The punctuality performance of aircraft rotations in a network of airports

The aim of this paper is to investigate the influence of aircraft turnaround performance at airports on the schedule punctuality of aircraft rotations in a network of airports. A mathematical model is applied, composed of two sub-models, namely the aircraft turnaround model (turnaround simulations) and the enroute model (enroute flight time simulations). A Markovian type model is featured in the aircraft turnaround model to simulate the operation of aircraft turnarounds at an airport by considering operational uncertainties and schedule punctuality variance. In addition, stochastic Monte Carlo simulations are employed to carry out stochastic sampling and simulations in both the aircraft turnaround model and the enroute model. Results of simulations show the robustness of the aircraft rotation model in capturing uncertainties from aircraft rotations. The propagation of knock-on delays in aircraft rotations is found to be significant when the short-connection-time policy is used by an airline at its hub airport. It is also found that the proper inclusion of schedule buffer time in the aircraft rotation schedule helps control the propagation of knock-on delays and, therefore, stabilize the punctuality performance of aircraft rotations.     

The role of VMT reduction in meeting climate change policy goals

This article evaluates the case for vehicle miles traveled (VMT) reduction as a core policy goal for reducing greenhouse gases (GHGs), concluding the economic impacts and social consequences would be too severe given the modest potential environmental benefits. Attempts to reduce VMT typically rely on very blunt policy instruments, such as increasing urban densities, and run the risk of reducing mobility, reducing access to jobs, and narrowing the range of housing choice. VMT reduction, in fact, is an inherently blunt policy instrument because it relies almost exclusively on changing human behavior and settlement patterns to increase transit use and reduce automobile travel rather than directly target GHGs. It also uses long-term strategies with highly uncertain effects on GHGs based on current research. Not surprisingly, VMT reduction strategies often rank among the most costly and least efficient options. In contrast, less intrusive policy approaches such as improved fuel efficiency and traffic signal optimization are more likely to directly reduce GHGs than behavioral approaches such as increasing urban densities to promote higher public transit usage. As a general principle, policymakers should begin addressing policy concerns using the least intrusive and costly approaches first. Climate change policy should focus on directly targeting greenhouse gas emissions (e.g., through a carbon tax) rather than using the blunt instrument of VMT reduction to preserve the economic and social benefits of mobility in modern, service-based economies. Targeted responses are also more cost effective, implying that the social welfare costs of climate change policy will be smaller than using broad-brushed approaches that directly attempt to influence living patterns and travel behavior.     

DISCREPANCY OF COCAINE EFFECT ON CONDUCTION AND REPOLARIZATION

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Congestion relief toll tunnels

Changing urban land-use patterns have reduced the importance of traditional downtowns as the origin and destination of numerous vehicular trips. Much traffic on downtown-area freeways seeks merely to get past downtown, thereby worsening the level of congestion for those seeking access to downtown.A number of European cities have begun to develop a new type of transportation facility: congestion-relief toll tunnels in downtown areas. These projects appear to be economically feasible largely or entirely from premium-price tolls paid by users. Hence, they are being developed by private consortia, operating under long-term franchises from government. Other keys to the feasibility of such projects are peak/off-peak pricing structures (congestion pricing), nonstop electronic toll collection, and restriction of use to auto-size vehicles only (to reduce tunnel dimensions and therefore capital investment).Preliminary analysis indicates that congestion-telief bypass runnels for downtown Los Angeles and San Francisco would be economically feasible as private business ventures, if developed along European lines. Similar approaches might be applied to other controversial freeway projects in both cities, and to restructuring Boston's huge and controversial Central Artery/Tunnel project.Congress has already authorized public-private partnerships of this type, permitting private capital and private owner/operation to be used, both for new projects and to rebuild existing highway, bridge, and tunnel facilities. Six states and Puerto Rico have enacted private-tollway legislation under which such projects could be developed and operated.This type of project should be politically feasible, since it offers a way to make significant transportation improvements in impacted downtowns with little or no public funding. While transit proponents may oppose the construction of toll tunnels, highway users are likely to support such projects, and some environmental groups may support this method of implementing congestion pricing in urban areas, because of its potential for reducing air emissions.     

