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Dissertations / Theses on the topic 'Traffic flow modelling'
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1
Zhang, Jin. "Probabilistic modelling for flow density relationship." Thesis, Griffith University, 2018. http://hdl.handle.net/10072/378750.
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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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2
Silva, Paulo Cesar Marques. "Modelling interactions between bus operations and traffic flow." Thesis, University College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367562.
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Sarkar, Nikhil Chandra. "Microscopic modelling of the area-based traffic flow." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/129869/9/Nikhil%20Chandra%20Sarkar%20Thesis.pdf.
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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.
4
Mongeot, Helene. "Traffic incident modelling in mixed urban networks." Thesis, University of Southampton, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286751.
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Lu, Kang Hsin. "Modelling of saturated traffic flow using highly parallel systems." Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245726.
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Cowburn, G. J. "Bayesian mixture modelling with application to road traffic flow." Thesis, University of Sunderland, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269160.
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Fitzgerald, Aidan. "Hybrid macroscopic modelling of vehicular traffic flow in road networks." Thesis, Queen's University Belfast, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680154.
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Macroscopic modelling of road traffic flow is far from complete, different models exhibit strengths when used in varying situations. Continuum models, based on fluid dynamics are accurate and robust in describing traffic on a single road. Knowledge-based models, derived from heuristics based on either statistical methods or Artificial Intelligence techniques and are efficient at describing traffic processes at intersections. Neither of the existing approaches is separately able to capture effectively traffic dynamics in road networks. The thesis Introduces a hybrid macroscopic approach, combining continuum methods and knowledge-based models. It Is implemented using three different forecasting methods, namely neural network, random walk and SARIMA models each coupled with the Lighthill-Whitham and Richards continuum model. Results from numerical experiments confirm the promising features of the introduced approach in describing effectively traffic dynamics in road networks. The developed models are theoretically rigorous, numerically reliable, computationally efficient and suitable for real world applications.
8
Wright, Benjamin John. "A Bayesian dynamic approach to modelling flow through a traffic network." Thesis, Open University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430591.
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Bedjaoui, Nabil, Joaquim Correia, Sackmone Sirisack, and Bouasy Doungsavanh. "Traffic Modelling and Some Inequalities in Banach Spaces." Master's thesis, Edited by Thepsavanh Kitignavong, Faculty of Natural Sciences, National University of Laos, 2017. http://hdl.handle.net/10174/26575.
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Modelling traffic flow has been around since the appearance of traffic jams. Ideally, if we can
correctly predict the behavior of vehicle flow given an initial set of data, then adjusting the
flow in crucial areas can maximize the overall throughput of traffic along a stretch of road.
We consider a mathematical model for traffic flow on single land and without exits or entries. So, we are just observing what happens as time evolves if we fix at initial time (t = 0) some special distribution of cars (initial datum u_0). Because we do approximations, we need the notion of convergence and its corresponding topology. The numerical approximation of scalar conservation laws is carried out by using conservative methods such as the Lax-Friedrichs and the Lax-Wendroff schemes.
The Lax-Friedrichs scheme gives regular numerical solutions even when the exact solution is discontinuous (shock waves). We say the scheme is diffusive meaning that the scheme is solving in fact an evolution equation of the form u_t+f(u)_x = epsilon u_xx, where epsilon is a small parameter depending on ∆x and ∆t.
The Lax-Wendroff scheme is more precise than the Lax-Friedrichs scheme, and give the right position of the discontinuities for the shock waves. But it develop oscillations. We say the scheme is dispersive what means the scheme is solving approximatively an evolution equation of the form u_t + f(u)_x = delta u_xxx, where delta is a small parameter depending on ∆x and ∆t.
An elaboration and an implementation of Lax-Friedrichs schemes and of Lax-Wendroff schemes even extended to second order provided numerical solutions to the problem of traffic flows on the road. Since along the roads the schemes present the same features as for conservation laws, the new and original aspect is given by the treatment of the solution at junctions.
Our tests show the effectiveness of the approximations, revealing that Lax-Wendroff schemes is more accurate than Lax-Friedrichs schemes.
10
Yaiaroon, Niphan. "Probabilistic modelling of extreme traffic load-effects based on WIM data." Thesis, The University of Sydney, 2009. https://hdl.handle.net/2123/28224.
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The primary aims of this thesis are to develop a realistic probabilistic model of extreme
traffic load-effects (referred to as a Probabilistic Model), which could be used for a
reliability—based assessment of the safety of existing bridges, and to develop a model
that provides an efficient approximation (without significant computational difficulties)
for the Probabilistic Model (referred to as an Approximate Model). The research
focuses on the analysis of traffic load-effects estimated from Weigh-in-Motion data by
calculating hypothetical load-effects that would be induced by each vehicle.
Considerations are given to single-span simply—supported and typical three—span
continuous bridges with main span lengths up to 40 m, and the load—effect results are
used as the basis for calibrating realistic probabilistic models proposed in this research.
