A porous cell method for the simulation of fluid-solid interactions

There are many ways of describing a solid,porous or fluid region of the computational domain when solving the Navier-Stokes equations(NSE)for flow motions.Amongst these the porous cell method is one of the most flexible approaches.In this method,a parameter is defined as a ratio of the volume open to water and air in a calculation cell to its cell volume.In the calculation,the same numerical procedure is applied to every cell and no explicit boundary conditions are needed at solid boundaries.The method is used to simulate flow through porous media,around solid bodies and over a moving seabed.The results compare well with experimental data and other numerical results.In our future work the porous cell method will be applied to more complex fluid-solid interaction situations.     

Optimal transport strategies for European cities

A new procedure for generating optimal transport strategies has been applied in nine European cities. A public sector objective function which reflects concerns over efficiency, environmental impact, finance and sustainability is specified and a set of policy measures with acceptable ranges on each, identified. Optimal strategies based on combinations of these policy measures which generate the optimal value of the objective function, are identified, and compared between cities. Resulting policy recommendations are presented. The results demonstrate the importance of an integrated approach to transport strategy formulation. They emphasise the role of changes in public transport service levels and of fares, and of charges for car use. By contrast, new infrastructure projects are less frequently justified. In the majority of cities the revenues from car use charges are sufficient to finance other elements in the strategy. However, private sector involvement either in initial financing or in operation may be desirable. Revised objective functions to reflect private sector involvement are specified, and optimal strategies with private sector operation of public transport are also identified. The requirement to meet private sector rates of return for public transport operation typically results in lower frequencies and higher fares; charges for car use then need to be raised to satisfy public policy objectives, but system performance is reduced. This revised version was published online in June 2006 with corrections to the Cover Date.     

Transportation mode choice and city-suburban public transportation service

A model is presented to describe the dynamics of transportation mode choice in which the interaction between transportation users and a public transportation authority results in self-organization. The model illustrates that a sufficient number of connections between a central city and its suburbs are required for self-organization to occur whereby public transportation use and service will grow.     

Optimal Design of Running Gears Part II. Applications

In the second part of the paper applications are shown for the two-axle unsymmetric running gear and for symmetric running gears with two, three and four wheelsets.     

Monitoring urban spatial dynamics

As urban systems increase in size and diversity, the factors which influence spatial change increase in number and their interactions become more complex. Increasing emphasis is thus being placed by some governments and agencies on regular reviews of policies and programs, to ensure that they are consistent with and facilitate the evolving urban form. Consequently, the monitoring of urban transport and activity systems is of increasing importance, to aid the review processes. This paper considers the progress which has been made in and use of procedures for monitoring urban, transport-related spatial changes. The specification, estimation and presentation of appropriate indicators is briefly discussed. Experience with the use of spatial monitoring procedures on data for two Australian cities has revealed several possible implications for transport investment practice and the development of monitoring and modelling procedures. These are discussed and the paper then indicates the approach which is currently being taken at ARRB towards developing a monitoring system.     

Level crossing safety on East Japan Railway Company: Application of probabilistic risk assessment techniques

This paper describes the application of probabilistic risk assessment techniques to level crossing safety on JR East, the largest of the six private railroads in Japan. The risk of a level crossing accident was defined as the product of the accident rate and the expected consequences per accident. Rail traffic volume, road traffic volume, visibility of the crossing from the road, road gradient, width of the crossing and the type of safety devices at the crossing were shown to influence the accident rate and the collective risk. The mean accident rate at all crossings was 0.74 per million trains. The accident rate was 0.59 per million trains at crossings equipped with barriers, 1.25 at crossings equipped with warning bells and 0.76 at pedestrian crossings. Crossings equipped with obstacle detectors had a lower accident rate (0.12 per million trains) than crossings without detectors (0.43 per million trains). Crossings with visibility less than 20 m had a 50% higher mean accident rate than crossings with visibility greater than 20 m. As the number of tracks increased, the accident rate monotonically increased due to the increased accident exposure. Risk assessment techniques were applied to determine the efficacy of the various level crossing safety devices. In addition to upgrading the safety of crossings, the management techniques stressed the importance of education campaigns in warning the public about the dangers of illegal crossings.