8,659 research outputs found
Modelling travellers’ risky choice behaviour in revealed preference contexts: A comparison of EUT and non-EUT approaches
Recent work on risky choice modelling has sought to address the theoretical shortcomings of expected utility theory (EUT) by using non-expected utility theoretic (non-EUT) approaches. To date, however, there is little evidence to show whether the complexity of non-EUT actually leads to better model performance. Moreover, almost all the relevant research has adopted stated choice data which, although flexible and cheap, has limited validity. This thesis empirically investigates the feasibility and validity of non-EUT approaches in revealed preference (RP) contexts, in which travel time distribution is extracted from historical travel time data to subsequently present systematic comparisons between EUT and non-EUT approaches. Additionally, this thesis also discusses implementations based on these empirical results and, in particular, highlights the influence of non-EUT on the valuation of travel time savings.
A risky choice framework is proposed so as to incorporate non-EUT into a Random Utility Maximization structure. The non-EUT approaches modelled in the thesis consist of Subjective Expected Value Theory, Subjective Expected Utility Theory, Weighted Utility theory, Rank Dependent Expected Value, Rank Dependent Expected Utility, Prospect Theory, and Cumulative Prospect Theory. The first dataset is collected from the SR91 corridor in California and involves a choice between a free flowing and reliable tolled facility and a congested and unreliable un-tolled facility. The second case study is based on the London Underground (LU) system and involves the choice between alternative competitive underground services linking pairs of stations.
This thesis provides insights into how EUT and non-EUT models perform in the real world. The RP methodology and risky choice framework offers an avenue for future research to identify a wider range of alternative choice theories using realistic data. The empirical results suggest that there are merits in applying non-EUT to the modelling of travellers’ risky choice behaviours.Open Acces
A particle model reproducing the effect of a conflicting flight information on the honeybee swarm guidance
The honeybee swarming process is steered by few scout individuals, which are the unique informed on the location of the target destination. Theoretical and experimental results suggest that bee coordinated flight arises from visual signals. However, how the information is passed within the population is still debated. Moreover, it has been observed that honeybees are highly sensitive to conflicting directional information. In fact, swarms exposed to fast-moving bees headed in the wrong direction show clear signs of disrupted guidance. In this respect, we here present a discrete mathematical model to investigate different hypotheses on the behaviour both of informed and uninformed bees. In this perspective, numerical realizations, specifically designed to mimic selected experiments, reveal that only one combination of the considered assumptions is able to reproduce the empirical outcomes, resulting thereby the most reliable mechanism underlying the swarm dynamics according
to the proposed approach. Specifically, this study suggests that (i) leaders indicate the right flight direction by repeatedly streaking at high speed pointing towards the target and then slowly coming back to the trailing edge of the bee cloud; and (ii) uninformed bees, in turn, gather the route information by adapting their movement to all the bees sufficiently close to their position
Plataforma de informação de tráfego para redução de consumos e emissões
Doutoramento em Engenharia MecânicaApesar das recentes inovações tecnológicas, o setor dos transportes
continua a exercer impactes significativos sobre a economia e o ambiente.
Com efeito, o sucesso na redução das emissões neste setor tem sido inferior
ao desejável. Isto deve-se a diferentes fatores como a dispersão urbana e a
existência de diversos obstáculos à penetração no mercado de tecnologias
mais limpas. Consequentemente, a estratégia “Europa 2020” evidencia a
necessidade de melhorar a eficiência no uso das atuais infraestruturas
rodoviárias. Neste contexto, surge como principal objetivo deste trabalho, a
melhoria da compreensão de como uma escolha de rota adequada pode
contribuir para a redução de emissões sob diferentes circunstâncias espaciais
e temporais. Simultaneamente, pretende-se avaliar diferentes estratégias de
gestão de tráfego, nomeadamente o seu potencial ao nível do desempenho e
da eficiência energética e ambiental. A integração de métodos empíricos e
analíticos para avaliação do impacto de diferentes estratégias de otimização
de tráfego nas emissões de CO2 e de poluentes locais constitui uma das
principais contribuições deste trabalho.
