Simulating ad-hoc demand-responsive transportation: a comparison of three approaches

Transport models are used to evaluate new infrastructure and public transport services, varied levels of demand, and new ideas for demand management. Exploring these proposals virtually is easier than implementation and testing in situ. However, existing models are based around traditional forms of transportation. As part of a feature analysis using a case study approach, three different simulation packages (a simple custom-developed package, traffic microsimulation, and agent-based simulation) are used to develop and demonstrate simulations of demand-responsive transportation (DRT) and analyze the advantages and disadvantages of each simulation approach for evaluating DRT. While the simulations display some relational replication (meaning they produce similar relational patterns with respect to certain variables), they do not show distributional replication (that is, the value of the results is not statistically similar), meaning that under- or over-estimation of predicted travel could occur. Recommendations for the application of each modeling approach are made.     

Assessing a maritime service website prototype in a ship bridge simulator: navigators’ experiences and perceptions of novel e-Navigation solutions

The aim of this study was to assess proof of concept and usability of a maritime service website prototype in a full-mission ship bridge simulator through Swedish mariners’ experiences and perceptions. This test was part of the European Commission’s EfficienSea2 project for e-navigation. The prototype was intended as an aid to existing standard systems and methodologies for planning, executing and monitoring voyages. The study began with 5 days of simulator trials focused on today’s standard practices. This served as a baseline to compare to subsequent 4 days of simulator trials testing the prototype. For data collection, observations, video footage, interviews, and eye tracking were used. Data analysis included breaking apart the qualitative data to capture the perceptions of the participants, and a preliminary analysis of eye-tracking data as a complement. The results suggested that the prototype could be more suitable for a route planning stage, that the participants were familiar with similar existing solutions from other manufacturers, and that the contents of the tool would be most beneficial if integrated within the Electronic Chart Display and Information Systems (ECDIS). There is a pressing need for the novel solutions to be user needs-driven, integrated with the existing technologies, and standardized across the domain, and these processes must go hand-in-hand with accounting for all involved stakeholders, procedures, regulations, and training, as this will alter the course of shipping.     

A model of the travel to work limits of parents

This paper considers the length of time that parents are willing to travel to an existing or new job. Using data for over 12,000 parents it finds that many characteristics were associated with being less likely to be willing to travel to work for at least an hour (roundtrip). These include: being a women, those out of work, having children under 5, being a lone parent and using formal childcare. Professionals and associate professions were more willing to travel for longer periods. In terms of location, those in accessible small towns and rural areas were willing to travel more than those in larger urban areas and those in remote rural areas willing to travel most. Policy implications are also set out.     

Converting mixed pedestrian flows into equivalent commuters using standard pedestrian equivalent factors

This paper develops the concept of standard pedestrian equivalent (SPE) factors for converting a mixed pedestrian flow into an equivalent commuter flow. After a comprehensive review of passenger car equivalent (PCE) methodologies, the equal total travel time method is utilised for SPE estimation. A micro-simulation approach is employed for the formulation of the total travel time–flow relationship. Field data collected on walking speed distributions for commuters and older adults in Australia are used as model inputs. An independent samples t-test confirms the significant difference between walking speeds of commuters and older adults. For this paper, a unidirectional flow on flat walkways is initially considered and evaluated across proportions of older people, different flows and different walkway widths. The introduction of older adults significantly increases total travel time especially under congested conditions. Results of this investigation can be used for evaluation or design of pedestrian facilities experiencing similar flow conditions.     

A velocity and payload dependent emission model for heavy-duty road freight transportation

The paper develops a forecasting model of emissions from traffic flows embracing the dynamics of driving behavior due to variations in payload. To measure of emissions at the level of individual vehicles under varying payloads a portable emission measurement system is used. This paper reports on a model based on data at the level of individual vehicles for a representative road trajectory. The model aggregates the data to the level of a homogeneous flow dependent of velocity and specific power, which is dependent on payload weight. We find a lean specification for the model that provides emission factors for CO₂, NO_x, HC, CO, and NO₂. The results indicate that, in comparison with earlier models, NO_x emissions in particular tend to be underestimated.     

