Electro-hydraulic braking system for autonomous vehicles

Reducing the number of traffic accidents is a declared target of most governments. Since dependence on driver reaction is the main cause of road accidents, it would be advisable to replace the human factor in some driving-related tasks with automated solutions. To automate a vehicle, it is necessary to control the actuators of a car, i.e., the steering wheel, accelerator, and brake. This paper presents the design and implementation of an electro-hydraulic braking system consisting of a pump and various valves, allowing the control computer to stop the car. It is assembled in conjunction with the original circuit for the sake of robustness and to permit the two systems to halt the car independently. This system was developed for installation in a commercial Citroën C3 Pluriel of the AUTOPIA program. Various tests were carried out to verify its correct operation, and an experiment showing the integration of the system into the longitudinal control of the car is described.     

Optimal design and benefits of a short turning strategy for a bus corridor

We develop a short turning model using demand information from station to station within a single bus line-single period setting, aimed at increasing the service frequency on the more loaded sections to deal with spatial concentration of demand considering both operators’ and users’ costs. We find analytical expressions for optimal values of the design variables, namely frequencies (inside and outside the short cycle), capacity of vehicles and the position of the short turn limit stations. These expressions are used to analyze the influence of different parameters in the final solution. The design variables and the corresponding cost components for operators and users (waiting and in-vehicle times) are compared against an optimized normal operation scheme (single frequency). Applications on actual transit corridors exhibiting different demand profiles are conducted, calculating the optimal values for the design variables and the resulting benefits for each case. Results show the typical demand configurations that are better served using a short turn strategy.     

The <Emphasis Type="Italic">Santiago Panel</Emphasis>: measuring the effects of implementing Transantiago

Although panels offer significant advantages over cross sectional data especially in terms of evaluating the effects of significant policy changes, there are precious few examples of panels built around an important change to an urban transport system. For this reason we took the opportunity of the introduction of Transantiago, a radically new public transport system for Santiago de Chile in February 2007, to form a panel, the first wave of which was taken in December 2006. The final objective was to use this Santiago Panel to estimate mode choice models considering both inertia and policy effects. This document describes both the design and construction of the panel, and presents some results based on an analysis of its four waves; for example, we registered a high percentage of mode change (55.1%) attributable to the introduction of the new system. The panel can claim the highest response rate (or lowest attrition) reported in the literature (95% in the second wave, 92% in the third one, and 85% in the forth one). This hints at the possibility of developing sophisticated models to evaluate the effects of a system shock in the presence of inertia in decision making.     

Perceptions of Threats Facing Cabo de Palos - Islas Hormigas MPA and Potential Solutions

Many marine protected areas (MPAs) face a multitude of threats to the ecosystems that they have been established to conserve. This study is based on 111 interviews conducted in 2013–2014 designed to discover the perceptions of stakeholders about the threats, the causes of the threats, and their responses to the threats, to a well-established MPA – Cabo de Palos - Islas Hormigas (CPH-MPA). This MPA was created to safeguard fisheries and the associated artisanal fishers, but over time it has become a tourism “hotspot.” Resilience theory, which incorporates ecological resilience, social resilience, and individual resilience, helps us to analyze stakeholders' responses to threats by categorizing them into passive, adaptive, and transformative responses. We found respondents identified four main threats – over-fishing, excessive scuba diving, pollution, and invasive species; attributed the threats to three main causes – ineffective management, poor environmental stewardship, and climate change; and expressed three kinds of responses – do nothing, adapt, or transform – with a preference for adaptation and (especially) transformation. The lesson of this study is that it shows how, unless drastic action is taken to curb recreational diving activities, the CPH-MPA is in danger of changing from a fishing reserve to a largely unregulated leisure diving venue, which is unlikely to fulfill the requirements of resilience; ecological, social, or individual.     

A literature review of flexible development of airport terminals

The Master Plan has long been the traditional go-to approach to airport development. It was originally conceived for a scenario of stable growth. In recent decades, however, the airport industry has undergone substantial structural changes, with the traditional Master Plan progressively revealing limitations with regard to airports coping with the market’s unpredictability. There have since been increased calls for flexibility in the approach as an alternative or as a complement to the traditional Master Plan. A flexible development plan helps to accommodate changes within terminals. This paper presents a review of the current literature on airport terminal flexibility, covering a total of 19 reference works. The works were analysed in terms of the concepts, definitions and deployment frameworks, or similar. The review reveals that research in airport terminal flexibility is still in its early stages. A consensual definition has yet to be defined and no robust framework for deploying flexibility has been defined. We propose a new definition of flexible development. Furthermore, flexibility has been studied essentially in the context of expansion. However, in certain regions where land availability is scarce, other forms of airport development may be more important. We conclude the paper with suggestions for future research areas.     

