Optimizing Coordinated Vehicle Platooning: An Analytical Approach Based on Stochastic Dynamic Programming

Platooning connected and autonomous vehicles (CAVs) can improve traffic and fuel efficiency. However, scalable platooning operations require junction-level coordination, which has not been well studied. In this paper, we study the coordination of vehicle platooning at highway junctions. We consider a setting where CAVs randomly arrive at a highway junction according to a general renewal process. When a CAV approaches the junction, a system operator determines whether the CAV will merge into the platoon ahead according to the positions and speeds of the CAV and the platoon. We formulate a Markov decision process to minimize the discounted cumulative travel cost, i.e. fuel consumption plus travel delay, over an infinite time horizon. We show that the optimal policy is threshold-based: the CAV will merge with the platoon if and only if the difference between the CAV's and the platoon's predicted times of arrival at the junction is less than a constant threshold. We also propose two ready-to-implement algorithms to derive the optimal policy. Comparison with the classical value iteration algorithm implies that our approach explicitly incorporating the characteristics of the optimal policy is significantly more efficient in terms of computation. Importantly, we show that the optimal policy under Poisson arrivals can be obtained by solving a system of integral equations. We also validate our results in simulation with Real-time Strategy (RTS) using real traffic data. The simulation results indicate that the proposed method yields better performance compared with the conventional method

The application of chaos theory to forecast urban traffic conditions

PhD ThesisThis thesis explores the application of Chaos Theory to forecast urban traffic conditions. The research takes advantage of a highly resolved temporal and spatial data available from the Split Cycle Optimisation Technique (SCOOT) system, in order to overcome the limitations of previous studies to investigate applying Chaos Theory in traffic management. This thesis reports on the development of a chaos-based algorithm and presents results from its application to a SCOOT controlled region in the city of Leicester, UK. A Phase Space Reconstruction method is used to analyse non-linear data from the SCOOT system, and establishes that a 20 second resolved data is suitable for understanding the dynamics of the traffic system. The research develops the Lyapunov exponent as a chaos-based parameter to forecast link occupancy using a multiple regression model based on the temporal and spatial relationships across the links in the network. The model generates a unique forecast function for each link for every hour of the day. The study demonstrates that Lyapunov exponents can be used to predict the occupancy profile of links in the network to a reasonably high level of accuracy (R-values generally greater than 0.6). Evidence also suggests that the predictions from the Lyapunov exponents (rather than occupancy) make it possible to report on the impending conditions over a wider part of the network so that imminent congested conditions can be foreseen in advance and mitigation measures implemented. Thus, the thesis concludes that incorporating chaos-based algorithms in this way can enable urban traffic control systems to be one-step ahead of traffic congestion, rather than one-step behind. This would improve the management of traffic on a more strategic level rather than purely within smaller network regions thus playing an important role in improving journey times and air quality and making a vital contribution to mitigating climate change

The r-evolution of driving: from Connected Vehicles to Coordinated Automated Road Transport (C-ART)

Connected and automated vehicles could revolutionise road transport. New traffic management approaches may become necessary, especially in light of a potential increase in travel demand. Coordinated Automated Road Transport (C-ART) is presented as a novel approach that stakeholders may consider for an eventual full realisation of a safe and efficient mobility system.JRC.C.4-Sustainable Transpor

Queue methods for variability in congested traffic

Time-dependent queue methods are extended to calculate variances of stochastic queues along with their means, and thereby provide a tool for evaluation and better understanding of travel time variability and reliability in congested traffic networks and other systems, including through probability distributions estimated from moments. Objectives include developing computationally efficient analytical methods, and achieving robustness by reflecting the underlying structure of queuing systems rather than relying on statistical fitting, New deterministic and equilibrium formulae for queue variance are developed, acting also as constraints on estimating time-dependent queues generated by a range of processes, enabling improved accuracy and reliability estimates. New methods for approximating equilibrium and dynamic probability distributions use respectively doubly-nested geometric distributions and exponentially-weighted combinations of exponential and Normal functions, avoiding the need to rely on empirical functions, costly simulation, or equilibrium distributions inappropriate in dynamic cases. For growing queues, corrections are made to the popular sheared approximation, that combines deterministic and Pollaczek-Khinchin equilibrium mean formulae in one time-dependent function. For decaying queues, a new exponential approximation is found to give better results, possibly through avoiding implicit quasi-static assumption in shearing. Predictions for M/M/1 (yield) and M/D/1 (signal) processes applied to 34 oversaturated peaks show good agreement when tested against Markov simulations based on recurrence relations. Looking to widen the range of queues amenable to time-dependent methods, dependence of stochastic signal queues on green period capacity is confirmed by an extended M/D/1 process, for which new formulae for equilibrium moments are obtained and compared with earlier approximations. A simple formulation of queuing on multiple lanes with shared service is developed, two-lane examples with turning movements showing fair match to simulation. The main new methods are implemented in a spreadsheet demonstrator program, incorporating a database of time-sliced peak cases together with a procedure for estimating dynamic probability distributions from moments

