Dissertations / Theses on the topic 'Traffic flow'

Paper 1 Electronic version of an article published asJournal of Hyperbolic Differential Equations (JHDE) Year: 2008 Vol: 5 Issue: 1 (March 2008) Page: 45 - 63, DOI:10.1142/S0219891608001428 © [copyright World Scientific Publishing Company] http://ejournals.ebsco.com/Direct.asp?AccessToken=8PUU3U4V0W9F3OY0909K09P3FOXYVWNOW&Show=Object&msid=943592237

The advancement in computational intelligence and computational power and the explosionof traffic data continues to drive the development and use of Intelligent TransportSystem and smart mobility applications. As one of the fundamental components of IntelligentTransport Systems, traffic flow prediction research has been advancing from theclassical statistical and time-series based techniques to data–driven methods mainly employingdata mining and machine learning algorithms. However, significant number oftraffic flow prediction studies have overlooked the impact of road network topology ontraffic flow. Thus, the main objective of this research is to show that traffic flow predictionproblems are not only affected by temporal trends of flow history, but also by roadnetwork topology by developing prediction methods in the spatio-temporal.In this study, time–series operators and data mining techniques are used by definingfive partially overlapping relative temporal offsets to capture temporal trends in sequencesof non-overlapping history windows defined on stream of historical record of traffic flowdata. To develop prediction models, two sets of modeling approaches based on LinearRegression and Support Vector Machine for Regression are proposed. In the modelingprocess, an orthogonal linear transformation of input data using Principal ComponentAnalysis is employed to avoid any potential problem of multicollinearity and dimensionalitycurse. Moreover, to incorporate the impact of road network topology in thetraffic flow of individual road segments, shortest path network–distance based distancedecay function is used to compute weights of neighboring road segment based on theprinciple of First Law of Geography. Accordingly, (a) Linear Regression on IndividualSensors (LR-IS), (b) Joint Linear Regression on Set of Sensors (JLR), (c) Joint LinearRegression on Set of Sensors with PCA (JLR-PCA) and (d) Spatially Weighted Regressionon Set of Sensors (SWR) models are proposed. To achieve robust non-linear learning,Support Vector Machine for Regression (SVMR) based models are also proposed.Thus, (a) SVMR for Individual Sensors (SVMR-IS), (b) Joint SVMR for Set of Sensors(JSVMR), (c) Joint SVMR for Set of Sensors with PCA (JSVMR-PCA) and (d) SpatiallyWeighted SVMR (SWSVMR) models are proposed. All the models are evaluatedusing the data sets from 2010 IEEE ICDM international contest acquired from TrafficSimulation Framework (TSF) developed based on the NagelSchreckenberg model.Taking the competition’s best solutions as a benchmark, even though different setsof validation data might have been used, based on k–fold cross validation method, withthe exception of SVMR-IS, all the proposed models in this study provide higher predictionaccuracy in terms of RMSE. The models that incorporated all neighboring sensorsdata into the learning process indicate the existence of potential interdependence amonginterconnected roads segments. The spatially weighted model in SVMR (SWSVMR) revealedthat road network topology has clear impact on traffic flow shown by the varyingand improved prediction accuracy of road segments that have more neighbors in a closeproximity. However, the linear regression based models have shown slightly low coefficientof determination indicating to the use of non-linear learning methods. The resultsof this study also imply that the approaches adopted for feature construction in this studyare effective, and the spatial weighting scheme designed is realistic. Hence, road networktopology is an intrinsic characteristic of traffic flow so that prediction models should takeit into consideration.

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Network Behavior Analysis (NBA) is a technique to enhance network security by passively monitoring aggregate traffic patterns and noting unusual action or departures from normal operations. The analysis is typically performed offline, due to the huge volume of input data, in contrast to conventional intrusion prevention solutions based on deep packet inspection, signature detection, and real-time blocking. After establishing a benchmark for normal traffic, an NBA program monitors network activity and flags unknown, new, or unusual patterns that might indicate the presence of a potential threat. NBA also monitors and records trends in bandwidth and protocol use. Computer users in the Department of Defense (DoD) operational networks may use Hypertext Transport Protocol (HTTP) to stream video from multimedia sites like youtube.com, myspace.com, mtv.com, and blackplanet.com. Such streaming may hog bandwidth, a grave concern, given that increasing amounts of operational data are exchanged over the Global Information Grid, and introduce malicious viruses inadvertently. This thesis develops an NBA solution to identify and estimate the bandwidth usage of HTTP streaming video traffic entirely from flow records such as Cisco's NetFlow data.