A preliminary assessment scheme is developed to determine the quality of WIM
data, including a rational method to assist in accepting or rejecting daily data records. A
key feature is to inspect the data for consistency of the average daily single steer axle
mass distributions for selected vehicle patterns. Visual inspection of graphs of statistical
distributions is also essential for WIM data with significant temporal variations. The
site-specific traffic characteristics for each WIM site that can be derived from the
obtained WIM data are examined and presented.
A simulation study on theoretical static peak load-effects given by the obtained
WIM data was conducted in order to analyse frequency distributions of normalised peak
load-effects, normalised with respect to ‘characteristic values’. For peak load—effects
normalised with respect to the corresponding 99th percentile peak load-effects (as
characteristic values), it was found in general that the extreme normalised peak loadeffect
distributions (exceeding the load-effect thresholds) were essentially the same for
all load-effects. The peak load-effects normalised with respect to the corresponding
peak load-effects given by the T44 design load were also examined and it was found
that the T44 design load did not provide a good representation of the critical vehicles for
the traffic loads considered.
A Probabilistic Model that can be used effectively to approximate all
distributions of extreme normalised peak load-effects is developed to describe the
distributions given by general vehicles. The Probabilistic Models include an upper limit
on the maximum load-effect, and the models were validated by comparing with the
distributions of theoretical load-effects obtained from the WIM data. Furthermore, for
selected cases, they were also compared with extrapolations of extreme normalised peak
load—effects based on approximate Normal probability distributions. The resultant
distributions show that the Probabilistic Models provide an efficient basis to
approximately describe the distributions for WIM data without a large proportion of
heavily overloaded C10 (1-2-2-2) vehicles.
An example is provided for a case in which the extreme normalised peak loadeffect
distribution is not accurately described by a Normal probability distribution,
whereas sufficient accuracy is provided by a Probabilistic Model calibrated specifically
for this load-effect distribution. Extreme value distributions corresponding to sample
sizes of 1 million and 100 million vehicles were derived from the Probabilistic Models
and the Normal probability approximations for selected cases, and differences between
these extreme value distributions were inspected to study the effect of the upper limits
of the Probabilistic Models.
Finally, validation of the Approximate Models was carried out for selected cases
by comparing with the Probabilistic Models and the distributions obtained from WIM
data. An approximate threshold value for the Approximate Model is given by a
characteristic truck model capable of predicting the threshold values for all load-effects.
This truck model is based simply on the GVM information fiom the WIM data.
Satisfactory results were obtained from the characteristic truck model for describing
threshold values for all bridge types and all load-effects, using a very simple method,
and the threshold value estimation was most accurate for bridges with long main span
lengths.
The accuracy of the Approximate Model depends on the accuracy of the
characteristic truck model to estimate the threshold values. For selected cases, it has
been found that the Approximate Models provide an efficient and reasonably accurate
basis to approximate the distributions obtained from WIM data and the detailed
Probabilistic Models developed in this research.
11
Sutomo, Heru. "Appropriate saturation flow at traffic signals in Javanese cities : a modelling approach." Thesis, University of Leeds, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305681.
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Cassir, C. "A flow model for the analysis of transport network reliability." Thesis, University of Newcastle Upon Tyne, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364764.
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Mohammadian, Saeed. "Freeway traffic flow dynamics and safety: A behavioural continuum framework." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/227209/1/Saeed_Mohammadian_Thesis.pdf.
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Congestion and rear-end crashes are two undesirable phenomena of freeway traffic flows, which are interrelated and highly affected by human psychological factors. Since congestion is an everyday problem, and crashes are rare events, congestion management and crash risk prevention strategies are often implemented through separate research directions. However, overwhelming evidence has underscored the inter-relation between rear-end crashes and freeway traffic flow dynamics in recent decades. This dissertation develops novel mathematical models for freeway traffic flow dynamics and safety to integrate them into a unifiable framework. The outcomes of this PhD can enable moving towards faster and safer roads.
14
Ismail, Emad Abbas. "Highway intersections with alternative priority rules." Thesis, University of Bradford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277143.
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Kako, Soichiro. "Microscopic modelling of merging at unsignalised intersections and its application to freeway merging." Thesis, Queensland University of Technology, 1998.
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16
Fan, Shimao. "Data-Fitted Generic Second Order Macroscopic Traffic Flow Models." Diss., Temple University Libraries, 2013. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/233877.
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MathematicsPh.D.