Jack-up conversion for production

For the production development of marginal offshore oil fields or to achieve early production in offshore fields scheduled for full production facilities a jack-up drilling rig can be converted to operate as a mobile production unit. This paper presents a summary discussion of the main aspects to be considered in the design, conversion, installation and operation of a jack-up production unit.     

A note on Norske Ø Ice Barrier (Northeast greenland), viewed by landsat 5 TM

The structure and nature of Norske Ø Ice Barrier, the southern boundary of the Northeast Water summer polynya, is deduced from Landsat 5 TM images. Within the barrier, three main areas are identified: glaciers to the west, a permanent central ice region made up of fast ice and a variable zone of attached pack ice.     

The Caribbean basin: adjusting to global trends in containerization

Positioned strategically between major east-west and north-south trading routes, the Caribbean basin has become a locus of new service configurations in container shipping. Over the last decade global shipping lines have been restructuring their service networks in the region in order to integrate local services with the newly rationalized intercontinental connections. By comparing service network structures in 1994 and 2002 at three levels of organization—local, regional and global—we are able to show that although Caribbean ports are well connected to the global system, and while the total number of services has declined between the two years, those mounted by members of global alliances have increased. Moreover, services of the global carriers at the local and regional levels are on the increase. As much as the alliances are reshaping Caribbean networks, the smaller carriers are still playing a role, but at a reduced spatial scale. Parallel with the modifications to network configurations are the changes in the port system. Essentially, traffic of the most important ports in the north and western part of the basin has grown at slower rates than the ports in the south and east. These traffic changes are only partly related to network changes. It is the growth of transshipments that is driving the most important developments in port traffic and bringing to the forefront the development of hub ports. The most important are: Colon, Panama (southwest), Freeport, Bahamas (north), Port of Spain, Trinidad and Tobago (southeast), Kingston, Jamaica and Rio Haina, Dominican Republic (middle), and Cartagena, Colombia and Puerto Cabello, Venezuela (south).     

A multiobjective hierarchical model for locating public facilities on a transportation network: A goal programming approach

This paper introduces a Multiobjective Hierarchical Model (MOHLM) for locating public facilities on a transportation network. The proposed model combines the multiobjective nature of the location-allocation problem with the hierarchical character of some public service systems, such as health care delivery. The model examines both maximum and total weighted travel time, facility utilization, and total travel time from the master facility to the attached subordinate facilities. An iterative goal programing algorithm is used to solve the problem. An example related to the location of health care facilities in a rural area of Greece is used to illustrate the application of the proposed model.     

Introducing congestion pricing on a new toll road

This paper proposes a demonstration project to test the effectiveness of congestion pricing in an urban area. It reviews the general theoretical case for such pricing and summarizes recent international interest in congestion pricing. Next, it sets forth the reasons why demonstration projects are needed, both to add to our knowledge about how effective congestion pricing may prove to be, and to address political and other public-acceptance barriers to implementation of the concept. The paper then defines a specific proposed test site for congestion pricing: a new toll road being planned for Orange County, California. It is proposed that instead of charging flat-rate tolls, the transportation agency could charge peak and off-peak tolls, increasing the level of the peak charge each year over a period of up to 10 years unless or until toll revenues decline below the levels forecast under the flat-rate toll alternative. Measurements of traffic flow and ride-sharing behavior would be made, as well as calculations of emission-reduction effects. The paper concludes with a brief discussion of marketing and political considerations involved in conducting such a demonstration.Abbreviations ARB Air Resources Board - AVI Automatic Vehicle Identification - CDMG Corridor Design Management Group - HOV High-occupancy vehicle - SJHTC San Joaquin Hills Transportation Corridor - TCA Transportation Corridor Agency - VMT Vehicle miles traveled