An efficient algorithm for building min-path trees for all origins in a multi-class network

Urban transportation planning models consume untold hours of computer time building zillions of min-path trees. Their networks have tens of thousands of arcs, accommodate several trip classes, and solve the traffic equilibrium problem via many, many iterations of min-path calculations for thousands of origins and destinations. This paper presents a simple algorithm that couples restricted reduced-cost analysis with label-correcting, which can reduce this min-path tree building time substantially. For a given origin, the algorithm rapidly transforms a tree for one class to that for next class. Test results using synthetic data suggest that its application to real networks should experience speedups of at least a factor of 2.0 and perhaps beyond 5.0.     

Status and Priority Capacity Needs for Local Compliance and Community-Supported Enforcement of Marine Resource Rules and Regulations in the Coral Triangle Region

Combating illegal and destructive resource exploitation in the Coral Triangle is central to ensuring the long-term effective management of fisheries, marine protected areas, and climate change adaptation efforts. This article presents results of an investigation of the perceived level of local compliance and enforcement with marine resource rules and regulations and evaluates the effectiveness or potential for community-supported enforcement efforts in the Coral Triangle region. The findings are consistent with those of the literature on compliance and enforcement that any compliance and enforcement system must not only use deterrence, but also be perceived by fishers as being legitimate, fair, accountable and equitable and the need for developing a personal morality and a social environment that supports compliance. There is an opportunity to strategically build on shared value and cultural norms that can promote collaborative fisheries management as a mechanism to increase compliance through non-coercive efforts. Strengthening the long-term capacity for consistent delivery of local support to marine management and enforcement will increase local compliance rates through time.     

加拿大的城市轨道交通技术

加拿大幅员辽阔,但人口稀少(大约3000万人).由于气候地理的原因,90%的加拿大人居住在与美国邻界322 km宽的窄带内.另外,加拿大的大多数人,确切地说是76.6%,居住在城市和城镇,只有23.4%的人居住在乡村.因此,加拿大的城市发展问题十分重要.多伦多、蒙特利尔、卡尔加里、温哥华等城市已发展成为国际大都市,多种经济形式并存,服务业十分发达,还有银行、工程、医药和科学研究等.     

A model of traffic dispersion from a congested road

The study of traffic flow dynamics is developed by defining and clarifying traffic divergence, continuity, congestion and dispersion. Velocity potential is introduced as a gravity function generated by the interaction of two or more motorists occupying neighbouring points in space and describes interference to continuous traffic flow. The relationship between the potential function and carrying capacity is developed and dispersion, when considered as a random walk, satisfies a diffusion equation. A model of traffic dispersion along a maximum congested road in space and time is presented as eigenfunctions of the velocity potential. This suggests that traffic can be dispersed by a series of quantum steps. A probability density function is introduced to define the probability of locating a motorist in a congestion zone.     

Strategic alliances in the container shipping industry: a global perspective

This paper examines developments in container shipping in light of the formation of strategic alliances by many of the leading companies. It focuses on three features: the transformation of services, the evolution of the fleet, and the adjustments made to the ports of call. These elements are analysed on a global basis for 3 years: 1989, 1994 and 1999. Some of the changes wrought by the alliances are identified, including the spread and intensification of services, and the deployment of the largest vessels on alliance routes. While the individual companies that have come together in alliances are serving many more ports than before, it is also demonstrated that the total number of ports served by the industry has remained constant. The results are interpreted in the context of globalization that is tending to impose greater standardization on the container shipping industry.     

Integrated Marine Planning for Cocos (Keeling), An Isolated Australian Atoll (Indian Ocean)

The Cocos (Keeling) Islands are located on an isolated atoll in the Indian Ocean and have a strong Malay culture owing to the translocation of a substantial plantation workforce in the early 19th century. The atoll became one of Australia's External Territories in 1955. Meeting the marine resource needs of the atoll residents within an Australian legislative system by formulating an integrated marine management plan presented several challenges. Key factors in drafting a culturally meaningful plan were a commitment to understanding and accommodating the cultural and subsistence needs of the community, innovative communication strategies, and a simple approach to management. Development of the plan highlighted the limitations of current Australian marine planning legislation in cross-cultural settings and for sustainable development.     

