Development of a Timed Coloured Petri Net Model for Time-of-Day Signal Timing Plan Transitions

In many countries, traffic signal control is one of the most cost effective means of improving urban mobility. Nevertheless, the signal control can be grouped into two principal classes, namely traffic-response and fixed-time. Precisely, a traffic response signal controller changes timing plan in real time according to traffic conditions while a fixed-time signal controller deploys multiple signal timing plans to cater for traffic demand changes during a day. To handle different traffic scenarios via fixed-time signal controls, traffic engineers determine such time-of-day intervals manually using one or two days worth of traffic data. That is, owing to significant variation in traffic volumes, the efficient use of fixed-time signal controllers depends primarily on selecting a number of signal timing plans within a day. In this paper, a Timed Coloured Petri Net (TCPN) formalism was explored to model transition between four signal timing plans of a traffic light control system such that a morning peak signal timing plan handles traffic demand between the hours of 6:00 am and 8:30 am, followed by afternoon I and afternoon II signal timing plans which handle traffic demands from 8:30 am to 3:00 pm and from 3:00 pm to 7:00 pm respectively, while the off peak plan handles traffic demands from 7:00 pm to 9:00 pm. Other hours of the day are ignored since they are characterized by low traffic demands. Keywords: Signal timing plan, Petri nets, Time-of-day, Model, Traffic, Fixed-time

ENHANCED SCHEDULING TRAFFIC LIGHT MODEL USING DISCRETE EVENT SIMULATION FOR IMPROVED SIGNAL TIMING ANALYSIS

Most traffic light today used pre-timed traffic light, traffic light using sensors and traffic light which displaying a countdown timer. However, the existing methods consume a long time of vehicle queuing and waiting the traffic light signals to change, which created congestion at intersection of roads. In this paper, the proposed model enhanced the scheduling traffic light, which simulates the vehicle behaviour based on discrete event simulation and queue theory. Therefore, the simulation becomes more realistic and contributes to accurate outcome. This work focuses on the analysis of the average waiting time for the vehicle in three cases: heavy, medium and low traffic volume. The most optimum traffic signal timing is the one with minimum waiting time for the vehicles. Moreover, the new model solves the critical traffic congestion problem not only in simulation but also in real environment, which drivers take the longest average waiting time is 86 seconds while the shortest average waiting time is 64 seconds at the junction although in heavy traffic congestion. An extensive simulations have been conducted in this work in which a green interval as a control parameter is selected

Evaluating Resilience of Cyber-Physical-Social Systems

Nowadays, protecting the network is not the only security concern. Still, in cyber security, websites and servers are becoming more popular as targets due to the ease with which they can be accessed when compared to communication networks. Another threat in cyber physical social systems with human interactions is that they can be attacked and manipulated not only by technical hacking through networks, but also by manipulating people and stealing users’ credentials. Therefore, systems should be evaluated beyond cy- ber security, which means measuring their resilience as a piece of evidence that a system works properly under cyber-attacks or incidents. In that way, cyber resilience is increas- ingly discussed and described as the capacity of a system to maintain state awareness for detecting cyber-attacks. All the tasks for making a system resilient should proactively maintain a safe level of operational normalcy through rapid system reconfiguration to detect attacks that would impact system performance. In this work, we broadly studied a new paradigm of cyber physical social systems and defined a uniform definition of it. To overcome the complexity of evaluating cyber resilience, especially in these inhomo- geneous systems, we proposed a framework including applying Attack Tree refinements and Hierarchical Timed Coloured Petri Nets to model intruder and defender behaviors and evaluate the impact of each action on the behavior and performance of the system.Hoje em dia, proteger a rede não é a única preocupação de segurança. Ainda assim, na segurança cibernética, sites e servidores estão se tornando mais populares como alvos devido à facilidade com que podem ser acessados quando comparados às redes de comu- nicação. Outra ameaça em sistemas sociais ciberfisicos com interações humanas é que eles podem ser atacados e manipulados não apenas por hackers técnicos através de redes, mas também pela manipulação de pessoas e roubo de credenciais de utilizadores. Portanto, os sistemas devem ser avaliados para além da segurança cibernética, o que significa medir sua resiliência como uma evidência de que um sistema funciona adequadamente sob ataques ou incidentes cibernéticos. Dessa forma, a resiliência cibernética é cada vez mais discutida e descrita como a capacidade de um sistema manter a consciência do estado para detectar ataques cibernéticos. Todas as tarefas para tornar um sistema resiliente devem manter proativamente um nível seguro de normalidade operacional por meio da reconfi- guração rápida do sistema para detectar ataques que afetariam o desempenho do sistema. Neste trabalho, um novo paradigma de sistemas sociais ciberfisicos é amplamente estu- dado e uma definição uniforme é proposta. Para superar a complexidade de avaliar a resiliência cibernética, especialmente nesses sistemas não homogéneos, é proposta uma estrutura que inclui a aplicação de refinamentos de Árvores de Ataque e Redes de Petri Coloridas Temporizadas Hierárquicas para modelar comportamentos de invasores e de- fensores e avaliar o impacto de cada ação no comportamento e desempenho do sistema

