A reliability‐based network design problem

This paper presents a reliability‐based network design problem. A network reliability concept is embedded into the continuous network design problem in which travelers' route choice behavior follows the stochastic user equilibrium assumption. A new capacity‐reliability index is introduced to measure the probability that all of the network links are operated below their capacities when serving different traffic patterns deviating from the average condition. The reliability‐based network design problem is formulated as a bi‐level program in which the lower level sub‐program is the probit‐based stochastic user equilibrium problem and the upper level sub‐program is the maximization of the new capacity reliability index. The lower level sub‐program is solved by a variant of the method of successive averages using the exponential average to represent the learning process of network users on a daily basis that results in the daily variation of traffic‐flow pattern, and Monte Carlo stochastic loading. The upper level sub‐program is tackled by means of genetic algorithms. A numerical example is used to demonstrate the concept of the proposed framework.     

Some Basic Properties of Bogies, an Analytical Approach

An important function of a bogie of a railway vehicle (or of the running gear of guided vehicles in general) is to guide or steer the vehicle along the course of the track while isolating the vehicle and its payload as well as possible from unintended but inevitable imperfections in the position of the track. Against this background, an analytical expression is derived for the low speed transfer function of a bogie, from which conclusions can be drawn regarding the effect of the elastic connections between wheelsets on dynamic behaviour. At higher speeds inertia effects of the unsprung masses have a negative effect on dynamic behaviour, the magnitude of this effect being different for different types of elastic connections. This is also reflected in the critical speed and the interaction between body and bogie. With respect to the wear of wheels and rails on curved track, the range of radii of curves which can be traversed without flange contact and, for smaller radii, the rate of increase of flange force and angle of attack of the leading wheelset are important factors. Some expressions are derived for the effect of the elastic connections between wheelsets on these factors.     

Priorities in urban transport research

Research should be fundamental to transportation as a phenomenon, and yet central to the problems that need to be solved. This paper looks at the history of transportation research in the U.S. with a view toward understanding the bases of past research priorities, and deriving a basis for proposing future priorities. As a result, varieties of research are proposed. They include research which is progressive by criteria of the field during past decades, research which is critical or established as needed by rejection of those criteria, and research which arises as newly required by recent mandates to the field. As the most significant conclusion, it is proposed that research models be built — models which put the understanding of urban structure dynamics ahead of accuracy in forecasting.The authors wish to acknowledge the assistance of Ray Blessing, Department of Urban Studies and Planning, and Thomas McKim, Department of Civil Engineering, M.I.T. This paper has profited from criticism by Professor Daniel Brand. The original version was prepared with support from the National Science Foundation.     

Dynamic Interaction between Wheel and Track - A Parametric Search towards an Optimal Design of Rail Structures

The dynamic vertical interaction between a moving rigid wheel and a flexible railway track is investigated. A round and smooth wheel tread and an initially straight and noncorrugated rail surface are assumed in the present optimization study. A symmetric linear three-dimensional beam structure model of a finite portion of the track is suggested including rail, pads, sleepers and ballast with spatially nonproportional damping. The full interaction problem is numerically solved by use of an extended state-space vector approach in conjunction with a complex modal superposition for the track. Transient bending stresses in sleepers and rail are calculated. The influence of seven selected track parameters on the dynamic behaviour of the track is investigated. A two-level fractional factorial design method is used in the search for a combination of numerical levels of these parameters making the maximum bending stresses a minimum.     

Citizen participation through communicative action: Towards a new framework and synthesis

The record of public involvement in the transportation planning process in the United States has been uneven and, at times, disappointing. It is therefore a matter of some satisfaction that the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA), recognizes that public involvement and input is essential in transportation plan-making. However, little guidance is available to planners as to how participatory democracy could possibly be enhanced and improved in the existing transportation planning process. As matters stand today, the predominant use of technical rationality in the planning process, to the exclusion of communicative action, has probably been the biggest problem. This paper introduces the concepts of communicative action to buttress and complement technical rationality, currently used in the transportation planning process. A real-life case-study is presented to demonstrate how communicative action was successfully used in a problem-ridden planning situation. Validity claims as suggested by Habermas in his Theory of Communicative Action are used in this case-study. It is concluded that academic institutions as well as planning agencies will have to make a concerted effort to educate and train planners not only to be involved with the engineering of our infrastructure, but also to be equally concerned with coping with the social, economic and political dimensions of planning.