The Aw-Rascle-Zhang (ARZ) model has become a favorable ``second order" macroscopic traffic model, which corrects several shortcomings of the Payne-Whitham (PW) model. The ARZ model possesses a family of flow rate versus density (FD) curves, rather than a single one as in the ``first order" Lighthill-Whitham-Richards (LWR) model. This is more realistic especially during congested traffic state, where the historic fundamental diagram data points are observed to be set-valued. However, the ARZ model also possesses some obvious shortcomings, e.g., it assumes multiple maximum traffic densities which should be a ``property" of road. Instead, we propose a Generalized ARZ (GARZ) model under the generic framework of ``second order" macroscopic models to overcome the drawbacks of the ARZ model. A systematic approach is presented to design generic ``second order" models from historic data, e.g., we construct a family of flow rate curves by fitting with data. Based on the GARZ model, we then propose a phase-transition-like model that allows the flow rate curves to coincide in the free flow regime. The resulting model is called Collapsed GARZ (CGARZ) model. The CGARZ model keeps the flavor of phase transition models in the sense that it assume a single FD function in the free-flow phase. However, one should note that there is no real phase transition in the CGARZ model. To investigate to which extent the new generic ``second order" models (GARZ, CGARZ) improve the prediction accuracy of macroscopic models, we perform a comparison of the proposed models with two types of LWR models and their ``second order" generalizations, given by the ARZ model, via a three-detector problem test. In this test framework, the initial and boundary conditions are derived from real traffic data. In terms of using historic traffic data, a statistical technique, the so-called kernel density estimation, is applied to obtain density and velocity distributions from trajectory data, and a cubic interpolation is employed to formulate boundary condition from single-loop sensor data. Moreover, a relaxation term is added to the momentum equation of selected ``second order" models to address further unrealistic aspects of homogeneous models. Using these inhomogeneous ``second order" models, we study which choices of the relaxation term &tau are realistic.
Temple University--Theses
17
Tampère, Chris M. J. "Human-kinetic multiclass traffic flow theory and modelling. With application to Advanced Driver Assistance Systems in congestion." Diss., Delft University of Technology, 2004. http://hdl.handle.net/10919/71567.
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Motivated by the desire to explore future traffic flows that will consist of a mixture of classical vehicles and vehicles equipped with advanced driver assistance systems, new mathematical theories and models are developed. The basis for this theory was borrowed from the kinetic description of gas flows, where we replaced the behaviour of the molecules by typical human driving behaviour. From a methodological point of view, this 'human-kinetic' traffic flow theory provides two major improvements with respect to existing theory. Firstly, the model builds exclusively on a mathematical description of individual driver behaviour, whereas traditionally field measurements of traffic flow variables like flow rate and average speed of the flow are needed. This is of major importance for the exploration of future traffic flows with vehicles and equipment that are not yet on the market, and for which at best individual test results from driving simulator experiments or small scale field trials are available. Secondly, the model accounts for the more refined aspects of individual driver behaviour by considering the 'internal' state of the driver (active/passive, aware/unaware,...) and the variations of driving strategy that occur during driving. This is important when the ambition is to capture refined congestion patterns like the occurrence of stop-and-go waves, oscillating congestion and long jams, where the driving strategy may depend for instance on the motivation of the driver to follow closely. This new theory links together the worlds of traffic engineers and behavioural scientists. As such, it is a promising tool that increases the insight in the human behaviour as a basis of various dynamic congestion patterns, and it facilitates the design and evaluation of electronic systems in the vehicle that assist the driver to behave safer, more comfortable and more efficient in busy traffic flows. Herewith, the results of this research are relevant, both for the theoretical interest of the TRAIL research school, and for the more practically oriented work of TNO, who provided financing for this research in the joint T3 research program.
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Neubert, Lutz. "Statistische Analyse von Verkehrsdaten und die Modellierung von Verkehrsfluss mittels zellularer Automaten - Statistical Analysis of Traffic Data and Modelling of Traffic Flow using Cellular Automata." Gerhard-Mercator-Universitaet Duisburg, 2001. http://www.ub.uni-duisburg.de/ETD-db/theses/available/duett-05222001-113330/.
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Past and recent investigations of traffic dynamics mostly rest on averaged data taken over a short period of time, e.g. one minute. They make a qualitative distinction between the generally accepted traffic states called "free flow", "synchronised flow" and "Stop-and-Go traffic" possible. However, the essential car-car-interactions on the microscopic level are concealed. With extensive statistical examinations of single-vehicle traffic data presented in this work one gains new insights especially from a microscopic point of view. By means of time series analyses, correlation functions and by use of histogram methods new evaluation methods for driving behaviour are introduced. These quantities show a strong dependency on the present traffic state, the observed interval of density and the environment (e.g., freeway or city traffic). Microscopic features like synchronisation of velocities ranging over a number of vehicles or decreasing time headways smaller than one second noticeably influence macroscopic proper ties of traffic as expressed in fundamental diagrams. Moreover, on the basis of cross correlation functions connecting flow and density some quantities can be defined to discriminate between the several traffic states quantitatively. These empirical results have impacts on modelling and simulation of traffic flow. A modified cellular automaton comprising aspects of anticipation is introduced and discussed in great detail. Metastable states can be formed and all other criteria are also met to indicate a well-operating traffic flow model. A lot of simulations were done in order to analyse single-lane and multi-lane behaviour and to find out the specific problems coming along with event-driven measuremens methods using "inductive loops". Another focus are density waves to estimate their speed and to elucidate the phase separation and the transition between different traffic states.