Esta tese divide-se em duas componentes principais. A primeira,
predominantemente empírica, baseou-se na utilização de veículos equipados
com um dispositivo GPS data logger para recolha de dados de dinâmica de
circulação necessários ao cálculo de emissões. Foram percorridos
aproximadamente 13200 km em várias rotas com escalas e características
distintas: área urbana (Aveiro), área metropolitana (Hampton Roads, VA) e um
corredor interurbano (Porto-Aveiro). A segunda parte, predominantemente
analítica, baseou-se na aplicação de uma plataforma integrada de simulação
de tráfego e emissões. Com base nesta plataforma, foram desenvolvidas
funções de desempenho associadas a vários segmentos das redes estudadas,
que por sua vez foram aplicadas em modelos de alocação de tráfego.
Os resultados de ambas as perspetivas demonstraram que o consumo de
combustível e emissões podem ser significativamente minimizados através de
escolhas apropriadas de rota e sistemas avançados de gestão de tráfego.
Empiricamente demonstrou-se que a seleção de uma rota adequada pode
contribuir para uma redução significativa de emissões. Foram identificadas
reduções potenciais de emissões de CO2 até 25% e de poluentes locais até
60%. Através da aplicação de modelos de tráfego demonstrou-se que é
possível reduzir significativamente os custos ambientais relacionados com o
tráfego (até 30%), através da alteração da distribuição dos fluxos ao longo de
um corredor com quatro rotas alternativas.
Contudo, apesar dos resultados positivos relativamente ao potencial para a
redução de emissões com base em seleções de rotas adequadas, foram
identificadas algumas situações de compromisso e/ou condicionantes que
devem ser consideradas em futuros sistemas de eco navegação. Entre essas
condicionantes importa salientar que: i) a minimização de diferentes poluentes
pode implicar diferentes estratégias de navegação, ii) a minimização da
emissão de poluentes, frequentemente envolve a escolha de rotas urbanas
(em áreas densamente povoadas), iii) para níveis mais elevados de
penetração de dispositivos de eco-navegação, os impactos ambientais em
todo o sistema podem ser maiores do que se os condutores fossem orientados
por dispositivos tradicionais focados na minimização do tempo de viagem.
Com este trabalho demonstrou-se que as estratégias de gestão de tráfego
com o intuito da minimização das emissões de CO2 são compatíveis com a
minimização do tempo de viagem. Por outro lado, a minimização de poluentes
locais pode levar a um aumento considerável do tempo de viagem. No
entanto, dada a tendência de redução nos fatores de emissão dos poluentes
locais, é expectável que estes objetivos contraditórios tendam a ser
minimizados a médio prazo. Afigura-se um elevado potencial de aplicação da
metodologia desenvolvida, seja através da utilização de dispositivos móveis,
sistemas de comunicação entre infraestruturas e veículos e outros sistemas
avançados de gestão de tráfego.Despite recent technological innovations, transportation sector is still producing
significant impacts on the economy and environment. In fact, the success in
reducing transportation emissions has been lower than desirable due to several
factors such as the urban sprawl and several barriers to the market penetration
of cleaner technologies. Therefore, the “Europe 2020” strategy has emphasised
the relevance of improving the efficiency in the transportation networks through
the better use of the existing infrastructures. In this context, the main objective
of this thesis is increasing the understanding of how proper route choices can
contribute to reduce emissions output over different spatial and temporal
contexts. Simultaneously, it is intended to evaluate the potential of different
traffic management strategies in terms of traffic performance and
energy/environmental efficiency. The integration of empirical and analytical
methods to assess the impact of different traffic optimization strategies on CO2
emissions and local pollutants constitutes one the main contributions of this
work.
This thesis has been divided in two main parts. The first is predominantly
empirical, using field data as the main source of information. Using GPS
equipped vehicles, empirical data for approximately 13200 km of road coverage
have been collected to estimate energy and emissions impacts of route choice
in three different scenarios: a medium-sized urban area (Aveiro), a metropolitan
area (Hampton Roads, VA) and an intercity corridor (Oporto-suburban area).