Traffic congestion is a common problem in larger cities. Time consuming queues affects both the humans and the environment. This report investigate show to improve the traffic flow in a future scenario where only autonomous vehicles are present. The methodology was to construct traffic networks on routes where congestion is a problem. This was done with three different Stockholm routes. The networks were transformed into graphs and then the maximal flow was calculated by Edmond Karp’s flow algorithm. The result proves that this type of route planning is a concept that can be used in future studies to decrease congestion. This is due to the fact that the flow increase was much larger than both the increase in travelled distance and time.
Trafikstockning är ett vanligt förekommande problem i större städer. Tidskrävande köer påverkar både människan och miljön. I denna rapport studeras hur man kan förbättra trafikflödet i ett framtida scenario där endast automatiserade fordon är tillgängliga. Metoden var att konstruera ett nätverk utav vägar där trängsel är ett problem. Detta gjordes för tre olika rutter i Stockholm. Nätverken transformerades sedan till grafer och det maximala flödet beräknades med hjälp av Edmond Karps flödesalgoritm. Resultatet visar på att denna typ av ruttoptimering skulle kunna användas i framtida studier för att minska trafikstockning i och med att flödesökningen var betydligt större än både ökningen i avstånd och tid.

The general objective of this research was to examine the space/time distribution of traffic platoons over a long stretch of roadway with conditions predominant for the southern Arizona urban area. Two sites were chosen for data collection. Both traffic links were one mile long between two successive traffic signals and both were typical of the local low-friction traffic flow conditions. All data were recorded by observers using 20-channel Esterline-Angus recorders. The specifics of the data collection method permitted studying only variables such as the lane of travel, traffic composition, platoon size, traffic volume and the influence of an uphill gradient on platoon behavior. The investigated platoons remained clearly bunched as they progressed downstream along the researched traffic links. The research indicates that it would take much more than a mile (available distance) for the vehicles in the platoon to reach free-flow conditions.

ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California
Telemetry receivers must typically be located so that obstacles do not block the signal path. This can be challenging in geometrically complex indoor environments, such as factories, health care facilities, or offices. An accurate method for estimating the paths followed by typical telemetry transmitters in these environments can assist in system planning. It may be acceptable to provide marginal coverage to areas which are rarely visited, or areas which transmitters quickly transit. This paper discusses the use of the ant colony optimization and its application to the telemetry system planning problem.

In aviation, the demand for air traffic grows at a higher rate than the capacity. As the demand is predicted to continue to grow also in the future, so is the problem of capacity shortage. If the capacity cannot match the demand, it will result in congestion and delay. There are numerous factors that limit the capacity both on airside and landside, for example the runway capacity, noise restrictions, the environment surrounding the airport etc. Actors such as airlines, ground service companies, ICAO and IATA also affect and are affected by the available capacity. When planning opening of new airports or in case of changes in the location and size of the airports, the requirement for, as well as the currently available capacity must be examined. Previous studies regarding key limiting factors to air traffic capacity, address different constraints, but lack a comprehensive view. A compilation of air traffic constraints would therefore be a valuable tool in airport planning when capacity demand changes. The aim of this thesis was to identify key limiting factors and see how they affect air traffic. This thesis analyses the importance of different limiting factors in respect to the level of significance to which previous research has acknowledged the different constraints. To compliment the literature review, professionals in airport planning were interviewed. The result from the literature review as well as the interviews showed that the major limiting factor to air traffic capacity is the runway. The runway was also the factor that was affecting as well was affected by other limiting factors. Previous literature considered wake vortex to be the second most important constraint whereas the interviewees considered stands to be the runner up limiting factor. In conclusion, this thesis showed that the runway is the most important limiting factor to air traffic capacity. The thesis also showed that different limiting factors are closely linked to each other. For an overall understanding of air traffic capacity constraints and how these constraints affect air traffic flow, it is essential to understand the interaction between the limiting factors.