Manufacturing Systems Line Balancing using Max-Plus Algebra

In today\u27s dynamic environment, particularly the manufacturing sector, the necessity of being agile, and flexible is far greater than before. Decision makers should be equipped with effective tools, methods, and information to respond to the market\u27s rapid changes. Modelling a manufacturing system provides unique insight into its behavior and allows simulating all crucial elements that have a role in the system performance. Max-Plus Algebra is a mathematical tool that can model a Discrete Event Dynamic System in the form of linear equations. Whereas Max-Plus Algebra was introduced after the 1980s, the number of studies regarding this tool and its applications is fewer than regarding Petri Nets, Automata, Markov process, Discrete Even Simulation and Queuing models. Consequently, Max-Plus Algebra needs to be applied and tested in many systems in order to explore hidden aspects of its function and capabilities. To work effectively; the production/assembly line should be balanced. Line balancing is one of the manufacturing functions that tries to divide work equally across the production flow. Car Headlight Manufacturing Line as a Discrete Manufacturing System is considered which is a combination of manufacturing and assembly lines composed of different stations. Seven system scenarios were modeled and analyzed using Max-Plus to balance the car headlights production line. Key Performance Indicators (KPIs) are used to compare the various scenarios including Cycle Time, Average Deliver Rate, Total Processing Lead Time, Stations\u27 Utilization Rate, Idle Time, Efficiency, and Financial Analysis. FlexSim simulation software is used to validate the Max-Plus models results and its advantages and drawbacks compared with Max-Plus Algebra. This study is a unique application of Max-Plus Algebra in line balancing of a manufacturing system. Moreover, the problem size of the considered model is at least twice (12 stations) that of previous studies. In the matter of complexity, seven different scenarios are developed through the combination of parallel stations and buffers. Due to that the last scenario is included four parallel stations plus two buffers Based on the findings, the superiority of scenario 7 compared to other scenarios is proved due to its lowest system delivering first output time (14 seconds), best average delivery rate (24.5 seconds), shortest cycle time (736 seconds), shortest total processing lead time (11,534 seconds), least percentage of idle time (12%), lowest unit cost ($6.9), and highest efficiency (88%). However, Scenario 4 has the best utilization rate at 75%

