The modified golden rule of a multi-sector economy

We consider an n-good model of optimal accumulation determined by a technology, a utility function, and a discount factor. A technology is δ-productive if it contains an input-output pair such that the discounted output vector strictly dominates the input vector. We show that a δ-productive technology has a non-trivial modified golden rule. We also report a counter- example of David Starrett showing that the modified golden rule need not have turnpike properties, and that there may exist non-trivial periodic optimal consumption plans even when there is no non-trivial modified golden rule.     

Minibuses in urban transportation

Bus-route simulations suggest that minibuses could not survive in North America or Europe if driver wages equal those currently paid mass-transit bus drivers. If minibuses pay taxi-driver wages and standard buses pay current wages, however, minibuses would yield slightly and appreciably lower urban travel costs than standard buses given respectively marginal-cost and current prices for road services. Scale economies justify markedly smaller subsidies for minibuses than for standard buses. Underpriced road services justify substantial subsidies and preferential access to road capacity for both minibuses and standard buses.     

城市空间互补与城市交通问题

聚集效应主要决定于城市区域空间之间的互补性,而与土地价格不存在互为因果的关系.城市区域空间互补性越强,聚集经济越大,资源空间布局越有效率,城市通勤距离也越短.由此才可以形成有效率的城市多中心空间形态.大都市交通问题的根源在于城市资源空间布局的非互补性.     

The impact of alternative transportation systems on urban structure

This paper extends a recent von Thünen-type model of urban structure by Mills to include two competing forms of transportation, and then compares simulated representative American and European cities with respect to size, density, and land rents. Assuming consumers minimize costs in choosing between competing travel modes, the 19-equation model demonstrates that land rent differentials are diminished by adding an alternative travel mode, and that transport capacity is far more important than fare structures in determining transit patterns and land use. American urban structure appears to resemble European urban patterns as transportation modes proliferate.     

The impact of transportation cost uncertainty on urban structure

Under an uncertain transportation cost, residential choice is made before the actual state of the world reveals itself. Formally, this resembles the theory of saving under uncertainty. Exploring this resemblance, we investigate the effect on urban structure of introducing uncertainty in transportation cost. Our main conclusion is that risk does not necessarily have the same effect on the city that an increase in transportation cost does in the deterministic case. If the utility function obeys the ‘principle of decreasing risk aversion to concentration’, introducing risk causes the urban area to contract (as in the case of an increasing transportation cost), but the equilibrium utility level may either increase or decrease. If, on the other hand, utility does not satisfy the above principle, introducing risk causes the utility level to decline (as if the case of an increasing transportation cost), but the urban area may either expand or contract.     

城市交通与城市空间演化相互作用机制研究

认为城市交通与城市空间演化之间存在着持续的相互作用关系:一方面,城市空间演化不断对城市交通提出更高的要求,并为城市交通的发展提供相应的条件;另一方面,交通可达性的提高和交通方式的变革又会对城市空间的进一步演化产生引导作用,它们之间通过可达性这一关键因素的不断调整和变化实现相互促进和共同发展.     

基于分形方法的城市路网交通形态分析

城市路网交通形态的合理与否是关系到城市交通顺畅与否的基础性要素.运用分形理论及其方法,针对路网覆盖性与连通性,分别建立相应的分形模型,进而通过探讨模型分形意义下的维数,达到分析城市路网交通形态的目的.最后,通过对某城市局部路网的实例分析,验证了将分形方法引入城市路网交通形态分析的可行性.     

城市中心区交通模式研究

伴随着城市化的迅猛发展及新一轮城市总体规划的调整 ,我国城市不仅面临着城市规模的不断扩大 ,而且面临着城市内部的功能调整。城市用地结构的变化主要集中于两个方面 :城市郊区化及城市中心区的整治。城市郊区化推动的人口和产业的外迁 ,为城市中心区产业结构的重组与功能的优化创造了的条件。不少城市已经将建设中央商务区提上议事日程。城市中心区一般位于城市的几何中心 ,是城市发展历史最长、土地使用强度最高、公共活动强度最大的地区 ,城市中心区的发展面临环境、人口的一系列压力 ,其中如何建立高效、便捷的城市交通系统是目前各大…     

住房、交通与城市空间规划

首先归纳了城市空间结构理论框架下居住模式和交通体系空间互动关系的基本理论,之后对国际学术界相关的定量研究成果进行了综述,着重讨论了住房与交通相互作用所形成的社会效应,包括对居民住房支付能力、中低收入者福利和环境的影响,最后提出了住房和交通相协调的城市空间规划的三个目标,并就我国目前的实际情况提出了若干政策建议.     