Les retards et les émissions CO2 sont des sujets critiques dans l’industrie aéronautique. Les principales sources de retard sont le déséquilibre entre la demande et la capacité, la dotation en personnel des contrôleurs du traffic aérien et les conditions météorologiques extrêmes. Dans certains cas, les compagnies aériennes peuvent choisir d’augmenter la vitesse de l’avion au delà de celle programmée, ce qui engendre une augmentation des émissions. Plusieurs projets ont été lancés pour améliorer le partage d’informations et, par conséquent, la prise de décision au profit de tous les acteurs ou toutes les parties prenantes de l’aviation et réduire les retards et les émissions.Dans cette thèse de doctorat, nous visons à étudier le problème de la gestion des flux du trafic aérien (Air Traffic Flow Management (ATFM)) du point de vue de la recherche opérationnelle / management des opérations. Nous étudions le modèle ATFM largement utilisé dans la littérature et l’analysons. Nous corrigeons les lacunes de formulation de la littérature et étendons la conception du réseau et les fonctionnalités considérées pour atteindre une meilleure représentation du réseau réel. Dans cette extension, nous considérons plusieurs types de vols et plusieurs décisions, comme le changement de trajectoire et d’aéroport d’atterrissage. L’objectif de de ce travail peut être résumé dans les points suivants.(1) Étudier l’impact de la centralisation du processus de prise de décision dans le problème ATFM par rapport à la situation actuelle où les décisions de l’autorité ATFM et des compagnies aériennes sont prises indépendamment.1(2) Analyser l’équité inter-vols et inter-compagnies dans le problème ATFM.(3) Construire un modèle de capacité météorologique de décision pour les aéroports et développer des arbres de scénarios pour les réseaux ATFM stochastiques basés sur des données réelles.(4) Intégrer la configuration dynamique de l’espace aérien dans le problème ATFM et analyser son impact.(5) Tenir compte des émissions CO2 et des différents types de carburant dans l’ATFM.Nous développons dous cette thèse plusieurs extensions du modèle ATFM pour analyser ces problématiques. Tout d’abord, nous proposons un modèle ATFM déterministe qui centralise les décisions de l’autorité ATFM et des compagnies aériennes, et qui considère différentes options de réacheminement. Ensuite, nous formulons un modèle ATFM stochastique qui tient compte des incertitudes météorologiques du traffic aérien. La relation météo-capacité et les arbres de scénarios stochastiques sont élaborés à l’aide des rapports d’aérodrome météorologiques, de la base de données AirportCorner et de la technique de regroupement des k-means. Ensuite, nous nous concentrons sur l’optimisation de la configuration de l’espace aérien en même temps que le problème ATFM en minimisant la capacité totale de l’espace aérien inutilisé et le coût total du réseau. Enfin, nous intégrons les émissions CO2 dans la modélisation ATFM à travers un modèle d’optimisation bi-objectif. Le modèle permet d’étudier l’impact des émissions de CO2 sur le coût du réseau et l’effet du type de combustible sur les décisions du réseau. Les modèles développés sont résolus en utilisant l’approche exacte, et dans le cas de temps de calcul longs, une heuristique du type fix-and-relax.Les modèles proposés peuvent aider les décideurs à analyser l’impact des décisions à prendre sur le réseau et les acteurs impliqués. Par conséquent, les conséquences et les coûts associés pourront être calculés. En outre, ces modèles aident les décideurs à affiner et à vérifier les résultats de plusieurs projets et initiatives ATFM. Ils suggèrent également aux décideurs comment les plans de vol peuvent être mis à jour en cas de perturbation du réseau et les coûts associés aux changements
Delays and emissions are critical topics in the aviation industry. The major delay sources are imbalanced demand and capacity, air traffic controller staffing, and severe weather conditions. In some cases, flights can choose to fly at a higher speed than the scheduled one, which increases emissions. Moreover, several projects have been initiated to improve information sharing, and consequently, decision making in order to benefit all aviation parties and reduce delays and emissions.In this Ph.D. thesis, we aim at studying the air traffic flow management (ATFM) problem from an operations research/operations management perspective. We study the ATFM model, a widely used model in the literature, and analyze it. We correct the formulation deficiencies, and we extend the network design and the considered features to reach a better representation of the real-life network. In this extension, we consider several types of flights and several decision options, such as changing the path or the landing airport. The objectives of this research can be summarized in the following points.(1) To study the impact of centralizing the decision-making process in the ATFM problem compared to the current situation where decisions by ATFM authority and airlines are made independently.(2) To analyze the inter-flight and inter-airline fairness in the ATFM problem.(3) To construct a weather-capacity model for airports and develop scenario trees for stochastic ATFM networks based on real data.(4) To integrate dynamic airspace configuration in the ATFM problem and to analyze the impact.(5) To account for CO2 emissions and different fuel types in the ATFM.Therefore, we develop several extensions to the ATFM model to accommodate these issues. First, we propose a deterministic ATFM model that centralizes the decisions of the ATFM authority and the airlines, and that considers different rerouting options. Then, we formulate a stochastic ATFM model that accounts for airports' weather uncertainties. The weather-capacity relationship and the stochastic scenario trees are developed using meteorological aerodrome reports, the AirportCorner database, and the k-means clustering technique. After that, we focus on optimizing the airspace configuration simultaneously with the ATFM problem by minimizing the total unused airspace capacity and the total network cost. Finally, we integrate the CO2 emissions in the ATFM model through a bi-objective optimization approach. The model is used to study the CO2 emissions' impact on the network's cost and the effect of fuel type on the network decisions. The developed models are solved using the exact approach, and in the case of long computational times, a fix-and-relax heuristic is used.The proposed models can help decision-makers through analyzing the impact of the decisions to be made on the network and the stakeholders involved. Therefore, the consequences and the associated costs can be calculated. In addition, these models help decision-makers fine-tune and verify findings of several ATFM projects and initiatives. They also suggest to decision makers how flight plans can be updated in cases of network disturbance and the associated costs of the changes