Engenharia de sistemas baseada em modelos: um sistema para o tráfego & ambiente

Doutoramento em Gestão IndustrialThe contemporary world is crowded of large, interdisciplinary, complex systems made of other systems, personnel, hardware, software, information, processes, and facilities. The Systems Engineering (SE) field proposes an integrated holistic approach to tackle these socio-technical systems that is crucial to take proper account of their multifaceted nature and numerous interrelationships, providing the means to enable their successful realization. Model-Based Systems Engineering (MBSE) is an emerging paradigm in the SE field and can be described as the formalized application of modelling principles, methods, languages, and tools to the entire lifecycle of those systems, enhancing communications and knowledge capture, shared understanding, improved design precision and integrity, better development traceability, and reduced development risks. This thesis is devoted to the application of the novel MBSE paradigm to the Urban Traffic & Environment domain. The proposed system, the GUILTE (Guiding Urban Intelligent Traffic & Environment), deals with a present-day real challenging problem “at the agenda” of world leaders, national governors, local authorities, research agencies, academia, and general public. The main purposes of the system are to provide an integrated development framework for the municipalities, and to support the (short-time and real-time) operations of the urban traffic through Intelligent Transportation Systems, highlighting two fundamental aspects: the evaluation of the related environmental impacts (in particular, the air pollution and the noise), and the dissemination of information to the citizens, endorsing their involvement and participation. These objectives are related with the high-level complex challenge of developing sustainable urban transportation networks. The development process of the GUILTE system is supported by a new methodology, the LITHE (Agile Systems Modelling Engineering), which aims to lightening the complexity and burdensome of the existing methodologies by emphasizing agile principles such as continuous communication, feedback, stakeholders involvement, short iterations and rapid response. These principles are accomplished through a universal and intuitive SE process, the SIMILAR process model (which was redefined at the light of the modern international standards), a lean MBSE method, and a coherent System Model developed through the benchmark graphical modeling languages SysML and OPDs/OPL. The main contributions of the work are, in their essence, models and can be settled as: a revised process model for the SE field, an agile methodology for MBSE development environments, a graphical tool to support the proposed methodology, and a System Model for the GUILTE system. The comprehensive literature reviews provided for the main scientific field of this research (SE/MBSE) and for the application domain (Traffic & Environment) can also be seen as a relevant contribution.O mundo contemporâneo é caracterizado por sistemas de grande dimensão e de natureza marcadamente complexa, sócio-técnica e interdisciplinar. A Engenharia de Sistemas (ES) propõe uma abordagem holística e integrada para desenvolver tais sistemas, tendo em consideração a sua natureza multifacetada e as numerosas inter-relações que advêm de uma quantidade significativa de diferentes pontos de vista, competências, responsabilidades e interesses. A Engenharia de Sistemas Baseada em Modelos (ESBM) é um paradigma emergente na área da ES e pode ser descrito como a aplicação formal de princípios, métodos, linguagens e ferramentas de modelação ao ciclo de vida dos sistemas descritos. Espera-se que, na próxima década, a ESBM desempenhe um papel fundamental na prática da moderna Engenharia de Sistemas. Esta tese é dedicada à aplicação da ESBM a um desafio real que constitui uma preocupação do mundo actual, estando “na agenda” dos líderes mundiais, governantes nacionais, autoridades locais, agências de investigação, universidades e público em geral. O domínio de aplicação, o Tráfego & Ambiente, caracteriza-se por uma considerável complexidade e interdisciplinaridade, sendo representativo das áreas de interesse para a ES. Propõe-se um sistema (GUILTE) que visa dotar os municípios de um quadro de desenvolvimento integrado para adopção de Sistemas de Transporte Inteligentes e apoiar as suas operações de tráfego urbano, destacando dois aspectos fundamentais: a avaliação dos impactos ambientais associados (em especial, a poluição atmosférica e o ruído) e a divulgação de informação aos cidadãos, motivando o seu envolvimento e participação. Estes objectivos relacionam-se com o desafio mais abrangente de desenvolver redes de transporte urbano sustentáveis. O processo de desenvolvimento do sistema apoia-se numa nova metodologia (LITHE), mais ágil, que enfatiza os princípios de comunicação contínua, feedback, participação e envolvimento dos stakeholders, iterações curtas e resposta rápida. Estes princípios são concretizados através de um processo de ES universal e intuitivo (redefinido à luz dos padrões internacionais), de um método simples e de linguagens gráficas de modelação de referência (SysML e OPDs/OPL). As principais contribuições deste trabalho são, na sua essência, modelos: um modelo revisto para o processo da ES, uma metodologia ágil para ambientes de desenvolvimento baseados em modelos, uma ferramenta gráfica para suportar a metodologia proposta e o modelo de um sistema para as operações de tráfego & ambiente num contexto urbano. Contribui-se ainda com uma cuidada revisão bibliográfica para a principal área de investigação (ES/ESBM) e para o domínio de aplicação (Tráfego & Ambiente)

Safety and Reliability - Safe Societies in a Changing World

The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management - mathematical methods in reliability and safety - risk assessment - risk management - system reliability - uncertainty analysis - digitalization and big data - prognostics and system health management - occupational safety - accident and incident modeling - maintenance modeling and applications - simulation for safety and reliability analysis - dynamic risk and barrier management - organizational factors and safety culture - human factors and human reliability - resilience engineering - structural reliability - natural hazards - security - economic analysis in risk managemen