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Mohorcic, M., A. Svigelj, G. Kandus, Yim Fun Hu, and Ray E. Sheriff. "Demographically weighted traffic flow models for adaptive routing in packet-switched non-geostationary satellite meshed networks." Elsevier, 2003. http://hdl.handle.net/10454/4176.
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noIn this paper, a performance analysis of adaptive routing is presented for packet-switched inter-satellite link (ISL)networks, based on shortest path routing and two alternate link routing forwarding policies. The selected routing algorithm and link-cost function are evaluated for a low earth orbit satellite system, using a demographically weighted traffic flow model. Two distinct traffic flow patterns are modelled: hot spot and regional. Performance analysis, in terms of quality of service and quantity of service, is derived using specifically developed simulation software to model the ISL network, taking into account topology adaptive routing only, or topology and traffic adaptive routing.
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Danielsson, Anna, and Gabriella Gustafsson. "Link flow destination distribution estimation based on observed travel times for traffic prediction during incidents." Thesis, Linköpings universitet, Kommunikations- och transportsystem, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-170080.
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In a lot of big cities, the traffic network is overloaded, with congestion and unnecessary emissions as consequence. Therefore, different traffic control methods are useful, especially in case of an incident. One key problem for traffic control is traffic prediction and the aim of this thesis is to develop, calibrate and evaluate a route flow model using only observed travel times and travel demand as input. The route flow model was used to calculate the metric link flow destination distribution, that presents to which destinations the travelers on a link are going in percentage.
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Patterson, Joanne Louise. "Urban scale modelling of traffic and cycling flow using spatial analysis and an assessment of factors that influence cyclist behaviour." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/66970/.
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To understand and facilitate modal shift to more sustainable modes of transport there is a need to model accessibility and connectivity at an urban scale using data collection and modelling procedures that require less data and specialist input than traditional transport models. This research has used spatial analysis modelling procedures based on space syntax to investigate the potential to model aggregate traffic flows at an urban scale, and to investigate the potential to apply the same methodology to model both aggregate and individual cycle flows. Cyclist behaviour has been investigated through a questionnaire to support modelling work. The research has demonstrated that spatial analysis modelling is an effective means of representing urban scale motor traffic network, however, modifications to the model were required to achieve a correlation between modelled and measured motor traffic flow comparable to other modelling procedures. Boundary weighting was found to be effective at representing traffic crossing the boundary of an isolated urban sub-area, but was not so effective at an urban scale. Road weighting was found to be effective in improving model performance by representing traffic flows along routes according to a national classification scheme. It was demonstrated that these modelling principles could be used to represent an urban bicycle network and that the impact of the modification of infrastructure on relative flows of both cyclists and motor traffic could be accommodated. The modelling approach has the potential to be extremely useful at an early planning stage to represent changes to flows across the network. A survey of behaviour identified that cyclists modify their journey to use cycling facilities such as on-road lanes and off-road paths, or to avoid particular areas perceived to be less favourable for cyclists and that analysis indicates that it is difficult to predict (25% from survey) individual route choice. Results indicate that there were more opportunities related to route characteristics that could be influenced by infrastructure changes for occasional cyclists than for frequent/everyday cyclists.
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Sederlin, Michael. "Traffic State Estimation for Signalized Intersections : A Combined Gaussian Process Bayesian Filter Approach." Thesis, KTH, Transportplanering, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-284198.
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Traffic State Estimation (TSE) is a vital component in traffic control which requires an accurate viewof the current traffic situation. Since there is no full sensor coverage and the collected measurementsare inflicted with random noise, statistical estimation techniques are necessary to accomplish this.Common methods, which have been used in highway applications for several decades, are state-spacemodels in the form of Kalman Filters and Particle Filters. These methods are forms of BayesianFilters, and rely on transition models to describe the system dynamics, and observation models torelate collected measurements to the current state. Reliable estimation of traffic in urban environmentshas been considered more difficult than in highways owing to the increased complexity.This MsC thesis build upon previous research studying the use of non-parametric Gaussian Processtransition and measurement models in an extended Kalman Filter to achieve short-term TSE. To dothis, models requiring different feature sets are developed and analysed, as well as a hybrid approchcombining non-parametric and parametric models through an analytical mean function based on vehicleconservation law. The data used to train and test the models was collected in a simulated signalizedintersection constructed in SUMO.The presented results show that the proposed method has potential to performing short-term TSE inthis context. A strength in the proposed framework comes from the probabilistic nature of the GaussianProcesses, as it removes the need to manually calibrate the filter parameters of the Kalman Filter. Themean absolute error (MAE) lies between one and five vehicles for estimation of a one hour long dataseries with varying traffic demand. More importantly, the method has desirable characteristics andcaptures short-term fluctuations as well as larger scale demand changes better than a previously proposedmodel using the same underlying framework. In the cases with poorer performance, the methodprovided estimates unrelated to the system dynamics as well as large error bounds. While the causefor this was not determined, several hypotheses are presented and analysed. These results are takento imply that the combination of BF and GP models has potential for short-term TSE in a signalizedintersection, but that more work is necessary to provide reliable algorithms with known bounds. In particular,the relative ease of augmenting an available analytical model, built on conventional knowledgein traffic modelling, with a non-parametric GP is highlighted.