Speed - density relationship is the foundation of the traffic flow theory and transportation engineering. It represents the mathematical relationship among the three significant traffic parameters - traffic flow, speed and density. Since the speed-density relationship was first introduced by Greenshields in 1935, the development of this relationship has been greatly increased and there are numerous models to represent the relationship (e.g. Greenberg model; Underwood model; Newell model; Northwestern model; Wang et al. model). The speed-density relationship function is expected to have both empirical accuracy and mathematical elegance. It was long believed that single-regime models could not well represent all traffic states ranging from free flow conditions to jam conditions. In this thesis, field data was collected on the Georgia State Route 400, I-80, US101 in USA and M1 Motorway in AU. According to the literature, existing single-regime deterministic models calibrated by the least square method (LSM) could not fit the empirical data consistently well throughout the whole traffic state, especially in congested conditions. However, we found that the inaccuracy of the deterministic models is not caused solely by their functional forms, but also by the sample selection bias. It is because the observational database has poor quality as most of the data points refer to free flow condition. The calibrated models are likely to be dominated by free flow conditions, which results in poor performances for congested traffic states. Therefore, we propose two methods to resolve the sample selection bias. Firstly, the weighted least square method (WLSM) was used to solve the sample bias problems. We proposed three weighting methods to calibrate six single-regime deterministic models. According to our calibration results, these models, used the WLSM, to fit the dataset reasonably as it well represented all traffic states ranging from free flow conditions to traffic jam conditions. Furthermore, model validation part provides the results of relative errors, mean square error (MSE), root-mean-square deviation (RMSE). In addition, a theoretical investigation revealed the deficiency of LSM when conducted. The results showed that the inaccuracy of single regime speed-density models was not caused solely by their functional forms, but also by sample selection bias. For the other method, we used a fundamentally different approach that was able to yield very similar and consistent results with the previous WLSM model. The proposed approach applies reproducible sample generation to convert the observational data to experimental data. Then, the traditional least square method (LSM) could subsequently be applied to calibrate accurate traffic flow fundamental diagrams. Two reproducible sample generation approaches were proposed in this research. Based on our analysis, the first approach was somewhat affected by outliers and the second approach was more robust in dealing with potential outliers. As per our data, speed possesses a high degree of randomness for a given traffic state, which is more appropriate to be represented by random variables than deterministic numbers. The study then proceeds to propose a probabilistic speed-density relationship to represent the variance of speed by a given density value. In this section, we applied a new calibration approach to generate stochastic traffic flow fundamental diagrams. We first proved that the percentile based fundamental diagrams were obtainable based on the proposed model. We further proved that the proposed model had continuity, differentiability and convexity properties so that it could be easily solved by Gauss-Newton method. By selecting different percentile values from 0 to 1, the speed distributions at any given densities could be derived. The calibrated speed distributions perfectly fitted the GA400 dataset. This proposed methodology has wide applications. First, new approaches can be proposed to evaluate the performance of calibrated fundamental diagrams by taking into account not only the residual but also ability to reflect the stochasticity of samples. Secondly, stochastic fundamental diagrams can be used to develop and evaluate traffic control strategies. In particular, the proposed stochastic fundamental diagram is applicable to model and to optimize the connected and automated vehicles at the macroscopic level with an objective to reduce the stochasticity of traffic flow. Last but not the least, this proposed methodology can be applied to generate the stochastic models for most regression models with scattered samples.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
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Thesis (M.S.)--West Virginia University, 2006.
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Due to it being increasingly common that users' data is encrypted, the Internet service providers today find it difficult to adapt their service for the users' needs. Previously popular methods of classifying users data does not work as well today and new alternatives is therefore desired to give the users an optimal experience.This study focuses specifically on classifying data flows into video and non-video flows with the use of machine learning algorithms and with a focus on runtime performance. In this study the tested algorithms are created in Python and then exported into a C code implementation, more specifically the random forest and the gradient boosting trees algorithm.The goal is to find the algorithm with the fastest classification time relative to its accuracy, making the classification as fast as possible and the classification model to require as little space as possible.The results show that random forest was significantly faster at classification than gradient boosting trees, with initial tests showing it to be roughly 7 times faster after compiler optimization. After optimizing the C code random forest could classify more than 250,000 data flows each second with decent accuracy. Neither of the two algorithms required a lot of space (<3 megabyte).