Optimizing bus-size and headway in transit networks

Optimization models for calculating the best size for passenger carrying vehicles in urban areas were popular during the 1980s. These studies were abandoned in the ‘90s concluding that it was more efficient to use smaller buses at higher frequencies. This article returns to this controversial question, starting from the point of view that any calculation of bus size can only be made after considering the demand for each of the routes on the system. Therefore, an optimization model for sizing the buses and setting frequencies on each route in the system is proposed in accordance with the premises detailed below. The proposed model is a bi-level optimization model with constraints on bus capacity. The model allows buses of different sizes to be assigned to public transport routes optimizing the headways on each route in accordance with observed levels of demand. At the upper level the model considers the optimization of the system’s social and operating costs, these are understood to be the sum of the user’s and operator’s costs. At the lower level there is an assignment model for public transport with constraints on vehicle capacity which balances the flows for bus sizes and headways at each iteration. By graphically representing the results of the model applied to a real case, a series of useful conclusions are reached for the management and planning of a fleet of public transport vehicles.     

Participation and desire: leisure activities among Canadian adults with disabilities

As a signatory of the Convention on the Rights of Persons with Disabilities, Canada has assumed the obligation to foster the fundamental right of individuals with impairments to participate in all normal activities and relationships of society. Currently, however, relatively little is known about the extent to which Canadians with disabilities are able to exercise of this right. Previous research has investigated the employment status and commute distance of persons with disabilities in Canada. In this paper, we use the 2006 Participation and Activity Limitation Survey to investigate, from the perspective of Canadian adults with disabilities, the factors that influence (1) their frequency of participation in various leisure and recreation activities; (2) the role of transportation in activity participation; and (3) the desire for more leisure and recreation activities during spare time. The latter question is closely associated to the experience of exclusion. The results of the analysis indicate that some of the very factors that tend to reduce participation also relate to a desire for more leisure and recreation activities.     

Nonlinear gating control for urban road traffic network using the network fundamental diagram

This work proposes a nonlinear model predictive controller for the urban gating problem. The system model is formalized based on a research on existing models of the network fundamental diagram and the perimeter control systems. For the existing models, modifications are suggested: additional state variables are allocated to describe the queue dynamics at the network gates. Using the extended model, a nonlinear model predictive controller is designed offering a ‘non‐greedy’ policy compared with previous, ‘greedy’ gating control designs. The greedy and non‐greedy nonlinear model predictive control (NMPC) controllers are compared with a greedy linear feedback proportional‐integral‐derivative (PID) controller in different traffic situations. The proposed non‐greedy NMPC controller outperforms the other two approaches in terms of travel distance performance and queue lengths. The performance results justify the consideration of queue lengths in dynamic modeling, and the use of NMPC approach for controller design. Copyright © 2014 John Wiley & Sons, Ltd.     

Assessing the influence of indicators’ complexity on hybrid discrete choice model estimates

Transportation - Hybrid discrete choice (HDC) modeling requires indicators to allow for the identification of latent variables. An indicator usually expresses the level of agreement of a respondent...     

Sustainability at Spanish ports specialized in liquid bulk: evolution in times of crisis (2010–2015)

In Spain, 28 Port Authorities of general interest moved more than 168 thousand tonnes of liquid bulk (34% of overall traffic) in 2015. Almost 82% of this amount corresponded to eight ports (G-8) that have a refinery within their facilities. This unique degree of specialization and concentration makes this set of ports an ideal sample to analyse the evolution of their sustainability levels, particularly during the crisis started in 2008 and onwards. A proprietary methodology based on Multidimensional Synthetic Indices has been used. The comparison of the findings obtained for 2010 and 2015 allows a diagnosis of the evolution of port sustainability measured through the economic, institutional, environmental and social dimensions to be established, as well as a study of the patterns of behaviour that each port has followed in this issue.