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Bevrani, Bayan. "Multi-criteria capacity assessment and planning models for multi-modal transportation systems." Thesis, Queensland University of Technology, 2018. https://eprints.qut.edu.au/122895/1/Bayan_Bevrani_Thesis.pdf.
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This research provides a comprehensive set of methods for the capacity assessment of multi-modal transportation systems, which are easy to apply and can significantly reduce the time to perform a capacity analysis. This thesis developed multi-objective mathematical models that can evaluate the effect of parametric and structural changes and can assist planners to update and reconfigure multi-modal transportation systems considering the trade-off in different aspects of cost, time and functionality. The methods proposed in this thesis can help planners and decision-makers to identify the performance and capability of multiple modes of an integrated transportation system.
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Peterson, Anders. "The Origin-Destination Matrix Estimation Problem : Analysis and Computations." Doctoral thesis, Norrköping : Dept. of Science and Technology, Linköpings universitet, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8859.
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Mercier, Magali. "Étude de différents aspects des EDP hyperboliques : persistance d’onde de choc dans la dynamique des fluides compressibles, modélisation du trafic routier, stabilité des lois de conservation scalaires." Thesis, Lyon 1, 2009. http://www.theses.fr/2009LYO10246/document.
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On étudie dans ce travail des systèmes de lois de conservation hyperboliques. La première partie étudie le temps d'existence des solutions régulières et régulières par morceaux de la dynamique des fluides compressibles. Après avoir présenté l'état de l'art en matière de solutions régulières, on montre une extension d'un théorème de Grassin à des gaz de Van der Waals. On étudie ensuite les solutions ondes de chocs : on poursuit l'approche de T. T. Li pour estimer leur temps d'existence dans le cas isentropique à symétrie sphérique, et l'approche de Whitham afin d'obtenir une équation approchée vérifiée par la surface de discontinuité. Dans une deuxième partie, motivée par la modélisation d'un rond-point en trafic routier, on étudie une extension multi-classe du modèle macroscopique de Lighthill-Whitham-Richards sur une route infinie avec des jonctions. On différencie les véhicules selon leur origine et leur destination et on introduit des conditions aux bords adaptées au niveau des jonctions. On obtient existence et unicité d'une solution au problème de Riemann pour ce modèle. Des simulations numériques attestent que les solutions obtenues existent en temps long. On aborde enfin le problème de Cauchy par la méthode de front tracking. La dernière partie concerne les lois de conservation scalaires. La première question abordée est le contrôle de la variation totale de la solution et la stabilité des solutions faibles entropiques par rapport au flux et à la source. Ce résultat nous permet d'étudier des équations avec flux non-local. Une fois établi leur caractère bien posé, on montre la Gâteaux-différentiabilité du semi-groupe obtenu par rapport aux conditions initialesIn this work, we study hyperbolic systems of balance laws. The first part is devoted to compressible fluid dynamics, and particularly to the lifespan of smooth or piecewise smooth solutions. After presenting the state of art, we show an extension to more general gases of a theorem by Grassin.We also study shock waves solutions: first, we extend T. T. Li's approach to estimate the time of existence in the isentropic spherical case; second, we develop Whitham's ideas to obtain an approximated equation satisfied by the discontinuity surface. In the second part, we set up a new model for a roundabout. This leads us to study a multi-class extension of the macroscopic Lighthill-Whitham-Richards' model. We study the traffic on an infinite road, with some points of junction. We distinguish vehicles according to their origin and destination and add some boundary conditions at the junctions. We obtain existence and uniqueness of a weak entropy solution for the Riemann problem. As a complement, we provide numerical simulations that exhibit solutions with a long time of existence. Finally, the Cauchy problem is tackled by the front tracking method. In the last part, we are interested in scalar hyperbolic balance laws. The first question addressed is the control of the total variation and the stability of entropy solutions with respect to flow and source. With this result, we can study equations with non-local flow, which do not fit into the framework of classical theorems. We show here that these kinds of equations are well posed and we show the Gâteaux-differentiability with respect to initial conditions, which is important to characterize maxima or minima of a given cost functional
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Hu, Jia. "Analysis and improvement of medium access control protocols in wireless networks : performance modelling and Quality-of-Service enhancement of IEEE 802.11e MAC in wireless local area networks under heterogeneous multimedia traffic." Thesis, University of Bradford, 2010. http://hdl.handle.net/10454/4466.