Safety‐oriented discrete event model for airport A‐SMGCS reliability assessment

A detailed analysis of State of the Art Technologies and Procedures into Airport Advanced-Surface Movement Guidance and Control Systems has been provided in this thesis, together with the review ofStatistical Monte Carlo Analysis, Reliability Assessment and Petri Nets theories. This practical and theoretical background has lead the author to the conclusion that there is a lack of linkage in between these fields. At the same of time the rapid increasing of Air Traffic all over the world, has brought in evidence the urgent need of practical instruments able to identify and quantify the risks connected with Aircraft operations on the ground, since the Airport has shown to be the actual ‘bottle neck’ of the entire Air Transport System. Therefore, the only winning approach to such a critical matter has to be multi-disciplinary, sewing together apparently different subjects, coming from the most disparate areas of interest and trying to fulfil the gap. The result of this thesis work has come to a start towards the end, when a Timed Coloured Petri Net (TCPN) model of a ‘sample’ Airport A-SMGCS has been developed, that is capable of taking into account different orders of questions arisen during these recent years and tries to give them some good answers. The A-SMGCS Airport model is, in the end, a parametric tool relying on Discrete Event System theory, able to perform a Reliability Analysis of the system itself, that: • uses a Monte Carlo Analysis applied to a Timed Coloured Petri Net, whose purpose is to evaluate the Safety Level of Surface Movements along an Airport • lets the user to analyse the impact of Procedures and Reliability Indexes of Systems such as Surface Movement Radars, Automatic Dependent Surveillance-Broadcast, Airport Lighting Systems, Microwave Sensors, and so on… onto the Safety Level of Airport Aircraft Transport System • not only is a valid instrument in the Design Phase, but it is useful also into the Certifying Activities an in monitoring the Safety Level of the above mentioned System with respect to changes to Technologies and different Procedures.This TCPN model has been verified against qualitative engineering expectations by using simulation experiments and occupancy time schedules generated a priori. Simulation times are good, and since the model has been written into Simulink/Stateflow programming language, it can be compiled to run real-time in C language (Real-time workshop and Stateflow Coder), thus relying on portable code, able to run virtually on any platform, giving even better performances in terms of execution time. One of the most interesting applications of this work is the estimate, for an Airport, of the kind of A-SMGCS level of implementation needed (Technical/Economical convenience evaluation). As a matter of fact, starting from the Traffic Volume and choosing the kind of Ground Equipment to be installed, one can make predictions about the Safety Level of the System: if the value is compliant with the TLS required by ICAO, the A-SMGCS level of Implementation is sufficiently adequate. Nevertheless, even if the Level of Safety has been satisfied, some delays due to reduced or simplified performances (even if Safety is compliant) of some of the equipment (e.g. with reference to False Alarm Rates) can lead to previously unexpected economical consequences, thus requiring more accurate systems to be installed, in order to meet also Airport economical constraints. Work in progress includes the analysis of the effect of weather conditions and re-sequencing of a given schedule. The effect of re-sequencing a given schedule is not yet enough realistic since the model does not apply inter arrival and departure separations. However, the model might show some effect on different sequences based on runway occupancy times. A further developed model containing wake turbulence separation conditions would be more sensitive for this case. Hence, further work will be directed towards: • The development of On-Line Re-Scheduling based on the available actual runway/taxiway configuration and weather conditions. • The Engineering Safety Assessment of some small Italian Airport A-SMGCSs (Model validation with real data). • The application of Stochastic Differential Equations systems in order to evaluate the collision risk on the ground inside the Place alone on the Petri Net, in the event of a Short Term Conflict Alert (STCA), by adopting Reich Collision Risk Model. • Optimal Air Traffic Control Algorithms Synthesis (Adaptive look-ahead Optimization), by Dynamically Timed Coloured Petri Nets, together with the implementation of Error-Recovery Strategies and Diagnosis Functions