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Thesis (Honors)--Ohio State University, 2005
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Avui dia un considerable nombre d’infraestructures del transport aeri tenen problemes de congestió. Aquesta situació es veu empitjorada amb l’increment de trànsit existent i amb la seva densitat deguda al sistema de hub i spoke utilitzat per les companyies aèries. Aquesta congestió es veu agreujada puntualment per disminucions de capacitat per causes com la meteorologia. Per mitigar aquests desequilibris, normalment són implementades mesures de gestió del flux de transit aeri (ATFM), sent el retard a l’aeroport d’origen una de les més utilitzades. Assignant retard previ a l’enlairament, el trànsit d’arribada és repartit durant un interval de temps superior i les arribades es distribueixen. Malgrat això, la predicció de quan aquestes reduccions de capacitat es solucionaran una tasca dificultosa. Això comporta que es defineixin regulacions que són més llargues del necessari i per tant, porta a la realització de retard innecessari i al desaprofitament de capacitat. La definició de trajectòries precises ofereix noves oportunitats per gestionar aquests desequilibris. Una tècnica prometedora és la utilització de variacions de velocitat durant el creuer. Generalment, es considera que volar més lent que la velocitat de màxim abast (MRC) no és eficient. En aquesta tesis es presenta una nova aproximació. Quan les aerolínies planifiquen els seus vols, consideren el cost del temps junt amb el del combustible. Per tant, és habitual seleccionar velocitats més ràpides que MRC. Així és possible volar més lent de la velocitat de MRC tot mantenint el mateix consum inicialment planificat. Aquest retard realitzat a l’aire pot ser considerat a la fase pre-tàctica per dividir el retard assignat a un vol en retard a terra i retard a l’aire durant el creuer. Amb aquesta estratègia, el retard és absorbit de manera gradual durant el vol fent servir el mateix combustible que inicialment planificat. Si la regulació es cancel•la abans del que estava planificat inicialment, els vols que estan a l’aire es troben en una situació més favorable per tal de recuperar part del retard. La present tesis es centra en l’estudi d’aquest concepte. En primer lloc, s’ha realitzat un estudi de la relació entre el combustible utilitzat i el temps de vol quan es modifica la velocitat nominal de creuer. A continuació, s’ha definit i analitzat el retard que pot ser realitzat sense incorre en un consum extra de combustible en l’absència i en la presencia de vent. També s’ha considerat i analitza la influència de triar un nivell de vol diferent del planificat inicialment i la utilització de combustible extra per tal d’obtenir major quantitat de retard. Els resultats mostren que per vols de curt i mitja distància, la quantitat de retard realitzable és d’entorn a 5 minuts, aquesta quantitat augmenta a uns 25 minuts per vols de llarg recorregut. El nivell de vol s’ha identificat com un dels paràmetres principals que afecten a la quantitat de retard que pot ser absorbit a l’aire. A continuació es presenta l’aplicació de la tècnica a regulacions d’ATFM realistes, i particularment a ground delay programs (GDP). Per tal de mostrar resultats que siguin significatius, els GDPs implementats en 2006 en el espai aeri nord-americà han sigut analitzats. Han sigut detalladament estudiats escenaris als aeroports de San Francisco, Newark i Chicago. Aquests tres aeroports van ser els que van declarar més GDPs durant el 2006 i per la seva situació geogràfica presenten trànsits amb diferents característiques. Per tal de considerar el trànsit s’ha utilitzat dades de la Federal Aviation Administration i característiques aerodinàmiques i de consum realistes provinents d’Airbus. Finalment, la tesis presenta l’efecte d’utilitzar radis d’exempció en els programes de regulació de trànsit i l’ ús de polítiques de priorització de vols diferents a la utilitzada actualment (ration-byschedule). Per concloure, s’ha realitzat una breu discussió sobre l’impacte d’aquesta estratègia en la gestió del trànsit aeri.
Nowadays, many air transport infrastructures suffer from congestion. This situation is worsened by a continuous increase in traffic, and, traffic density due to hub and spoke systems. Weather is one of the main causes which leads to punctual capacity reduction. To mitigate these imbalances, air traffic flow management (ATFM) initiatives are usually undertaken, ground delay at the origin airport being one of the main ones used. By assigning delay on ground at the departure airport, the arrival traffic is spread out and the arrivals are metered at the congested infrastructure. However, forecasting when these capacity drops will be solved is usually a difficult task. This leads to unnecessarily long regulations, and therefore to the realisation of unnecessary delay and an underuse of the capacity of the infrastructures.The implementation of precise four dimension trajectories, envisaged in the near future, presents new opportunities for dealing with these capacity demand imbalances. In this context, a promising technique is the use of speed variation during the cruise. Generally, it is considered that flying slower than the maximum range speed (MRC) is neither efficient nor desirable. In this dissertation a new approach is presented. When airlines plan their flights, they consider the cost of time along with the cost of fuel. It is therefore common practice to select speeds that are faster than MRC.Thus, it is possible to fly slower than MRC while maintaining fuel consumption as initially planned. This airborne delay can be considered at a pre-tactical phase to divide the assigned air traffic flow management delay between ground and airborne delay. With this strategy, the delay is absorbed gradually during the flight using the