Modelling of Driver/Vehicle Directional Control System

Different driver models and driver/vehicle/road closed-loop directional control systems are reviewed and compared. Evaluation methods of vehicle handling quality based on closed-loop system dynamics, stability of the closed-loop system, and optimization of vehicle design are discussed.     

Risk analysis of vessel traffic systems

A risk analysis approach to the capital planning of vessel traffic services (VTS) is embedded within the benefit-cost methodology. The method is discussed in the Canadian context, but has already been used to plan the Hong Kong VTS system. Recently, in response to the Exxon Valdez oil spill, the US Congress asked for a study of the requirements for VTS systems in American ports and waterways, and the US Coast Guard chose to apply our risk analysis approach to their study.     

Rule-based optimization of midship structures

A rule-based overall design methodology for midship structures of small inland waterways vessels is presented. It is shown how the designer, under conflicting requirements, can select the optimum design by using a combined objective function with priority factors assigned to individual design criteria. The concept of optimization, in large-scale structural design problems, is extended to the local members (the stiffening elements) of the ship structure, so that the stiffeners can be specified by their actual dimensions instead of section moduli. The effects of price-structure (labour rate to material price ratio) and the choice of type of stiffener on design are investigated. Standard sections and optimized fabricated sections are taken as the alternative options for selecting the stiffeners. Conversion of exact mathematical optimum solutions into production-oriented designs is also demonstrated in a series of practical applications of the proposed method.     

Post OPA-90 vessel oil spill differentials: transfers versus vessel accidents

This study investigates vessel oil spill differentials for transfer and vessel-accident spills for the post Oil Pollution Act of 1990 (OPA-90) period. In-water and out-of-water transfer/vessel-accident oil spill equations are estimated, utilizing tobit regression analysis and data of individual vessel oil spills (of oil-cargo and non-oil-cargo vessels) investigated by the US Coast Guard for the 1991-1995 period. In the data, 47.5% (94.1%) of in-water (out-of-water) gallons of oil spilled were transfer spills; non-oil-cargo vessels accounted for 44.2% of all gallons spilled. The estimation results suggest that out-of-water transfer spills are larger in size than vessel-accident spills, but are similar in size for in-water spills. Transfer/vessel-accident spill differentials exist (do not exist) among determinants of in-water (out-of-water) spills. The policy implication of the results is that a vessel oil spill-reduction differentiation regulatory regime is needed that differentiates between transfer and vessel-accident spills and in-water and out-of-water spills for reducing vessel oil spills.     

Patterns of car usage and restraint modelling

Transport demand forecasting procedures have traditionally employed household based modal split models implicitly assuming a selection of mode for each trip based on relative generalised cost. A detailed examination of the trip patterns of a sample of household in West Yorkshire shows that in fact there is little discretionary choice of public transport; public transport trips in car owning households generally being explained in terms of the specific unavailability of the car for such trips. Two versions of a category analysis model for modal split are based on this observation and applied to household data for Glamorgan and Monmouthshire to show that such a procedure is workable and produces results comparing favourably with traditional approaches. The likely implications of three types of restraint policy are examined and it is concluded that the existing interdependence in trip patterns and modal choice within the household is of great significance in determining their effects. In particular it appears that positive attempts to increase vehicle occupancy at the peak are likely to be more favourable to public transport finances than the more negative policies to restrain use of the car for journey to work, or second car ownership.     

Estimating gravity model parameters: A simplified approach based on the odds ratio

Two computationally simple methods for calibrating the gravity model are presented in this paper. The use of each is demonstrated on several origin-destination trip tables, and the results compared with those obtained from the UTP system gravity model calibration procedure. Our methods, based on the odds ratio, perform at least as well as that of UTP system by several standard criteria.     

Network equilibrium for congested multi‐mode networks with elastic demand

This paper proposes an elastic demand network equilibrium model for networks with transit and walking modes. In Hong Kong, the multi‐mode transit system services over 90% of the total journeys and the demand on it is continuously increasing. Transit and walking modes are related to each other as transit passengers have to walk to and from transit stops. In this paper, the multi‐mode elastic‐demand network equilibrium problem is formulated as a variational inequality problem where the combined mode and route choices are modeled in a hierarchical logit structures and the total travel demand for each origin‐destination pair is explicitly given by an elastic demand function. In addition, the capacity constraint for transit vehicles and the effects of bi‐directional flows on walkways are considered in the proposed model. All these congestion effects are taken into account for modeling the travel choices. A solution algorithm is developed to solve the multi‐mode elastic‐demand network equilibrium model. It is based on a Block Gauss‐Seidel decomposition approach coupled with the method of successive averages. A numerical example is used to illustrate the application of the proposed model and solution algorithm.     

An Approach to Determining Worst Case Platoon Behavior

This paper presents a method with which one can evaluate alternative platooning control strategies with respect to worst case behavior. The motivation is to provide platoon control designers with an objective means of evaluating robustness in the face of system uncertainties. The approach can be viewed as an extension of optimal control procedures and is applicable to complex, nonlinear systems. An arbitrary number of uncertain parameters, unmodeled components and inputs are allowed. The end result is a lower bound for the worst case platoon performance.