Who is safe and who is at risk: a study of 20-year-record on accident total loss in different flags

The study examines 20-years of data on 36 world principal fleets and on worldfleets in general, analyses their developments, and particularly their safety records in terms of accidental total loss rates. This study confirms that the open-registry ships tend toward substandard ships. However, some open-registry countries' safety records are quite acceptable. It finds that the safety record of developing maritime countries as a group is better than that of developed maritime countries, of which some are worse than the world average.     

Modeling urban taxi services in road networks: Progress,problem and prospect

Traditionally, many economists have examined the models and economics of urban taxi services under various types of regulation such as entry restriction and price control in an aggregate way. Only recently have we modeled urban taxi services in a network context. A realistic method has been proposed to describe vacant and occupied taxi movements in a road network and taxi drivers' search behavior for customers. A few extensions have been made to deal with demand elasticity and congestion effects together with development of efficient solution algorithms. Calibration and validation of the network taxi service models have been conducted towards their practical applications. This paper presents an overview of the research that has been carried out by the authors to develop network equilibrium models and solution algorithms for urban taxi services, and offers perspectives for future researches.     

Second-order hydrodynamic effects on an arrangement of two concentric truncated vertical cylinders

The second-order diffraction problem by a piston-like arrangement that consists of two concentric surface piercing cylinders is considered. The developed matched axisymmetric eigenfunction expansion solution methodology in cylindrical co-ordinates is based on the semi-analytical formulation of the velocity potentials in the various fluid regions which are defined by the geometry of the two-body arrangement. The main difficulty associated with the specific configuration originates from the fact that the geometry defines two fluid regions that extend up to the free surface in which the inhomogeneous second-order free surface boundary condition has to be fulfilled. To this end the associated velocity potentials in these regions are decomposed into a number of components defining the so-called ‘free’ and ‘locked’ waves. The latter are calculated by solving the resulting Sturm–Liouville problems. The seek second-order velocity potential in the whole fluid domain is then derived by enforcing matching conditions for the radial velocities and the fluid pressures at the cylindrical boundaries of adjacent fluid domains. Numerical results concerning the second-order hydrodynamic loading and the wave run-up on the cylinders are given, whereas special attention is given at incident wave frequency regions where the first-order exciting wave forces attain maximum values due to the resonant fluid motions in the moonpool.     

The changes of activity-travel participation across gender,life-cycle,and generations in Sweden over 30 years

Transportation - This study utilised the Swedish national travel survey covering a period of over 30 years. We investigated the long-term trends in activity-travel patterns of individuals...     

Identification and quantification of plankton bloom events in the Baltic Sea by continuous pCO2 and chlorophyll a measurements on a cargo ship

Continuous measurements of the surface water CO₂ partial pressure (pCO₂) and the chlorophyll a fluorescence were performed in the Baltic Sea using a fully automated measurement system deployed on a cargo ship. The ship commuted regularly at two day intervals between the Mecklenburg Bight (Luebeck) and the Gulf of Finland (Helsinki). The pCO₂ data collected during June 2003 and September 2004 were used to identify biological production events such as the spring bloom and the midsummer cyanobacteria bloom in five different sub-regions. To quantify the net biomass production, the decrease of the total CO₂, ^NC_T (normalized to a uniform alkalinity), during the production periods was calculated using the pCO₂, temperature and salinity records and the mean alkalinity. Taking into account the CO₂ air/sea exchange and the formation of dissolved organic carbon, a simple mass balance yielded the net production of particulate organic carbon which represents the total biomass. The chlorophyll a concentrations obtained from the fluorescence data showed peaks that in most cases coincided with the production maxima and thus supported the interpretation of the pCO₂ data. The production during both the spring bloom (2004) and the midsummer nitrogen fixation period (2003) increased by a factor of about three from the southwest to the northeast. For the spring bloom our estimates were significantly higher than those based on the winter nutrient supply and Redfield C / N and C / P ratios. This indicated the existence of additional nutrient sources such as dissolved organic nitrogen, early nitrogen fixation and preferential P mineralization. Midsummer ^NC_T minima were observed only in 2003 and used to quantify the nitrogen fixation activity and to characterize its interannual variability.     