same fuel as initially planned, but with the advantage that, if the regulation is cancelled before planned, the flights which are already airborne are in a better position to recover part of their assigned delay.This dissertation focuses on the study of this concept. Firstly, a study of the trade-off existing between fuel consumption and flight time, when modifying the nominal cruise speed, is presented. Secondly, the airborne delay that can be realised without incurring extra fuel consumption is defined and assessed in the absence and presence of wind. The influence of selecting a different flight level than initially planned, and the use of extra fuel consumption to obtain higher delay, are also considered and analysed. Results show that for short and mid-range flights around 5 minutes of airborne delay can be realised, while for longer flights this value increases up to around 25 minutes. The flight level is identified as one of the main parameters which affect the amount of airborne delay realisable.Then, the application of the suggested cruise speed reduction on realistic ATFM initiatives, and, in particular, on ground delay programs (GDP) in the United States, is presented. In order to obtain significant results, the GDPs implemented in North American airspace during 2006 are analysed. Scenarios for San Francisco International, Newark Liberty International and Chicago O'Hare International are studied in detail, as these airports were the ones where the most GDPs were implemented in 2006. In addition, due to their location, they present different traffic behaviours. In order to consider the traffic, Federal Aviation Administration data and the aerodynamics and fuel consumption characteristic form Airbus are used.Finally, the use of radius of exemption in the GPDs and the use of ration policies different from the operative ration-by-schedule, are also analysed. To conclude, a brief discussion about the impact of this speed reduction strategy on the air traffic management is presented.
Hoy en día un número considerable de infraestructuras del transporte aéreo tienen problemas de congestión. Esta situación se ve empeorada por el incremento de tráfico existente y por su densidad producida por el sistema de hub y spoke utilizado por las compañías aéreas. Esta congestión se ve agravada puntualmente por disminuciones de capacidad debidas a causas como la meteorología. Para mitigar estos desequilibrios, normalmente se implementan medidas de gestión del tráfico aéreo (ATFM), siendo el retraso en el aeropuerto de origen una de las más utilizadas. Asignando retraso en tierra previo al despegue, el tráfico de llegada se distribuye durante un intervalo mayor de tiempo y se controlan las llegadas. Pese a esto, la predicción de cuando estas reducciones de capacidad se solventarán es generalmente una tarea compleja. Por esto, se suelen definir regulaciones durante un periodo de tiempo superior al necesario, comportando la asignación y realización de retraso innecesario y el desaprovechamiento de las infraestructuras. La definición de trayectorias precisas permite nuevas oportunidades para gestionar estos desequilibrios. Una técnica prometedora es el uso de variaciones de velocidad durante el crucero. Suele considerarse que volar más lento que la velocidad de máximo alcance (MRC) no es eficiente. En esta tesis se presenta una nueva aproximación. Cuando las aerolíneas planifican sus vuelos consideran el coste del tiempo junto con el del combustible. Por consiguiente, es una práctica habitual seleccionar velocidades mas rápidas que MRC. Así es posible volar mas lento que la velocidad de MRC manteniendo el mismo consumo que el inicialmente planificado. Este retraso realizable en el aire puede ser considerado en la fase pre-táctica para dividir el retraso asignado entre retraso en tierra y retraso durante el crucero. Con esta estrategia, el retraso es absorbido de manera gradual durante todo el vuelo utilizando el mismo combustible que el planificado inicialmente por la compañía. Esta estrategia presenta la ventaja de que los vuelos que están en el aire se encuentran en una situación mas favorable para recuperar parte del retraso que tenían asignado si la regulación se cancela. En primer lugar se ha realizado un estudio de la relación existente entre el combustible usado y el tiempo de vuelo cuando la velocidad de crucero es modificada. A continuación, se ha definido y analizado el retraso que se puede realizar sin repercutir en el consumo en la ausencia y en la presencia de viento. También se ha considerado la influencia de elegir un nivel de vuelo diferente al planificado y el uso de combustible extra para incrementar el retraso. Los resultados muestran que para vuelos de corto y medio alcance, la cantidad de retraso es de en torno a 5 minutos, esta cantidad aumenta a unos 25 minutos para vuelos de largo recorrido. El nivel de vuelo se ha identificado como uno de los parámetros principales que afectan a la cantidad de retraso que puede ser absorbido. Seguidamente se presenta la aplicación de esta técnica en regulaciones de ATFM realistas, y en particular de ground delay programs (GDP). Con el objetivo de mostrar resultados significativos, los GDPs definidos en 2006 en el espacio aéreo norteamericano han sido analizados. Han sido estudiados en detalle escenarios en los aeropuertos de San Francico, Newark y Chicago. Estos tres aeropuertos fueron los aeropuertos que implementaron m´as GDPs en 2006 y por su situación geográfica presentan tráficos con diferentes características. Para considerar el tráfico se han utilizado datos de la Federal Aviation Administration y características aerodinámicas y de consumo provenientes de Airbus. Finalmente, se presenta el efecto de usar radios de exención en los GDPs y el uso de políticas de priorización de vuelos diferentes a la utilizada actualmente (ration-by-schedule). Para concluir se ha realizado una breve discusión sobre el impacto de esta estrategia en la gestión del tráfico aéreo.

