would a well-planned set of government interventions. This is done using two prominent themes in transport policy – traffic flow and accessibility – in a scenario of high market penetration of Level-5 automated vehicles in capitalist market economies. The evidence used is drawn from a literature review and from the findings of a set of workshops with stakeholders.

We suggest that a laissez-faire approach will lead to an increase in traffic volume as a result of a growing population of “drivers” and a probable increase in kilometres driven per passenger. At the same time, the hoped-for increases in network efficiency commonly claimed are not guaranteed to come about without appropriate government intervention. The likely consequence is an increase in congestion. And, with respect to accessibility, it is likely that the benefits of AVs will be enjoyed by wealthier individuals and that the wider impacts of AV use (including sprawl) may lead to a deterioration in accessibility for those who depend on walking, cycling or collective transport.

We consider the range of possible government intervention in five categories: Planning/land-use; Regulation/policy; Infrastructure/technology; Service provision; and Economic instruments. For each category, we set out a series of interventions that might be used by governments (at city, region or state level) to manage congestion or protect accessibility in the AV scenario described. Many of these (e.g. road pricing) are already part of the policy mix but some (e.g. ban empty running of AVs) would be new. We find that all interventions applicable to the management of traffic flow would also be expected to contribute to the management of accessibility; we define a small number of additional interventions aimed at protecting the accessibility of priority groups.

Our general finding is that the adoption of a package of these interventions could be expected to lead to better performance against generic traffic-flow and accessibility objectives than would a laissez-faire approach, though questions of extent of application remain.

In our conclusions, we contrast laissez-faire with both anticipatory governance and “precautionary” governance and acknowledge the political difficulty associated with acting in the context of uncertainty. We point out that AVs do not represent the first emerging technology to offer both opportunities and risks and challenge governments at all levels to acknowledge the extent of their potential influence and, in particular, to examine methodically the options available to them and the potential consequences of pursuing them.     

Hinterland strategies of port authorities: A case study of the port of Barcelona

Port authorities generally focus on the development of the local port area and play a minor role in the development of port hinterlands, whereas shippers, forwarders, barge and rail operators have always been involved in the port-hinterland connection. The increasing importance of intermodal hinterland networks for the competitive position of ports has urged port authorities to become active in the hinterland. This new role has already been suggested by different academics. However, limited empirical evidence exists of port authorities taking stakes in inland terminals or developing transport services. Barcelona, as one of the leading port authorities in this respect, is used as a case study in this paper. The case study provides insight in the components and execution of the hinterland strategy of Barcelona. It shows that the strategy of the port authority of Barcelona and the consequent active involvement in the hinterland has had a significant impact on attracting container volumes from distant hinterlands and improving the accessibility of the port.     

BUICK轿跑

编辑老师们好：有几个问题想请教一下。非常感谢! 1．大众的发动机的缸体材料大多数都是铁质的。而其它很多厂家的都是铝制的,请问这两种材料对发动机的寿命、燃油效率、输出功率和扭矩、制作成本和后期维护等方面有什么不同。如果是铝的好。那么大众这样做的原因是降低成本吗？     

混合动力车辆的技术特征及其故障诊断与维修

当一辆混合动力车辆被送到你的修理厂请求维修时,你是选择让客户将这辆车送回到经销商那儿去修理,失去赢得一个新客户的机会;还是选择主动努力学习,掌握修理混合动力车辆新的检测维修技术呢?显然,为了服务于客户,也为了拓展自身维修厂的业务,我们应该选择后一种态度。     

Design of a Stroke Dependent Damper for the Front Axle Suspension of a Truck Using Multibody System Dynamics and Numerical Optimization

Summary A stroke dependent damper is designed for the front axle suspension of a truck. The damper supplies extra damping for inward deflections rising above 4 cm. In this way the damper should reduce extreme suspension deflections without deteriorating the comfort of the truck. But the question is which stroke dependent damping curve yields the best compromise between suspension deflection working space and comfort. Therefore an optimization problem is defined to minimize the maximum inward suspension deflection subject to constraints on the chassis acceleration for three typical road undulations. The optimization problem is solved using sequential linear programming (SLP) and multibody dynamics simulation software. Several optimization runs have been carried out for a small two degree of freedom vehicle model and a large full-scale model of the truck semi-trailer combination. The results show that the stroke dependent damping can reduce large deflections at incidental road disturbances, but that the optimum stroke dependent damping curve is related to the acceleration bound. By means of vehicle model simulation and numerical optimization we have been able to quantify this trade-off between suspension deflection working space and truck comfort.     

压力钢带式无级变速器技术降低油耗的潜能分析(二)

参考CVT装在一辆奔驰A190车辆上，在3个测试循环及两种恒速状态下，通过认可的方法对油耗进行测量。表2所示的是采用绝对安全系数Sfabs=1.3的目前策略与新的控制策略之间的减少量。     

Requirements from vehicle routing software: perspectives from literature,developers and the freight industry

Routing and scheduling software is part of the information and technology systems available to support the transport industry, and uses complex algorithms along with geographical representations of the road network to allow better planning of daily collection and delivery schedules. This paper reviews the evolution of routing and scheduling software, the algorithms used along with reported barriers to wider take-up and potential industry-driven improvements that could be made. A survey of transport companies in the U.K. was conducted in order to validate and prioritise the software capabilities that require the most development according to the new challenges that the industry is facing. Responses suggested that companies required improved route optimisation to tackle congestion based on time-dependent data and models, and greater accuracy in the representation of the road network. Not considering congestion leads to the underestimation of travel times and the production of inaccurate schedules. Literature shows that operational research techniques are available to solve problems that represent real-world conditions, but research into the relative merits of using time-dependent models needs to be undertaken. Data might be improved by cooperation between government and private sector.     

Travel plans for new developments: a global review

A travel plan is a mechanism for delivering a package of transport measures at a site to manage car use and encourage the use of more sustainable forms of transport. In recent years, travel plans have been required for new infill and greenfield developments through the land-use planning and approvals process, predominantly in the United Kingdom, the United States, continental Europe and Australia. This paper contributes to the literature by providing a global review of travel plans for new developments. The results show that while travel plans for new developments share a common set of elements with those for pre-existing sites, differences within each element are notable, particularly in the types of travel plan measures adopted, processes for managing the travel plan, and approaches to monitoring and review. Results of previous evaluations have varied considerably, although most have reported a reduction in car driver trips of 10–20 percentage points. Despite this, most evaluations lack rigour, with a paucity of robust evidence. Key success factors identified by the literature, such as the provision of an explicit policy supporting the role of travel plans, should be embedded within the travel planning process where possible to ensure best outcomes for new developments.