产能扩张带来质量隐患

从2009年中国取代美国成为世界上最大的汽车市场以来,汽车制造商已然进入了一场激烈的扩张竞赛。在过去两年里,数万亿元人民币涌入汽车制造行业。汽车制造商开始疯狂地扩大产能。按照这种扩张速度,中国的汽车年产能到201 3年将增至31 00万辆,达到2009年产能的两倍。而在中国开展业务的国际汽车制造商则显得保守一些。过去四年里,在占据全国乘用车一半产量的情况下,     

Nature and/or nurture? Analyzing the determinants of transit ridership across US urbanized areas

Public subsidy of transit services has increased dramatically in recent years, with little effect on overall ridership. Quite obviously, a clear understanding of the factors influencing transit ridership is central to decisions on investments in and the pricing and deployment of transit services. Yet the literature about the causes of transit use is quite spotty; most previous aggregate analyses of transit ridership have examined just one or a few systems, have not included many of the external, control variables thought to influence transit use, and have not addressed the simultaneous relationship between transit service supply and consumption. This study addresses each of these shortcomings by (1) conducting a cross-sectional analysis of transit use in 265 US urbanized areas, (2) testing dozens of variables measuring regional geography, metropolitan economy, population characteristics, auto/highway system characteristics, and transit system characteristics, and (3) constructing two-stage simultaneous equation regression models to account for simultaneity between transit service supply and consumption. We find that most of the variation in transit ridership among urbanized areas – in both absolute and relative terms – can be explained by factors outside of the control of public transit systems: (1) regional geography (specifically, area of urbanization, population, population density, and regional location in the US), (2) metropolitan economy (specifically, personal/household income), (3) population characteristics (specifically, the percent college students, recent immigrants, and Democratic voters in the population), and (4) auto/highway system characteristics (specifically, the percent carless households and non-transit/non-SOV trips, including commuting via carpools, walking, biking, etc.). While these external factors clearly go a long way toward determining the overall level of transit use in an urbanized area, we find that transit policies do make a significant difference. The observed range in both fares and service frequency in our sample could account for at least a doubling (or halving) of transit use in a given urbanized area. Controlling for the fact that public transit use is strongly correlated with urbanized area size, about 26% of the observed variance in per capita transit patronage across US urbanized areas is explained in the models presented here by service frequency and fare levels. The observed influence of these two factors is consistent with both the literature and intuition: frequent service draws passengers, and high fares drive them away.     

Increase in particle number emissions from motor vehicles due to interruption of steady traffic flow

We assess the increase in particle number emissions from motor vehicles driving at steady speed when forced to stop and accelerate from rest. Considering the example of a signalized pedestrian crossing on a two-way single-lane urban road, we use a complex line source method to calculate the total emissions produced by a specific number and mix of light petrol cars and diesel passenger buses and show that the total emissions during a red light is significantly higher than during the time when the light remains green. Replacing two cars with one bus increased the emissions by over an order of magnitude.     

Accessible pre-design calculation tool to support the definition of EV components

The new freedoms in design that electric powertrains offer lead to a wide variety of configurations to consider when developing an electric vehicle (EV) from scratch. Furthermore, the strong relation of the battery size with vehicle weight, range and performances leads to a set of interrelated dependencies that can result in many design loops to fulfil the vehicle targets, market constraints and regulations simultaneously. The paper presents a pre-design tool to assist the electric vehicle development process by representing the different constraints and the possible feasible solutions in a single plot with the need of a small amount of inputs accesible to assess at pre-design phase. As a result, the tool depicts a set of feasible vehicle configurations that could fulfil the targets easing the interaction and loops among different expertise areas. To better assist selection, it also provides a sensitivity analysis of the performances to selected inputs and the user can introduce a cost function depending on vehicle weight and battery size. The tool is based on the vehicle longitudinal dynamics equations and equations that model the market and regulations constraints. It is aimed at providing an overview of the main specifications for component selection avoiding detailed vehicle modelling in the early pre-design phase at which the vehicle characteristics and even powertrain architecture are unknown. Finally, the tool results quality is evaluated by further developing one of its solutions for passenger car in four different vehicle configurations with the simulation software vemSim and AVL Cruise. The results of the simulations are compared to the solution of the pre-design tool to evaluate the level of fidelity and the deviations in the final result that can appear depending on the final architecture, components characteristics and control strategy.     

Traffic models for goods,service and business movements to manufacturing establishments

This paper is concerned with a problem area of increasing interest, namely the traffic characteristics of specific generators located on non‐residential land use. It concentrates on the problem of modelling traffic generation for goods, service and business movements at the manufacturing establishment. Firstly the contributions of earlier researchers are reviewed in the context of factors which have been considered important. Then a further study conducted by the author in Sheffield and in Manchester, England, is described. This study considers more rigorously than hitherto the questions of similarities in trip rates over different manufacturing activities and geographical areas, and of the choice of explanatory variables. Comparison of regressions is used to formalize indications of similarities in trip rates, and analysis of variance for choosing the most satisfactory explanatory variables. The study provides evidence of similarity in trip rates over seven different manufacturing activities and two geographical areas. It also shows distinctions between different non‐work traffic types in the extent of similarities in trip rates over different manufacturing activities and in explanatory variables for traffic generation relationships. Regarding the latter it is concluded that it is not possible to model accurately such traffic movements on the basis of explanatory variables which are normally available. Instead trip rates should be expressed in simple mathematical terms and should be based on large data populations. The study also makes contributions on peak flow factors for the actual design of facilities of manufacturing establishments. These findings and others are discussed in the context of the work of earlier researchers. Finally conclusions are drawn and guidance offered for future work into this problem.     

The economics of bus deregulation in Britain

This paper reviews some of the arguments which have been put forward on the economics of bus deregulation, particularly the paper by Gwilliam and others. It argues that the experience of road haulage licensing is relevant. The evidence there suggests that liberalization has not had the adverse effects that many predicted and that in most respects one could expect bus deregulation to have no less favourable consequences. The main difference between buses and road haulage is over how far bus drivers might revert to the old practices of the 1920s of chasing, tailing, etc. which were said at the time to be a major cause of consumer dissatisfaction. The paper reviews the economics of some of these practices and suggests which might be discounted and which need further attention.     

Public involvement in offshore oil development: Lessons from New England

Abstract

Public perceptions of the risks and benefits of offshore oil development off the New England coast are examined. The influence of these perceptions on state policies toward federal actions is analyzed. A distinct trend of issue identification, critical analysis, consensus building, and state or regional action is observed. Throughout this interactive process between the region and the federal government, even though divergent state positions have evolved, there is a growing regional acceptance of coastal zone management concepts.     

Shoreline Management Plans and Coastal Cells in Scotland

Coastal sediment cells have been identified for the Scottish coast and, following the example of England and Wales, a trend is emerging towards the production of shoreline management plans (SMPs) for parts the Scottish coast. However, much of the Scottish coast does not have the degree of intracoastal sediment exchange that gives coastal sediment cells their integrity, and so a cell-based strategy for coastal management may not be a suitable response. This article examines the nature of the sediment cells in Scotland, questions whether the adoption of SMPs for all sections of the coastline is an appropriate management response, and suggests alternatives that may better link to integrated coastal zone management.