Governance Responses to Rapid Growth in Environmentally Sensitive Areas of Coastal Australia

The twin forces of rising affluence and population are altering coastal communities around the world. High amenity, environmentally sensitive areas—particularly attractive, non-metropolitan coastal environments—are witnessing a tidal wave of in migration from former urbanites. As a result, these communities are struggling to accommodate growing numbers of people with urban tastes and rural dreams in areas with governance structures and physical infrastructure designed for occasional tourists. This article looks at how governance frameworks in coastal Australia respond to the profound environmental, social, and cultural implications of this process. We offer a typology of non-metropolitan coastal growth settings—from exurban contexts to isolated coastal hamlets—and identify the main environmental, social, economic, and governance issues they face. We then outline the policy and legislative framework governing coastal areas in Australia and show how this framework is interpreted at the local level through an analysis of five local plans covering different coastal settings.     

Effect of open skies in the Middle East region

This research aims to estimate potential inter-regional passenger flows for air transport in the Middle East under open skies polices, once deregulation agreements are reached between neighboring countries. To arrive at reasonable demand estimates, Western and Eastern European demand data was analyzed as a first step, since it is assumed that current Middle Eastern demand is distorted as a direct result of regional political instability. The major factors affecting demand, based on the European dataset, included population size, gross domestic product (GDP) per capita, absolute difference in GDP per capita between two countries, great circle distance and membership of the European Union and World Trade Organization. Subsequently, a 21 country database was estimated for passenger flow in the Middle East region on an average peak season day. The demand estimations became input for a hub location model (p-hub median formulation) in order to achieve the second major aim of this research, objective identification of potential regional gateways. The results proved robust to both single and multiple allocation model assumptions, with Cairo and Tehran consistently achieving hub status, along with Istanbul and Riyadh, as the number of potential hubs increased. Finally, this research shows that under conditions of peace, given existing socio-economic indicators, inter-regional passenger demand flow could increase by upwards of 51% and regulatory authorities ought to consider the necessary infrastructure and demand management policies to enable the conservative regional demand growth estimated.     

Model-Predictive Control Strategy for an Array of Wave-Energy Converters

To facilitate the commercialization of wave energy in an array or farm environment, effective control strategies for improving energy extraction efficiency of the system are important. In this paper, we develop and apply model-predictive control (MPC) to a heaving point-absorber array, where the optimization problem is cast into a convex quadratic programming (QP) formulation, which can be efficiently solved by a standard QP solver. We introduced a term for penalizing large slew rates in the cost function to ensure the convexity of this function. Constraints on both range of the states and the input capacity can be accommodated. The convex formulation reduces the computational hurdles imposed on conventional nonlinear MPC. For illustration of the control principles, a point-absorber approximation is adopted to simplify the representation of the hydrodynamic coefficients among the array by exploiting the small devices to wavelength assumption. The energy-capturing capabilities of a two-cylinder array in regular and irregular waves are investigated. The performance of the MPC for this two-WEC array is compared to that for a single WEC, and the behavior of the individual devices in head or beam wave configuration is explained. Also shown is the reactive power required by the power takeoff system to achieve the performance.

     

Residual stress distributions in ship hull specimens

This paper provides an in-depth study of residual stress distributions found in stiffened steel plate structures, such as those typically used in ship hulls. The effect of stiffener spacing on the distribution of residual stress components was studied. The welding heat input was also varied between high and moderate to study the effect of heat input level on residual stress distributions. Four specimens, resembling typical stiffened steel plate structures used in ship hulls were built and tested. Steel plates of 9.5 mm thickness were stiffened by welding L127 × 76 × 9.5 steel angles. The test was completed using the neutron diffraction method. The three normal components of residual stress were obtained in this study. It was found that a lower heat input results in higher tensile residual stress and that there exists a critical stiffener spacing somewhere beyond 250 mm that creates a maximum tensile residual stress value near the welded connection.     

Commuting times – The role of gender,children and part-time work

It has been widely established in the UK and other developed countries that men commute longer than women and that fathers travel furthest to work while mothers travel least. This paper models a wide variety of factors that affect commuting times including gender, presence of children and working hours (part- and full-time work). It finds that of particular importance to the length of commute are the worker’s age, having children, the age of their youngest child, occupation, weekly pay, and mode of transport (with public transport being associated with longer commutes). The region of residence was important for men and women working full-time but not for part timers (except for women in London), while ethnicity and owner occupation were associated with commuting length for full-time men only. The results suggest that while gender, working hours and childcare responsibility are often inter-related, it is useful to disaggregate their effects when modelling or developing policy.