A virtual factory for smart city service integration

Tese de Doutoramento em Informática (MAP-i)In the context of smart cities, governments are investing efforts on creating public value through the development of digital public services (DPS) focusing on specific policy areas, such as transport. Main motivations to deliver DPS include reducing administrative burdens and costs, increasing effectiveness and efficiency of government processes, and improving citizens’ quality of life through enhanced services and simplified interactions with governments. To ensure effective planning and design of DPS in a given domain, governments face several challenges, like the need of specialized tools to facilitate the effective planning and the rapid development of DPS, as well as, tools for service integration, affording high development costs, and ensuring DPS conform with laws and regulations. These challenges are exacerbated by the fact that many public administrations develop tailored DPS, disregarding the fact that services share common functionality and business processes. To address the above challenges, this thesis focuses on leveraging the similarities of DPS and on applying a Software Product Line (SPL) approach combined with formal methods techniques for specifying service models and verifying their behavioural properties. In particular, the proposed solution introduces the concept of a virtual factory for the planning and rapid development of DPS in a given smart city domain. The virtual factory comprises a framework including software tools, guidelines, practices, models, and other artefacts to assist engineers to automate and make more efficient the development of a family of DPS. In this work the virtual factory is populated with tools for government officials and software developers to plan and design smart mobility services, and to rapidly model DPS relying on SPLs and components-base development techniques. Specific contributions of the thesis include: 1) the concept of virtual factory; 2) a taxonomy for planning and designing smart mobility services; 3) an ontology to fix a common vocabulary for a specific family of DPS; 4) a compositional formalism to model SPLs, to serve as a specification language for DPS; and 5) a variable semantics for a coordination language to simplify coordination of services in the context of SPLs.No contexto das cidades inteligentes, os governos investem esforços na criação de valor público através do desenvolvimento de serviços públicos digitais (DPS), concentrandose em áreas políticas específicas, como os transportes. As principais motivações para entregar o DPS incluem a redução de custos administrativos, o aumento da eficácia dos processos do governo e a melhoria da qualidade de vida dos cidadãos através de serviços melhorados e interações simplificadas com os governos. Para garantir um planeamento efetivo do DPS num determinado domínio, os governos enfrentam vários desafios, como a necessidade de ferramentas especializadas para facilitar o planeamento eficaz e o rápido desenvolvimento do DPS, bem como ferramentas para integração de DPS, reduzindo altos custos de desenvolvimento e garantindo que os DPS estejam em conformidade com as leis e regulamentos. Esses desafios são exacerbados pelo fato de que muitas administrações públicas desenvolvem o DPS sob medida, desconsiderando o fato de que os serviços compartilham funcionalidade e processos de negócios comuns. Para enfrentar os desafios, esta tese concentra-se em aproveitar as semelhanças dos DPS aplicando uma abordagem de Software Product Lines (SPL) combinada com métodos formais para especificar modelos de DPS e verificar propriedades. Em particular, introduz o conceito de uma fábrica virtual (VF) para o planeamento e desenvolvimento rápido de DPS num domínio de cidade inteligente. A VF compreende ferramentas de software, diretrizes, modelos e outros artefatos para auxiliar os engenheiros a automatizar e tornar mais eficiente o desenvolvimento de uma família de DPS. Neste trabalho, a VF é preenchida com ferramentas para várias partes para planear e projetar serviços de mobilidade inteligente (MI), e modelar rapidamente o DPS com base em SPLs e técnicas de desenvolvimento baseadas em componentes. Contribuições específicas da tese incluem: 1) o conceito de VF; 2) uma taxonomia para planear serviços de MI; 3) uma ontologia para fixar um vocabulário comum para uma família específica de DPS; 4) um formalismo composicional para modelar SPLs, e servir como uma linguagem de especificação para DPS; e 5) uma semântica variável para uma linguagem de coordenação para simplificar a coordenação.This work was funded by FCT – Foundation for Science and Technology, the Portuguese Ministry of Science, Technology and Higher Education, through the Operational Programme for Human Capital (POCH). Grant reference: PD/BD/52238/201

Curr Epidemiol Rep

Purpose of review:Road traffic injuries are one of the leading causes of death in the U.S. and globally. We introduce the Safe Systems approach as a promising paradigm for road safety practice and describe how systems thinking tools can help bridge the gap between the current status quo and a Safe Systems approach.Recent findings:Systems thinking tools can help us align with a Safe Systems approach by identifying latent risks in the transportation system, examining factors that coalesce to produce high travel speeds and kinetic energy transfer, and supporting safety prioritization through goal alignment.Summary:The Safe Systems approach represents a significant change in the way we have historically designed transportation systems; it puts safety at the forefront and calls for designing a system that accounts for human fallibility. Operationalizing holistic Safe Systems concepts may be difficult, but systems thinking tools can help. Systems thinking tools provide a common language for individuals from diverse disciplines and sectors to express their unique understanding of the interconnected factors shaping road safety problems and support discussions about potential solutions that align with a Safe Systems approach.R49 CE002479/CE/NCIPC CDC HHS/United States2021-01-15T00:00:00Z34136335PMC8205420988