Adaptive traffic control system: Control strategy,prediction, resolution,and accuracy

Recent advances in traffic control methods have led to flexible control strategies for use in an adaptive traffic control system (ATCS). ATCS aims at controlling the imminent traffic, which is yet to arrive and hence not known perfectly. Therefore, volume prediction is an essential part. Associated with the prediction are two aspects: resolution and accuracy. Recent studies indicate a tradeoff between prediction resolution and accuracy: finer resolutions, larger errors. It is imperative to study the relationship and tradeoff between the control strategy, prediction resolution, and its associated error, which are crucial to the development of ATCS. This study investigates this relationship through an extensive simulation of scenarios in Hong Kong with a recently developed dynamic traffic control model, DISCO. Based on the Hong Kong scenarios conducted with DISCO, the major findings include: (i) the importance of resolution outweighs that of error; (ii) dynamic timing plans generally outperform time‐invariant timing plans; (iii) up to a certain extent, overestimated predictions lead to better results than underestimated predictions.     

Evaluation of automotive forward collision warning and collision avoidance algorithms

Collision warning/collision avoidance (CW/CA) systems target a major crash type and their development is a major thrust of the Intelligent Vehicle Initiative. They are a natural extension of adaptive cruise control systems already available on many car models. Many CW/CA algorithms have recently been proposed but the existing literature mainly focuses on algorithm development. Evaluations of these algorithms have been usually based on subjective ratings. The main contribution of this paper is the utilization of a naturalistic driving data set for the evaluation of CW/CA algorithms. We first collect manual driving data from the ICCFOT project, then process the data by Kalman smoothing, and finally identify 'threatening' and 'safe' data sets according to vehicle brake inputs and vehicle range behavior. Five CW/CA algorithms published in the literature are evaluated against the identified data sets. The performance of these algorithms is determined through a performance metric commonly used in signal detection and information retrieval under unbalanced data population.     

Liner alliances in the globalization era: a strategic tool for Asian container carriers

There has been an increased interest recently in alliances as successors of the large consortia that used to operate in the context of the conference system. Today, having become a common means and term of co-operation in a variety of other industries, alliances are posited as the response of the supply side of liner shipping to important changes on the demand side; alliances have, thus, become predominant in the most important routes for container cargoes. In recent years, however, the list of major container traffic generators and the list of major carriers of containerized cargoes have begun to contain more common entries, generally originating from the Asian region. Asia is, however, a large continent and the entrance of Asian carriers into liner shipping has not been simultaneous; the position, strategies and co-operation strategies of Asian companies have more differences than they share common features. Nevertheless, this paper suggests that alliances are a distinct form of co-operation in liner shipping and the empirical evidence based on a survey in the region supports this hypothesis. The similarity of attitudes of the major Asian container carriers vis a vis alliances is in this way revealing in terms of the range of motivations for participating in the alliance system in a globalized transport environment.     

Association of reduced visibility with crash outcomes

Most of the information necessary for driving a vehicle is regarded as visual information. In spite of its importance, visibility conditions at the time of a crash are often not documented at a high level of detail. Past studies have not examined the quantified values of visibility and its association with crashes. The current study merged data collected from the National Oceanic and Atmospheric Administration (NOAA) with 2010–2012 Florida crash data. From the thousands of logged weather events compiled by the NOAA, the researchers isolated periods of normal visibility and comparable periods of reduced visibility in a matched-pairs study. The NOAA data provided real visibility score based on the spatiotemporal data of the crashes. Additionally, the crash data, obtained from Roadway Information Database (RID), contains several geometric and traffic variables that allow for effects of factors and visibility. The study aims to associate crash occurrence under different levels of visibility with factors included in the crash database by developing ordinal logistic regression. The intent is to observe how different visibility conditions contribute to a crash occurrence. The findings indicate that the likelihood of a crash increase during periods of low visibility, despite the tendency for less traffic and for lower speeds to prevail during these times. The findings of this study will add valuable knowledge to the realm of the impact of visibility in the way of using and designing appropriate countermeasures.     

A Nonlinear Analysis of the Generic Types of Loss of Stability of the Steady State Motion of a Tractor-Semitrailer*

All different types of loss of stability which occur generically for a tractor semitrailer vehicle are studied when varying two parameters namely the speed V of the vehicle and the position d of the center of mass of the trailer. For a fixed value of d and varying V it turns out that only two cases either a divergence or a Hopf bifurcation can occur typically. By means of a nonlinear analysis the post-bifurcation behavior for both cases is treated showing that it is critical in both cases. This latter result means that the system is an imperfection sensitive one for which the calculation only of the linear stability limit, does not have very much practical meaning, because small perturbations of the system (changes of parameters) can lead to a drastic reduction of the critical speed. Our paper furthermore indicates how a nonlinear investigation of stability problems in vehicle dynamics with no restriction to the number of degrees of freedom of the system can be done in a straight forward manner.