Modelling reservation-based shared autonomous vehicle services: A dynamic user equilibrium approach

Shared Autonomous Vehicles (SAVs) are expected to be used for regular and pre-planned trips. Such trips are suitable for reservation-based services, wherein the customer needs to book for a trip in advance. Systems enabling reservation of trips can allow for better planning of routes and schedules, and if optimally designed, enable higher efficiency. The primary objective of this research is to model the effects of such a system, by formulating and solving the combined Dynamic User Equilibrium and Shared autonomous vehicle Chain Formation (DUESCF) problem. The problem is formulated as a bilevel model based on game theory, involving road users and SAV service operator. Given a situation where conventional private and shared autonomous vehicles co-exist, road users select paths and departure times to maximize a perceived utility (commonly treated as minimizing a disutility) by forming a DUE (fixed point problem), and the SAV service operator tries to maximize the performance by forming appropriate SAV chains (combinatorial problem). The final objective of this bilevel model is a traffic assignment that includes SAV chain formation, such that both road users and SAV service operator obtain optimal solutions by reaching a Nash equilibrium, where no player is better off by unilaterally changing their decisions. A solution approach, based on Iterative Optimization and Assignment (IOA) method, is proposed with path flow and SAV performance changes as convergence criteria. Furthermore, the solution approach is tested for its robustness, and a scenario analysis is carried out to evaluate the impacts of reservation-based SAV services. The results show that a ridesharing SAV system is better compared to a carsharing and a mixed system consisting of both, in terms of total system travel time, congestion levels, total vehicle kilometres travelled and vehicle requirements

Social media and travel behaviour

Social media has emerged as a trend that greatly influences transportation and travel behaviour. This influence is identified both on the way that travellers make decisions concerning transportation related matters and the fact that social media allow tracing back the way that these decisions were made and allow for the collection of data, related to understanding these decisions. This chapter introduces these interdependences between Social Media (SM) and travel behaviour by presenting a collection of use cases and methods. Firstly, an introduction to the existing dominant SM is presented, including current availability of data and a discussion of helpful frameworks that could facilitate transportation related research on the subject. The pertinent literature on the User Generated Content (UGC) generation process and users’ personality characteristics is reviewed, in order to gain understanding on the characteristics of the users, who generate the content. Secondly, the relation of SM to travel behaviour is established by investigating the impact of UGC to the transportation system and vice versa. The capabilities of SM to allow for behavioural interventions is discussed towards the direction of inducing more socially responsible behaviour. Finally, related case studies are presented

Exploring the Effects of University Campus Decentralization to Students’ Mode Choice

Mobility patterns and travel behavior aspects of students traveling to universities, are gaining attention, as the completion of such every day trips are rather complicated. University students form a social group, essentially autonomous in terms of mode choice decision making. Understanding the mode choice decision process, may reveal the most appropriate interventions for achieving sustainable transport goals. The current study aims to examine various aspects of university students’ travel bahaviour such as travel distance, travel time, comfort and safety in the city of Xanthi, Greece. Moving a step forward, the paper provides a better understanding of students’ travel patterns in two different environments due to the University relocation from an urban environment to a more isolated one. For this purpose, a questionnaire survey is conducted where students describe their travel habits before and after the relocation. In addition, students are given a choice set comprised of eight different factors hypothesized to internalize the effect of the relocation on mode choice for the trips to and from the University and they are asked to prioritize them ranking them from the most significant one to the least important. For the analysis two Multinomial Logit models are developed. The results verify initial considerations; distance and time are the most important factors for both cases while the use of public transport instead of walking increases the importance of economy and safety

Ignition and burn control characteristics of thermonuclear plasmas

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1990.Includes bibliographical references (leaves 232-238).by Emmanouil Antony Chaniotakis.Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1990

Stochastic user equilibrium traffic assignment with equilibrated parking search routes

In this paper we define and formulate the concept of parking search routes (PSR) where a driver visits a sequence of parking locations until the first vacant parking spot is found and in doing so may account for (expected) parking probabilities. From there we define and formulate the stochastic user equilibrium (SUE) traffic assignment in which no driver, by unilaterally changing its PSR, can lower its perceived expected generalized costs. Recognizing the interdependency between PSR flows, travel times and parking probabilities, we propose a queuing model in order to compute endogenous parking probabilities accounting for these factors as well as maximum admissible search times. To solve the SUE assignment with equilibrated PSR we propose a solution algorithm, including a method for PSR choice set generation. The model is implemented and applied both to a number of experimental cases to verify its properties and to a real-life setting to illustrate its usefulness in parking-related studies.Transport and Plannin

Mapping Social Media for Transportation Studies

Social media has dominated the online lives of individuals and has created a research stream with potential applications in many scientific fields, including transportation. This article attempts to map the landscape of social media, focusing on transportation, by identifying the main streams of research in the pertinent literature and analyzing the taxonomy of the dominant social media in terms of functionalities fulfilled and data availability. Additionally, the authors present a strengths, weaknesses, opportunities, and threats (SWOT) analysis and examine the applicability of data collected from social media sources in a case study

Characterizing the adoption and frequency of use of a pooled rides service

Pooled-ride services have a significant potential for reducing traffic externalities and enhancing transportation systems in the urban environment. These services and their users’ characteristics still need further inspection and exploration. We investigated factors encouraging the shift from the currently used modes to pooled-ride-services, the choice between different pooled services vehicles types, and the frequency of use of pooled-rides, using data collected via a large-scale online survey conducted in Mexico City, Mexico (CDMX) for a start-up that organizes pooled rides, Jetty. We modeled the pooled-ride-service adoption process as a function of the users’ sociodemographics, latent travel attitudes, accessibility to public transportation, trip characteristics, reasons to use the service, and users’ activities during the trips. We estimated hybrid choice models and binary logit models, which show that users’ sociodemographic and travel attitudes are the main factors impacting the shift from different modes to pooled rides. Service-related characteristics such as multi-tasking, trip fare, and avoiding parking problems also impact the shift decision. On the other hand, the frequency of service use is mainly impacted by trip characteristics such as total trip distance, and the headway at the user’s home location nearest Metro stations. Income, employment status, number of cars in the household, and gender were the only sociodemographic factors impacting the service use frequency directly and indirectly

Bridging the Gap between Large Research Infrastructures in Physics and Society through Citizen Science

Despite the large progress of science in the frontiers of Physics and its impact to our lives, a gap between research and society is observed. In this article we discuss the potential of citizen science to help bridge this gap by both supporting scientific research and increasing society’s science literacy