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In order to efficiently utilize the scarce wireless resource as well as keep up with the ever-increasing demand for Quality-of-Service (QoS) of multimedia applications, wireless networks are undergoing rapid development and dramatic changes in the underlying technologies and protocols. The Medium Access Control (MAC) protocol, which coordinates the channel access and data transmission of wireless stations, plays a pivotal role in wireless networks. Performance modelling and analysis has been and continues to be of great theoretical and practical importance in the design and development of wireless networks. This research is devoted to developing efficient and cost-effective analytical tools for the performance analysis and enhancement of MAC protocols in Wireless Local Area Networks (WLANs) under heterogeneous multimedia traffic. To support the MAC-layer QoS in WLANs, the IEEE 802.11e Enhanced Distributed Channel Access (EDCA) protocol has proposed three QoS differentiation schemes in terms of Arbitrary Inter-Frame Space (AIFS), Contention Window (CW), and Transmission Opportunity (TXOP). This research starts with the development of new analytical models for the TXOP scheme specified in the EDCA protocol under Poisson traffic. A dynamic TXOP scheme is then proposed to adjust the TXOP limits according to the status of the transmission queue. Theoretical analysis and simulation experiments show that the proposed dynamic scheme largely improves the performance of TXOP. To evaluate the TXOP scheme in the presence of ii heterogeneous traffic, a versatile analytical model is developed to capture the traffic heterogeneity and model the features of burst transmission. The performance results highlight the importance of taking into account the heterogeneous traffic for the accurate evaluation of the TXOP scheme in wireless multimedia networks. To obtain a thorough and deep understanding of the performance attributes of the EDCA protocol, a comprehensive analytical model is then proposed to accommodate the integration of the three QoS schemes of EDCA in terms of AIFS, CW, and TXOP under Poisson traffic. The performance results show that the TXOP scheme can not only support service differentiation but also improve the network performance, whereas the AIFS and CW schemes provide QoS differentiation only. Moreover, the results demonstrate that the MAC buffer size has considerable impact on the QoS performance of EDCA under Poisson traffic. To investigate the performance of EDCA in wireless multimedia networks, an analytical model is further developed for EDCA under heterogeneous traffic. The performance results demonstrate the significant effects of heterogeneous traffic on the total delay and frame losses of EDCA with different buffer sizes. Finally, an efficient admission control scheme is presented for the IEEE 802.11e WLANs based on analytical modelling and a game-theoretical approach. The admission control scheme can maintain the system operation at an optimal point where the utility of the Access Point (AP) is maximized with the QoS constraints of various users.
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Johnson, Lynne Alison. "Modelling particle emissions from traffic flows." Thesis, Queensland University of Technology, 2000.
Find full text
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Mouchos, Charalampos. "Traffic and performance evaluation for optical networks : an investigation into modelling and characterisation of traffic flows and performance analysis and engineering for optical network architectures." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4265.
Full textAbstract:
The convergence of multiservice heterogeneous networks and ever increasing Internet applications, like peer to peer networking and the increased number of users and services, demand a more efficient bandwidth allocation in optical networks. In this context, new architectures and protocols are needed in conjuction with cost effective quantitative methodologies in order to provide an insight into the performance aspects of the next and future generation Internets. This thesis reports an investigation, based on efficient simulation methodologies, in order to assess existing high performance algorithms and to propose new ones. The analysis of the traffic characteristics of an OC-192 link (9953.28 Mbps) is initially conducted, a requirement due to the discovery of self-similar long-range dependent properties in network traffic, and the suitability of the GE distribution for modelling interarrival times of bursty traffic in short time scales is presented. Consequently, using a heuristic approach, the self-similar properties of the GE/G/∞ are being presented, providing a method to generate self-similar traffic that takes into consideration burstiness in small time scales. A description of the state of the art in optical networking providing a deeper insight into the current technologies, protocols and architectures in the field, which creates the motivation for more research into the promising switching technique of 'Optical Burst Switching' (OBS). An investigation into the performance impact of various burst assembly strategies on an OBS edge node's mean buffer length is conducted. Realistic traffic characteristics are considered based on the analysis of the OC-192 backbone traffic traces. In addition the effect of burstiness in the small time scales on mean assembly time and burst size distribution is investigated. A new Dynamic OBS Offset Allocation Protocol is devised and favourable comparisons are carried out between the proposed OBS protocol and the Just Enough Time (JET) protocol, in terms of mean queue length, blocking and throughput. Finally the research focuses on simulation methodologies employed throughout the thesis using the Graphics Processing Unit (GPU) on a commercial NVidia GeForce 8800 GTX, which was initially designed for gaming computers. Parallel generators of Optical Bursts are implemented and simulated in 'Compute Unified Device Architecture' (CUDA) and compared with simulations run on general-purpose CPU proving the GPU to be a cost-effective platform which can significantly speed-up calculations in order to make simulations of more complex and demanding networks easier to develop.
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Salvi, Francesco. "Effetti di congestione per modelli di traffico su rete stradale: uno studio su Bologna." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23734/.
