Transportation Research Part A: General最新文献

Developing countries have lost billions of dollars during the last decade due to the deterioration of their roads. The macroeconomic losses caused by the lack of adequate road maintenance could be avoided by improving maintenance practices. This paper describes a method to analyze and improve present road maintenance practices in developing countries, referring to a recently conducted study in Nepal. Road maintenance is understood to be not just a technical problem, but rather a complex system with various elements. Therefore, road maintenance problems have to be tackled with different approaches on different levels. Proceeding from the existing system deficiencies, or “problem areas,” and on the basis of a hierarchy of instrumental objectives, the development of measures and projects suited to improve road maintenance practices is described. The application of a standardized evaluation scheme can support governments and development organizations in choosing promising measures in this field.

This paper presents a model that systematically integrates, for the first time, the association between a region's aviation near-midair collision risk and its traffic levels, its type and amount of air traffic control, and the complexity of its airspace. The model incorporates the tight interrelatedness (and correlation) between traffic, airspace complexity, and air traffic controller staffing. An estimation of the model using cross-sectional data on 143 U.S. airports in 1985 indicates that the frequency of reported near-midair collisions (NMACs) is positively associated with regional traffic and airspace complexity, despite the fact that busier, more complex regions generally have more air traffic controllers. Also, in regions governed by “terminal radar service areas” (TRSAs), the reported near-midair collisions are positively associated with the presence of more satellite airports than would be expected on the basis of traffic alone. Finally, deviations from controller staffing levels that would be expected on the basis of traffic and airspace complexity alone are significantly associated with variations in reported NMACs in terminal control areas but not in terminal radar service areas.

This paper presents the results of a large sample survey designed to investigate the response of commuters to the delivery of traffic information. The main purpose of the survey was to investigate the impact of traffic information on commuters route choices, mode choices, and departure times in order to provide functional requirements for the design of a real-time motorist information system. The surveyed population consisted of 3,893 freeway motorists who routinely commuted to a central business district. The results of the survey indicated that four distinct commuter subgroups existed with respect to their traffic information needs: These groups were: (1) route changers, those willing to change route, or mode before entering the freeway (20.6%), (2) nonchangers, those unwilling to change time, route, or mode (23.4%), (3) time and route changers, (40.1%), and (4) pretrip changers, those willing to change time, mode, or route before leaving the house (15.9%). In terms of receiving traffic information, commercial radio was rated as the most useful and preferred medium both before and while driving. However, only a small, discrete group of commuters were likely to be influenced to change transportation mode. Implication of the survey results for the design of a real-time motorist information system are discussed.

A methodology is proposed for sequencing and scheduling of aircraft in high density terminal areas. Termed Constrained Position Shifting (CPS), this methodology is examined and its effectiveness tested. Potential capacity improvements are noted over the First-Come, First-Served, Runway (FCFS-RW) strategy, especially during peak periods.

This research addresses the need to estimate the demand for scheduled commercial passenger service in small communities. Data were collected describing the social, economic, and geographic characteristics of 260 small communities in the contiguous 48 United States, with airports enplaning at least 2,500 passengers in 1985. Small communities were defined as those with service area populations of 200,000 or less. Descriptive data included population, income, labor force characteristics, community economic base, geographic location, departures, air fare per mile, driving distance to an alternative airport, and the attractiveness of driving to an alternative airport. A methodology for selecting the most probable alternative airport when choices are present is included. Multiple regression models were specified with the data collected to estimate enplanements. The best model explained 80% of the variation in the data. The model was demonstrated by estimating the demand for air service at 52 small communities in the state of Texas. The methodology was designed to be easily applied in the field. Only readily available U.S. Census Bureau and Official Airline Guide data are required.

This paper presents the results of a study that evaluated the contribution of manual operation (by a police officer) compared to the automatic control of an actuated signal. It is shown that manual operation improved the operation of congested signalized intersections, as measured by the degree of saturation and total throughput. It is found that the major advantage of manual control is due to the use of long cycle times, resulting in a decrease in lost time during congestion. It is argued that such a strategy can be successfully implemented as part of the automatic control. Measurements have indicated a significant decline in the saturation flow with the increase in the green period. The paper describes the phenomenon and its importance to intersection capacity.