Valuing Estuarine Resource Services Using Economic and Ecological Models: The Peconic Estuary System Study

This article summarizes four integrated economic studies undertaken to contribute to resource preservation and restoration decisions for the Peconic Estuary System of Suffolk County, NY. Completed as part of the National Estuary Program, the studies apply distinct resource valuation methods to a wide range of resource issues. The principal goals of this article are to highlight different methodologies that may be used to assess nonmarket economic values in a coastal management context, and characterize differences in the results that one may expect from each approach. We also emphasize potential relationships among values estimated by different nonmarket methodologies, and comment on the implications of these relationships for the interpretation and use of economic value estimates.     

Research review of air traffic management

As air transport demand keeps growing more quickly than system capacity, efficient and effective management of system capacity becomes essential to the operation of the future global air traffic system. Although research in the past two decades has made significant progress in relevant research fields, e.g. air traffic flow management and airport capacity modelling, research loopholes in air traffic management still exist and links between different research areas are required to enhance the system performance of air traffic management. Hence, the objective of this paper is to review systematically current research in the literature about the issue of air traffic management to prioritize productive research areas. Papers about air traffic management are discussed and categorized into two levels: system and airport. The system level of air transport research includes two main topics: air traffic flow management and airspace research. On the airport level, research topics are: airport capacity, airport facility utilization, aircraft operations in the airport terminal manoeuvring area as well as aircraft ground operations research. Potential research interests to focus on in the future are the integration between airspace capacity and airport capacity, the establishment of airport information systems to use airport capacity better, and the improvement in flight schedule planning to improve the reliability of schedule implementation.     

Mobility evaluation for urban public transportation

Summary

This paper has reported on a study of relative opportunity—not absolute opportunity. Minimum absolute standards for mobility or accessibility are difficult to justify. Some additional study into the development and application of absolute mobility standards may be warranted.

The application of the mobility evaluation model has primarily focused upon a corridor line‐haul system. Conclusions suggest that such a system will not markedly improve existing transit mobility levels in either the peak hour or the off‐peak. The experimental work has verified this conclusion, and more importantly, it has detailed quantitatively the exact levels and spatial distribution of mobility improvements. However, this study does not include a comprehensive analysis of all methods of mobility enhancement, nor does it undertake a comparison of alternative means of mobility improvement. Certainly other methods to improve access to opportunities should be explored before policy considerations are finalized. These methods include other transit solutions, land use alternatives, socio‐economic policies, and other‐mode transportation alternatives. The accessibility technique and mobility indices approach appears to have general applicability in the analysis of optimal strategies for system evaluation.

Of interest is an examination of alternative feeder transit systems to the corridor line. Additional research with the model might point out the maximum mobility effects expected through improved collector service in the suburbs, with corridor line‐haul to the CBD.

The indices are also readily available for a comparison of mobility patterns for different urban areas. Application of the program to transit and socio‐economic data for a set of cities would yield an indication of the relative mobility levels provided. Such data might be considered as an evaluation criterion for future transit funding by federal officials.

In addition, the model is currently being considered by UMTA as a tool to aid in the evaluation of the equitable distribution of transit system benefits as defined in Title VI of the Civil Rights Act of 1964.²⁵ The mobility output would serve as an indicator of the levels‐of‐service provided to certain disadvantaged urban groups. For this application the computer model is being altered to achieve compatability with the Transportation Planning System (UTPS) computer model package developed by UMTA.     

Development of a neighborhood commute mode share model using nationally-available data

Transportation - Practitioners often use demand models to predict how neighborhood-level land use, infrastructure, demographic, and other changes may impact transportation systems. Few of the...