Full textAbstract:
Nell'ultimo decennio, un notevole interesse nell'ambito della modellizzazione del traffico si è sviluppato attorno al concetto dei Diagrammi Fondamentali Macroscopici (MFD), resi popolari da un celebre esperimento condotto nel 2008 nella città giapponese di Yokohama. Tali diagrammi mettono in relazione le medie spaziali di flusso, densità e velocità su un intero network stradale e risultano sotto certe condizioni una proprietà intrinseca di quest'ultimo, indipendente dalla domanda di mobilità degli utenti, costituendo così potenzialmente un importante strumento nel controllo dinamico del traffico. Il presente lavoro si propone quindi di indagare l'esistenza di MFD in un network extraurbano attorno alla città di Bologna, composto sia da tratti di autostrada e tangenziale che da strade statali e provinciali. I diagrammi sono stati costruiti utilizzando una simulazione di traffico sulla regione Emilia-Romagna, basata su un input di dati di mobilità provenienti da utenti della rete TIM che consentono di ricavare su base oraria gli spostamenti aggregati dei veicoli. Se il carico è sufficientemente alto, si osserva negli MFD l'emergere di fenomeni di isteresi, a causa dei quali si trovano a parità di densità media valori differenti di flusso e velocità. Le cause dell'isteresi sono quindi analizzate nel dettaglio studiando gli effetti della congestione sulla variabilità spaziale della densità, che risulta essere un fattore chiave insieme all'eterogeneità della rete nella forma dei diagrammi.
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N, Arumuga Subhashini. "Modelling traffic flow on interchange." Thesis, 2014. http://ethesis.nitrkl.ac.in/6304/1/E-62.pdf.
Full textAbstract:
The rapid urbanization alters the life style in high scale and metropolitan cities adapt traffic diverting structures like interchanges and bridges to handle the ever increasing traffic growth. It is high time to effectively utilize these traffic systems, hence a traffic model explaining the effective travel pattern is obligatory. Fuzzy logic is an effective concept in interpreting and reciprocating performance similar to human reasoning and can describe complex systems in linguistic terms instead of numerical values. In this thesis, a system was established based on Fuzzy Inference System (FIS) with output data as Vehicular Speed (S) and input data as various highway geometric elements. The study was conducted on two steps as for up - ramp condition and down – ramp condition. Two Traffic models (TFup & TFdn) were developed with radius of curvature, super elevation, frictional coefficient and slope as governing factors. The inferences show that these models can be used to predict and understand the traffic flow along the interchanges with the effect of gravity and friction on the travelling vehicle. A correlation was established between the geometric elements and speed of the vehicle. A simulation study and real life data analysis were performed to demonstrate model fitting the performances of the proposed model.
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Stang, Norman Erik. "Modelling the driver for traffic flow simulation." Thesis, 1993. http://hdl.handle.net/2429/1472.
Full textAbstract:
For 60 years, engineers have modelled traffic flow for use in roadway analysis and design. A continuing problem with such models, though, is their inability to adequately capture the human element in the system. The human driver does not think and act in precise ways, making him difficult to model using conventional mathematical means. This research explored an alternative method of formulating driving models. It started from a psychological basis and used fuzzy logic. Fuzzy logic provided a systematic way of handling imprecision, and its constructs allowed a more intuitive model of driving, one more closely resembling the thinking and acting patterns of humans. A new fuzzy logic driver model was developed. Its structure was based on a general psychological model of human information processing. It was designed so it could be programmed with specific driving behaviour by an end user. To demonstrate and validate it, the model was programmed for two lane rural highway driving and used in simulations of these facilities. Results were compared to field data and the Highway Capacity Manual and proved favourable. The result of the work was a computer based road simulation toolbox containing the new fuzzy logic driver model. The toolbox provides a user with the ability to construct his own road networks, driver types, and vehicle types. With these, he can simulate traffic and examine both isolated incidents and overall performance measures.
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Mayakuntla, Sai Kiran. "Macroscopic modelling of heterogeneous, disordered road traffic flow." Thesis, 2019. https://etd.iisc.ac.in/handle/2005/4466.
Full textAbstract:
The groundwork for much of the existing traffic flow theory was laid in the 1950s and 1960s by researchers from developed economies like the United States. The car-following modelling approach, which is arguably the most popular type of microscopic traffic flow models, and the kinematic wave modelling approach, which is still the basis for much of the macroscopic traffic flow theory, were first introduced during this period. Because the object of this and much of the subsequent research it has spawned is the traffic of developed economies, the classical traffic flow theory deals almost exclusively with this specific kind of traffic: lane-disciplined with relatively homogeneous passenger car traffic. However, the traffic in many developing economies have a significant share of two and three-wheeler motorized vehicles and non-motorized vehicles with different static and dynamic characteristics, resulting in a fundamentally different traffic stream. Because of the differences in sizes and manoeuvrabilities, the vehicles in this traffic stream do not follow the lane-discipline. This kind of traffic has been described in the literature as “heterogeneous, disordered (HD)” or “mixed” traffic.
These developing economies, mostly from Asia and Africa, are rapidly urbanizing and the need to deal with the challenge of traffic congestion is more urgent than ever. Given that these countries are already struggling to keep pace with the rising urban population for providing the necessary road infrastructure, it may be more effective to make the most efficient use of the existing infrastructure through the use of traffic management solutions like real-time traffic monitoring and signal control. As such solutions cannot be formulated using the traditional traffic flow theory, an alternative theory that explicitly considers the characteristics of the HD traffic is urgently needed.