The second part, predominantly analytical, is essentially based on the output of
traffic simulators and optimization models. The analytical component was
based on the capability of microscopic traffic models to generate detailed
emissions information and to generate link-based performance functions. Then,
different traffic management strategies were tested to evaluate road networks
in terms of traffic performance and emissions.
Both outcomes of the empirical and analytical approaches have
demonstrated that fuel use and emissions impacts can also be significantly
reduced through appropriate route choices and advanced traffic management
systems. The empirical assessment of route choice impacts has shown that
both during off peak and peak periods, the selection of an appropriate route
can lead to significant emissions reduction. Depending on the location,
potential emissions savings of CO2 up to 25% and local pollutants up to 60%
were found. The analytical approach has demonstrated that it is possible to
significantly reduce system environmental costs (30%) by modifying traffic flow
distribution along a corridor with 4 alternative routes. However, despite the
positive results in terms of the potential for emissions reduction based on
appropriate route choices, a number of important trade-offs that need to be
considered in future implementations of eco-routing systems. Among these
trade-offs it is worth noting that: i) different pollutants may lead to different ecorouting
strategies, ii) the minimization of pollutants emissions often involves
choosing urban routes (densely populated), iii) for higher penetration levels of
eco-routing devices considering local pollutants, system environmental
impacts can be higher than if drivers were guided under the traditional devices
focused on travel time.
With this research, it has been demonstrated that road traffic management
strategies focused on minimizing CO2 emissions and fuel consumption can be
compatible with the minimization of system travel time. On the other hand the
minimization of local pollutants may lead to considerable increases in travel
time. However, given the trend rate of reduction in the emissions factors of
local pollutants, it is expected that such trade-offs would tend to be minimized
in medium term. Thus, the developed methodology has great potential for
further real life application, either through the use of nomadic devices,
infrastructures to vehicle communication or different advanced traffic
management systems
Health impacts of bike sharing system – A case study of Shanghai
Background:
Bike sharing systems have been promoted in many countries. Bike sharing can alleviate urban air pollution and reduce road congestion during peak hours in the morning and evening. In addition, using shared bicycles as a daily commuting tool can help users increase their daily exercise volume. This study evaluates the health effects of shared bicycle use. The evaluation of health is prospective, and we utilize current data to evaluate and analyze the health of future users. The primary health considerations for users include physical activity, PM2.5 levels, and collision rates. Physical exercise might be hindered by high concentrations of PM2.5. Thus, while riding in conditions of very high PM2.5 concentration, the pollutants taken by the traveler will hurt the body and counteract the advantages of physical exercise. This research demonstrates that cycling during periods of low or moderate PM2.5 concentrations should lead to an overall reduction premature mortality. /
Data and methods:
We perform a health assessment study to quantify the health risks and benefits of car trip substitution by bike trip. We collected the cycling data from Mobike shared bicycles operator in Shanghai established in August 2016. From August 1st to August 31st, 2018, there were 1,023,603 orders and 3,036,936 cycling users. During the computational analysis, we examined three factors: physical activity, PM2.5 pollution, and bicycle collision rate, and then summed the results to determine the cyclist's risk of early death. Three scenarios are created to estimate the annual expected number of deaths (increasing or reduced) due to physical activity, road traffic fatalities, and air pollution. /
Results:
Air pollution exposure was assessed using variations in the background fine particulate matter (PM2.5) concentration, which was 45 μg/m3 on average in August 2016 in Shanghai. Cycling under these settings, the advantages of physical exercise exceeded the hazards posed by pollution. When PM2.5 concentrations exceed 45 μg/m3, seven to eight people will avert early mortality for every 306,936 users. It means 23–26 per million cyclists would avoid premature death. When PM2.5 concentrations exceed 68 μg/m3, 1 to 2 people will be significantly harmed by air pollution and 4–7 out of every million cyclists are negatively affected by high PM2.5 concentrations. /
Conclusions:
These results demonstrate that shared cycling can avoid premature mortality. In addition, from the perspective of urban pollution, commuters choosing bicycles instead of cars to travel can reduce urban air pollution, improve air quality, and reduce traffic jams in the morning and evening peaks. Further research on the co-benefits of shared bicycles would be helpful to planners
Theories of understanding others: the need for a new account and the guiding role of the person model theory
What would be an adequate theory of social understanding? In the last decade, the philosophical debate has focused on Theory Theory, Simulation Theory and Interaction Theory as the three possible candidates. In the following, we look carefully at each of these and describe its main advantages and disadvantages. Based on this critical analysis, we formulate the need for a new account of social understanding. We propose the Person Model Theory as an independent new account which has greater explanatory power compared to the existing theorie
Statistical features of edge turbulence in RFX-mod from Gas Puffing Imaging
Plasma density fluctuations in the edge plasma of the RFX-mod device are
measured through the Gas Puffing Imaging Diagnostics. Statistical features of
the signal are quantified in terms of the Probability Distribution Function
(PDF), and computed for several kinds of discharges. The PDFs from discharges
without particular control methods are found to be adequately described by a
Gamma function, consistently with the recent results by Graves et al [J.P.
Graves, et al, Plasma Phys. Control. Fusion 47, L1 (2005)]. On the other hand,
pulses with external methods for plasma control feature modified PDFs. A first
empirical analysis suggests that they may be interpolated through a linear
combination of simple functions. An inspection of the literature shows that
this kind of PDFs is common to other devices as well, and has been suggested to
be due to the simultaneous presence of different mechanisms driving
respectively coherent bursts and gaussian background turbulence. An attempt is
made to relate differences in the PDFs to plasma conditions such as the local
shift of the plasma column. A simple phenomenological model to interpret the
nature of the PDF and assign a meaning to its parameters is also developed.Comment: 27 pages. Published in PPC
Understanding the impact of risk perception in leisure tourism-related decisions and the role of attitudes and preferences
The contemporary tourism industry is often forced to face events that represent a threat to individuals’ safety. Life- threatening events pose a challenge to travelers’ intentions to plan a leisure trip and influence in a substantive manner human decisions. Individual sensitivity towards potential hazards show a great deal of variation among consumers and several tourism scholars have spent the last years investigating the sources of heterogeneity in hazard-induced travel decisions. The present PhD dissertation collects three research articles dealing with tourist risk perception, hazard-induced travel behaviour and the role of individual traits in decision-making influenced by potential hazards. The specific aim of the study is to investigate the relationship between travel attitudes and hazard-induced risk perception, and between risk perception and travel choices. Furthermore, the work intends to assess the differences between distinct life-threatening hazards and the way in which these determine travel decisions. For the purpose of empirical analysis, a structured survey was administered to a sample of university students. Part of the questionnaire was dedicated to a stated preference experiment in which individuals had to choose between hypothetical alternatives of travels characterized by hazards. In this thesis, advanced econometric techniques – namely, Integrated Choice and Latent Variable modelling – are implemented in order to allow unobservable individual traits to be tested as significant determinants of travellers’ decisions. The main results highlight that travel attitudes bear a significant role in shaping risk perception only for certain types of hazards. The analysis of stated preferences data show that an increasing level of risk perception negatively influences the likelihood to travel to dangerous destinations, but important and significant differences are present in the sample of respondents
Reconsidering The Impact of Environment on Long-Run Growth When Pollution Influences Health and Agents Have Finite-Lifetime
Using an overlapping generation model à la Blanchard (1985) with human capital accumulation, this article demonstrates that the influence of environment on optimal growth in the long-run may be explained by the detrimental effect of pollution on life expectancy. It also shows that, in such a case, greener preferences are growth- and welfare-improving even if the ability of the agents to learn is independent to pollution and utility is additively separable. Finally, it establishes that it is possible to implement a win-win environmental policy.Growth, Environment, Overlapping Generations, Human Capital, Health
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