This thesis presents a methodology for estimating saturation flow rates at signalized intersections by traffic subgroups. A subgroup is defined as a group of vehicles of a specific vehicle classification that make a single directional movement from one lane. The subgroup method is founded on the procedures described in the 1997 Highway Capacity Manual (HCM) (Transportation Research Board, 1997) but extends beyond the HCM's lane group model to provide results that can be aggregated at multiple levels. Rather than assuming homogeneous conditions within each lane or lane group as is the case with many capacity guides, the subgroup method decomposes a traffic stream into individual components, each of which have unique saturation headways. Comparisons with the HCM show that under similar assumptions, the subgroup method produces similar saturation flow rates when aggregated at the lane group level. This gives confidence for applying the subgroup approach to estimate individual lane performance.The most critical element of the subgroup model is the estimation of lane volumes. Lane volume field data were gathered at four sites. Results of an evaluation of lane distribution strategies for estimating lane volumes when a choice is present indicate that the equal back of queue strategy best reflects driver behavior. Based on the observed field data, the equal back of queue strategy outperforms the equal delay strategy and the equal flow ratio strategy which are widely used in various international capacity guides.

This thesis describes the development of a multi-train simulator in which different train control systems are simulated on a common section of high-speed line operating with four trains. The simulator is used to estimate and compare train knock-on delay performance with different signalling systems. This thesis further demonstrates a train trajectory optimisation work. Four searching approach have been implemented to find, for a specific train, the most appropriate target speed in different areas in order to minimise energy usage and delays. A West Coast Main Line case study is presented in order to assess the operational impact of using optimised train trajectory and different practical train control system configurations combined with three different operating priorities. The result shows that, by using more advanced signalling systems or optimal train trajectories, interactions between trains can be reduced, thereby improving performance. This also has the effect of reducing the energy required to make a particular journey. Simple control systems when coupled with the optimisation process have been shown to have similar performance to the more advanced signalling systems. The use of a dynamic programming allows an objective function to be minimised with the best results and an acceptable computation time.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.
Includes bibliographical references (leaves 42-43).
We formulate a model for planning the rerouting of aircraft to alleviate en-route congestion, with system capacity being modeled stochastically. To overcome problems with tractability, we apply a Dantzig-Wolfe decomposition and present an efficient method for solving it. The decomposed formulation is shown to be tractable for real-world problem, and it generates up to a ten percent reduction in cost when compared to an otherwise equivalent deterministic model. We show that even when the decomposed formulation fails to terminate within a reasonable time, a near-optimal solution can still be generated.
by Joshua B. Marron.
M.Eng.

