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871.
In this paper, a method for designing a statistically valid sample of bridges is proposed. The need for such a sampling procedure arises from the impracticality of a detailed analysis of the structural effects of new candidate truck configurations on the whole bridge inventory. In this study, a set of bridges from the national inventory was determined for the purpose of selecting a bridge sample. This set of bridges is referred to as the population. The selection of bridges for inclusion in the population was based on the status of the bridge, type of service, structural material, structural system type and functional class. The stratified sampling method was used in the determination of the required sample sizes. According to this method, the population was first divided into sub-populations, or strata. These sub-populations were non-overlapping. In turn, each strata was divided into sub-strata. The characteristics of each sub-stratum were estimated and combined to determine the characterics of the strata. Then the characteristics of the strata were combined to determine the characteristics of the bridge population. A comparison of the results based on the sample and bridge population was conducted in order to verify the validity of the proposed sampling procedure. 相似文献
872.
S. R. C. Wanhill 《Maritime Policy and Management》1978,5(4):315-326
This paper outlines the theoretical background to port-investment projects and compares this with current practice. 相似文献
873.
This paper provides a framework for assessing the progress that is being made in the computer-assisted dispatching of trains. The state of the art is described in general terms, and future research needs are identified. 相似文献
874.
875.
This paper looks at the relationships between ship size, handling rate and ship berth time for five major ports in the United Kingdom. The results show that there is no simple linear relationship between these variables. The causes and implications of this are discussed. 相似文献
876.
877.
This article presents the economic rationale for road pricing and provides some scale on the magnitude of peak period tolls that might be justified. It discusses the impacts of such tolls on congestion, air quality and economic development and suggests a long term strategy towards areawide implementation of peak period pricing. It discusses current trends which are increasing the likelihood for implementation of congestion pricing and toll roads in the future. In particular, it discusses some aspects of the 1991 Intermodal Surface Transportation Efficiency Act (ISTEA) which will eliminate some of the current restraints on congestion pricing and toll highways.Abbreviations ETC
Electronic toll collection
- FHWA
Federal Highway Administration
- HOV
High occupancy vehicle
- ISTEA
Intermodal Surface Transportation Efficiency Act
- LOS
Level of service
- TCM
Transportation control measure
- V/C
Volume-to-capacity ratio
- VMT
Vehicle mile(s) of travel
- vphpl
Vehicles per hour per lane 相似文献
878.
879.
R. C. Redfield D. C. Karnopp 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1988,17(5):231-253
Most vehicle suspension systems use fixed passive components that offer a compromise in performance between sprung mass isolation, suspension travel, and tireroad contact force. Recently, systems with discretely adjustable dampers and air springs been added to production vehicles. Active and semi-active damping concepts for vehicle suspensions have also been studied theoretically and with physical prototypes. This paper examines the optimal performance comparisons of variable component suspensions, including active damping and full-state feedback, for “quartercar” heave models. Two and three dimensional optimizations are computed using performance indicators to find the component parameters (control gains) that provide “optimal” performance for statistically described roadway inputs. The effects of performance weighting and feedback configuration are examined. Active damping is shown to be mainly important for vehicle isolation. A passive vehicle suspension can control suspension travel and tire contact force nearly as well as a full state feedback control strategy. 相似文献
880.
A major research study funded by the UK Overseas Development Administration (ODA) and designed to establish the necessary considerations for viability of mass rapid transit railways in developing cities was recently completed. The analytical core of the study was a pre-appraisal model, which combines an innovative strategic land use/transport model utilizing relationships from developing cities and an economic evaluation model. This model — MRTAP — has now been developed into a user-friendly package which the ODA intend should be made widely available in the developing world. The paper describes the basis of this model. 相似文献