Transportation Research Part A: General最新文献

This article investigates the macroscopic lane-changing characteristics on uncongested multilane freeways, focusing on the interrelations between the traffic conditions and the frequency (and fraction) of vehicles changing lanes. The data available for analyses were collected from two test sites using a time-elapsed video recorder. It has been found that traffic flow variables, such as the headway mean and variance, speed, and density ratios between neighboring lanes, are highly correlated with the fraction and frequency of vehicles changing lanes. The results of exploratory analyses are further examined with two generalized linear models. The logistic and Poisson regressions are used respectively for constructing the lane-changing fraction and frequency models. With maximum likelihood estimation (MLE) both models provide consistent information and achieve a reasonable goodness of fit.

Truck class rates are usually needed in strategic logistical planning, especially for facility location. Using point-to-point transport rates is exact, but for practical reasons it is often necessary to estimate them from distance. Two sources of rate estimating error are examined: (a) the error resulting from the linear approximation of rates from distances; and, (b) the error associated with estimating distances from shipment origin-destination coordinate points. Suggestions are made as to how the rate estimating error may be minimized.

Railroad technology permits a single train to move a large number of individual freight cars. However, cars which are not in dedicated unit train or intermodal service experience considerable delay due to the consolidation and breakup of trains. Rail operations thus involve a tradeoff between the economies of shipment consolidation, and the resulting delays. More direct and/or more frequent train connections will increase costs, but reduce transit times. This article quantifies the cost of providing a range of transit times for general carload traffic for several representative U.S. rail systems. It shows that significant reductions in transit time will require a large increase in the number of train connections and operating cost. Changes in labor contracts to reduce train crew cost will provide some incentive for higher service levels, but reductions in crew cost alone cannot be expected to dramatically improve the performance of the carload segment of the industry.

This paper presents an analysis of the instability phenomenon on motorways, with aim of arriving at the definition of a control strategy suitable for keeping the flow stable. By using some results of the motorway reliability theory, a relationship between reliability and some flow characteristics is obtained, which shows the existence of a reliability threshold critical for flow stability. The macroscopic flow characteristics corresponding to this threshold are very different in different situations, so that the control of flow stability requires the analysis of speed and time gap microscopic processes surveved on a cross section of the motorway carriageways to be controlled. A method is presented, based on the analysis in real time of these processes, by which it is possible to detect the approach of instability before its effects become manifest, and to single out the proper control strategy in different situations.

The main deficiency of most current modeling approaches to transportation can be identified as neglect of the integration of existing geographical knowledge in regard to the ex ante transport/land use modeling approaches, with its focus on territorial dynamics and theory development. This paper addresses this aspect of the problem by introducing a theoretical and methodological framework for the analysis of the interrelationship between land uses. The analysis attempts to determine to what extent the functional land use in a city can be considered an ordered pattern. The order sought does not rely on purely spatial configurations, but on the correlation of transportation and land use. The first section of this paper focuses on theoretical considerations. It stresses the fact that conventional approaches do not apply in the present context. It then suggests an alternative based on areas of influence and measured in terms of level of attractance of land uses. The second describes a procedure based on this alternative following the remarkable contribution of Hanjoul, Beguin and Thill. An application of this procedure to the analysis of Shanghai is then examined. Finally, an evaluation of the strategies for optimizing the interrelationship between land uses is presented. The paper concludes with a possible research agenda.

The objective of this article is to establish whether the train has a role to play in the market for intercity passenger travel in the United States. To accomplish this objective, we compare the common carriers on the basis of thier cost effectiveness in moving a given flow of passengers between two points a specified distance apart. The comparisons are based on cost models which highlight the technological differences between the modes and eliminate distortions caused by public policy choices. By varying the size of the passenger flow and trip distance, we develop a notion of each common carrier's ideal operating environment. We find that the cost of the right-of-way is the major factor limiting the range of travel situations in which the train is cost competitive with the other common carriers. More specifically, our results indicate that Amtrak's service in the Northeast Corridor should be continued in the short run. In the long run, the possibility of upgrading Amtrak's service in the Northeast Corridor to high-speed service should be investigated. Outside the Northeast Corridor, we find that high-speed train service should be able to cover its operating costs but not its capital costs.