Cities around the globe try to alleviate congested traffic, especially in economically fast growing cities. In order to help maintain this economic growth, cities must make alleviating congested traffic a priority. The purpose of this paper is to study the traffic problem in Riyadh city in Saudi Arabia and propose a solution. This paper will begin with a brief background about the city and then explain the problem. Afterward, the requirements of the new system will be discussed. Next, using analysis of alternatives, different solutions will be explored and through trade study, some of those alternatives will be chosen to be a part of the new system. Systems Architecture will be used to help readers visualize the current and future systems and in the modeling section, the results of a survey regarding the traffic problem in Riyadh are taken into consideration. This will be combined with a discussion on queuing and forecasting methods. The project is looked at from a Lean point of view to try and minimize waste within traffic administrations by suggesting a new organizational chart. Finally, ethics and risk managements are discussed. The goal of the document is to explore the traffic problem in Riyadh in hopes of finding a solution.

Automatically calculating periodic timetables in public railway transport systems is an NP-complete problem – namely the Periodic Event Scheduling Problem (PESP). The original model is restricted to basic periodic timetabling. Extending the model by decisional transport networks with flows induces new possibilities in the timetabling and planning process. Subsequently, the given flexibility results in a generic model extension of PESP that can be applied in subsets of the timetabling process. The successful utilization of this approach is presented for distinct chain paths, duplicated chain paths and non-connected flow graphs that represent integration of routing and timetabling, planning of periodic rail freight train paths and track allocation, respectively. Furthermore, the encoding of this generic model into a binary propositional formula is introduced and the appropriate usage of several techniques like SAT solving and MaxSAT to calculate and optimize the corresponding instances will be presented accordingly. Computational results for real-world scenarios suggest the practical impact and give promising perspectives for further scientific research.

This paper explores the potential applications of existing spectral clustering algorithms to real life problems through experiments on existing road traffic data. The analysis begins with an overview of previous unsupervised machine learning techniques and constructs an effective spectral clustering algorithm that demonstrates the analytical power of the method. The paper focuses on the spectral embedding method’s ability to project non-linearly separable, high dimensional data into a more manageable space that allows for accurate clustering. The key step in this method involves solving a normalized eigenvector problem in order to construct an optimal representation of the original data. While this step greatly enhances our ability to analyze the relationships between data points and identify the natural clusters within the original dataset, it is difficult to comprehend the eigenvalue representation of the data in terms of the original input variables. The later sections of this paper will explore how the careful framing of questions with respect to available data can help researchers extract tangible decision driving results from real world data through spectral clustering analysis.

Area-based (i.e., non-lane based) heterogeneous traffic (as in developing countries) differs significantly from lane-based homogeneous traffic (as in developed countries). In area-based traffic, drivers generally ignore the lane markings and perceive the entire road space while progressing longitudinally. Traditional car-following and lane-changing models are not directly applicable to modelling such driving behaviour. This research aimed to microscopically model the dynamic of the subject vehicle in area-based traffic flow. The modelling was conducted in two steps. In Step 1, discrete choice-based modelling was conducted to identify the area-based movement direction of the subject vehicle. In Step 2, a vehicle-following behaviour model was developed to simulate the next position of the subject vehicle (along the direction of a selected alternative, as modelled in Step 1 of this modelling). The macroscopic validation of the model was performed to ensure the robustness of the model.

This PhD thesis is concerned with applications of nonlinear systems of conservation laws to gas dynamics and traffic flow modeling. The first part is devoted to the analytical description of a fluid flowing in a tube with varying cross section. We study the 2x2 model of the p-system and than, we extend the properties to the full 3x3 Euler system. We also consider a general nxn strictly hyperbolic system of balance laws; we study the Cauchy problem for this system and we apply this result to the fluid flow in a pipe wiyh varying section. Concerning traffic flow, we introduce a new macroscopic model, based on a non-smooth 2x2 system of conservation laws. We study the Riemann problem for this system and the qualitative properties of its solutions that are relevant from the point of view of traffic.

Thesis (M.S.)--University of Missouri-Columbia, 2005.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (July 11, 2006) Includes bibliographical references.