The effects of transportation system improvements on urban performances with heterogeneous residents

Through developing a spatial equilibrium model for a linear monocentric city with a bi-modal traffic corridor (i.e., highway and public transit), this paper examines the effects of transportation improvements (including the decreases of the fixed travel cost, the travel time and monetary cost per unit distance) on urban spatial structure and the utilities of the two resident classes, namely car-available-residents (CARs) and car-unavailable-residents (CURs). As a result, it is demonstrated that the city size increases with the improvements of vehicle-highway system and the degree of CARs’ travel mode choice rationality, but the improvement of public transit may produce a shrinkage rather than an expansion in city size. From the aspect of utility, both CARs and CURs benefit from the improvement of vehicle-highway system; however, the improvement of public transit might have an adverse effect on the utility of CARs. These findings would provide valuable reference for the future transportation and urban planning.     

城市交通出行影响因素的计量检验

在国内外相关研究的基础上,通过国内40个交通出行样本数据的计量分析,建立了平均出行距离和出行时耗的多元回归方程,发现城市规模是影响单中心城市平均出行距离和出行时耗的主要因素,公交车分担率的提高相应增加了平均出行时耗,而高密度的城市开发有利于出行距离和出行时耗的降低.     

公共交通建设与城市可持续发展

分析了现有城市交通体系存在的问题和城市交通体系发展的可持续性,认为应在大中城市建设以轨道交通系统为主干的区域性综合公共交通体系,并提出城市交通体系可持续发展的建议.     

改善中国城市交通与环境问题

本文系中国环境与国际发展合作委员会环境与交通专家工作组在对国内外十多个城市交通与环境状况调查的基础上 ,经过一年多认真分析研究提出的《改善中国城市交通与环境问题的建议书》。建议书对我国当前城市交通问题的分析较准确 ,所提出的观点鲜明、政策与措施建议针对性较强。现特刊出供读者学习参考。     

Time-varying road network design for urban hazmat transportation

Hazmat transportation in cities faces significant risks that may cause catastrophic losses to humans. From the perspective of the regulator, the main responsibility is to mitigate hazmat transport risk by determining the availability of road networks to hazmat carriers. Based on the time-variant population distribution, the hazmat transport risk was assessed via the total population exposure associated with the resident and variable populations at different times. We propose a risk-minimizing urban hazmat road network design model for multiple types of hazmats, considering time-varying traffic. The model was applied to a realistic case study of hazmat transportation in a densely populated urban area with complex traffic in Shanghai, China.     

城市公共交通工具的色彩及其规划

城市公共交通工具的色彩是城市色彩的重要组成部分。只有根据城市环境特点、文化气质及色彩规律规划科学的色彩方案,才能将流动风景亮丽明快的色彩传递给人们,从而提高公共交通工具自身的识别性。城市公共交通工具与其他元素共筑城市色彩,能够展示出城市的精神风貌、体现城市品位。     

城市投资环境综合评价方法研究

为了提高城市投资效率与效果,通过定性设置城市投资环境的总体评价指标体系,对影响投资环境的因素利用综合评价的方法做出定量的评价,得出各个因素之间的权重及排序,可以找出城市投资环境存在的优势与不足,以利于改善投资环境.     

城市交通与城市空间结构演变

通过回顾城市交通和城市空间结构的发展演变过程,研究通过城市交通引导城市空间结构健康"生长"的有效途径,提出通过公共交通引导城市发展的TOD模式,以及适合中国特色的和谐城市形态和城市交通.     

国外城市公共交通财政补贴政策研究

城市公共交通是城市交通系统的重要组成部分 ,为促进城市公共交通事业的发展 ,保障公交企业的正常运营 ,世界各发达国家和地区无不实行了公交财政补贴政策。本文在若干发达国家公交财政补贴政策分析的基础上 ,结合我国城市的特点 ,提出了我国城市公交财政补贴的改进建议。     

城市制度:城市发展的核心构架

讨论了城市制度的本质、结构、功能及我国城市的发展模式 ,提出城市制度不完善是我国城市发展滞后的重要原因 ;建构与转换城市制度是城市发展进入自觉阶段的根本标志。我国城市要实现跨越式发展 ,应以制度创新为先导