A virtual environment for the formulation of policy packages

The interdependence and complexity of socio-technical systems and availability of a wide variety of policy measures to address policy problems make the process of policy formulation difficult. In order to formulate sustainable and efficient transport policies, development of new tools and techniques is necessary. One of the approaches gaining ground is policy packaging, which shifts focus from implementation of individual policy measures to implementation of combinations of measures with the aim of increasing efficiency and effectiveness of policy interventions by increasing synergies and reducing potential contradictions among policy measures. In this paper, we describe the development of a virtual environment for the exploration and analysis of different configurations of policy measures in order to build policy packages. By developing systematic approaches it is possible to examine more alternatives at a greater depth, decrease the time required for the overall analysis, provide real-time assessment and feedback on the effect of changes in the configurations, and ultimately form more effective policies. The results from this research demonstrate the usefulness of computational approaches in addressing the complexity inherent in the formulation of policy packages. This new approach has been applied to the formulation of policies to advance sustainable transportation.     

Application of advanced sampling for efficient probabilistic traffic modelling

In probabilistic traffic models, consideration of stochasticity in the dynamics of traffic gives a closer representation of a traffic system in comparison to that of a deterministic approach. Monte Carlo simulation is a broadly accepted method to consider variations in traffic within modelling. In this contribution, the possibility of increasing the efficiency of probabilistic traffic flow models using Monte Carlo simulation is analysed using variance reduction techniques and sequencing, for varied capacity and traffic demand values. The techniques of Importance Sampling, Latin Hypercube Sampling and Quasi-Random Sequencing are compared in a dynamic macroscopic traffic model to demonstrate the effectiveness of these techniques for reduction of the computational load when considering multiple input variations. Demonstration of their efficiency in traffic modelling is expected to lead to a wider application of the methods in practice.     

Truck parking in urban areas: Application of choice modelling within traffic microsimulation

Urban truck parking policies include time restrictions, pricing policies, space management and enforcement. This paper develops a method for investigating the potential impact of truck parking policy in urban areas. An econometric parking choice model is developed that accounts for parking type and location. A traffic simulation module is developed that incorporates the parking choice model to select suitable parking facilities/locations. The models are demonstrated to evaluate the impact of dedicating on-street parking in a busy street system in the Toronto CBD. The results of the study show lower mean searching time for freight vehicles when some streets are reserved for freight parking, accompanied by higher search and walking times for passenger vehicles.     

Modelling and validation of coupled high-speed maglev train-and-viaduct systems considering support flexibility

This study presents a more realistic modelling of the maglev-based high-speed railway line in Shanghai, China. Focus is placed on an accurate simulation of the two subsystems: the train subsystem including the magnets and the viaduct subsystem including the modular function units of the rails. The electromagnet force–air gap model with a proportional-derivative (PD) controller is adopted to simulate the interaction between the maglev train via its electromagnets and the viaduct via its modular function units. The flexibilities of the rails, girders, piers and associated elastic bearings are all considered in the modelling of the viaduct subsystem to investigate their effects on an interaction between the two subsystems. By applying the proposed model to the Shanghai maglev line, the essential characteristics of the coupled system can be duly captured. The accuracy and effectiveness of the proposed approach are then validated by comparing the computed dynamic responses and frequencies with the measurement results. It is confirmed that the proposed modelling with a detailed simulation of the magnets and modular function units can duly account for the dynamic interaction between the train and viaduct systems. Moreover, the effects of the inclusion of the flexibilities of the rails, girders and elastic supports to the response of the coupled system are respectively investigated, the results of which prove that their involvements are essential to the accurate prediction of the response of the coupled maglev train–viaduct system.     

Validation of vehicle dynamics simulation models – a review

In this work, a literature survey on the validation of vehicle dynamics simulation models is presented. Estimating the dynamic responses of existing or proposed vehicles has a wide array of applications in the development of vehicle technologies, e.g. active suspensions, controller design, driver assistance systems, etc. Although simulation environments, measurement tools and mathematical theories on vehicle dynamics are well established, the methodical link between the experimental test data and validity analysis of the simulation model is still lacking. This report presents different views on the definition of validation, and its usage in vehicle dynamics simulation models.     

Efficient empirical modelling of a high-performance shock absorber for vehicle dynamics studies

This paper develops an intuitive empirical nonlinear dynamic shock absorber model for simulation studies. Unlike other existing dynamic shock absorber models, it does not suffer from the complexity of modelling complex physical behaviour, or the inefficiencies of unstructured black-box modelling. The model consists of an algebraic backbone, which is a function of velocity alone, and a nonlinear low-pass filter, which has been designed based on the observation that the damper can respond more quickly at higher velocities. Due to the simplicity of the model, it can be fitted with data and evaluated quickly. The model was fitted using shock dynamometer test data using a random shock position command. The completed model is then validated using random, sine wave, and bump test data. This analysis shows the strengths and weaknesses of the model and suggests areas for future development.     

A review of dynamics modelling of friction wedge suspensions

Three-piece bogies with friction wedge suspensions are the most widely used bogies in heavy haul trains. Fiction wedge suspensions play a key role in these wagon systems. This article reviews current techniques in dynamic modelling of friction wedge suspension with various motivations: to improve dynamic models of friction wedge suspensions so as to improve general wagon dynamics simulations; to seek better friction wedge suspension models for wagon stability assessments in complex train systems; to improve the modelling of other friction devices, such as friction draft gear. Relevant theories and friction wedge suspension models developed by using commercial simulation packages and in-house simulation packages are reviewed.     

Tyre-force estimation by Kalman inverse filtering: applications to off-highway mining trucks

Kalman inverse filtering is used to develop a methodology for real-time estimation of forces acting at the interface between tyre and road on large off-highway mining trucks. The system model formulated is capable of estimating the three components of tyre-force at each wheel of the truck using a practical set of measurements and inputs. Good tracking is obtained by the estimated tyre-forces when compared with those simulated by an ADAMS virtual-truck model. A sensitivity analysis determines the susceptibility of the tyre-force estimates to uncertainties in the truck’s parameters.