In the present study, HD traffic is characterised by the division of its component vehicle classes into car-following and gap-filling types. Flow-density relationships are derived for each vehicle type based on first principles. A new multiclass cell transmission model (CTM) is then proposed that can accommodate these vehicle classes of these two types, and its properties are analysed. This is followed by the development of a new node-based dynamic traffic assignment (DTA) framework embedded with a single class CTM satisfying the link-level first-in-first-out principle. Both the dynamic user equilibrium (DUE) and dynamic system optimum (DSO) problems are formulated within this framework as complementarity problems with guaranteed solution existence. Algorithms are developed to efficiently compute all the relevant travel costs and marginal costs needed in the determination of the DUE and DSO solutions. This DTA framework is then combined with the CTM for HD traffic proposed previously, followed by the extension of the DUE and DSO problem formulations and all the relevant algorithms to the context of HD traffic. Other contributions of this work include a comprehensive review of the studies conducted in the context of HD traffic, the proposal of a new methodology for the con- struction of driving cycles for cities with HD traffic, and the introduction of a backpropagation technique to efficiently compute the costs needed to calculate the DTA solutions.
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Shah, Syed Abid Ali. "A macroscopic traffic flow model for adverse weather conditions." Thesis, 2017. http://hdl.handle.net/1828/7881.
Full textAbstract:
Adverse weather has a direct effect on traffic congestion and the time delay on roads.
Weather conditions today are changing rapidly and are more likely to have a severe effect on traffic in the future. Although different measures have been taken to mitigate these conditions, it is important to study the impact of these events on road conditions and traffic flow. For example, the surface of a road is affected by snow, compacted snow and ice. The objective of this thesis is to characterize the effect of road surface conditions on traffic flow. To date, traffic flow under adverse weather conditions has not been characterized. A macroscopic traffic flow model based on the transition velocity distribution is proposed which characterizes traffic behavior during traffic alignment under adverse weather conditions. The model proposed realistically characterizes the traffic flow based on snow, compacted snow, and ice. Results are presented which show that this model provides a more accurate characterization of traffic flow behavior than the well known Payne-Whitham model.Graduate
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Domingues, Tiago Mendes. "Dynamic network modelling and simulation for air traffic flow analysis." Master's thesis, 2011. http://hdl.handle.net/10400.6/3638.
Full textAbstract:
This dissertation describes the achievement of a set of equations in order to represent
a discrete model for air traffic dynamics in terminal areas. Such a mathematical model
could be used to investigate the occupation of a TMA‡ at a single instant and has the
potential to be used on the prediction of a future occupation.
There are safety and legal limits to how many aircraft should be inside a TMA at
once. It could also be useful for an Air Traffic Controller to predict a future overoccupation and thus being able to prevent it. That is why there is an interest to know
at each instant an estimate of how many aircraft are in a specific TMA.
The idea behind it was to make a Control Theory approach so that the same classical tools used in other topics such as flight dynamics could be applied to this subject.
In order for that to happen there were needed some Network notions along with navigation formulae.
If an aircraft leaves one place we know a priori that he will follow a path and later
enter a certain TMA, unless something goes wrong. That information is known even
before lift off. It limits our monitoring window and we can now focus on the physical
existence of an aircraft in or out a determined TMA.
Every aircraft within a radius of several nautical miles, depending on each TMA,
does belong to that TMA. A transition between areas is considered a control input.
Knowing the initial amount of aircraft on the zero instant at a particular site we
can calculate the following instant state by adding the arrivals and subtracting the
departures. This system has mass conservation in a sense that aircraft don’t just
disappear - instead they move around and the total number of aircraft on the system
remains the same.
Depending on the complexity of the system other separated states can be monitored and we could separate the grounded aircraft from the airborne aircraft; allow
mid-flight decision change to go to a different TMA, etc.
Data retrieved from the website www.localizatodo.com together with Octave Software allowed the validation of the model. On this website the captured transponder
signals are transformed into several bits of information from which were retrieved the
ones useful: Longitude, Latitude and time stamp. The equations performed as they
should, making them applicable to a real scenario, since the utilized data are in fact
coming themselves from a real scenario and they are not invented.
The first two models are slightly different from the third. One concerns the TMA as
if they were contiguous and another considers the paths among each other. They are
steps towards an objective, rather than a final solution.
The inclusion of a sigmoid function to the model was the latest work to be done.
It has to do with the prediction and how much would an incoming airship weight
on the eyes of the Air Traffic Controller. There is a need to remove abrupt changes
inherent to the model in a way that an aircraft would gradually become present on the
arriving TMA from the moment he lifted off the departing TMA, instead of just showing up on the arriving TMA and thus giving no anticipation opportunity to the air traffic
controllers.
In a future work an estimator, such as a Kalman Filter, should be added to this
model or even an improved similar model, since it has the flexibility to incorporate
new features in a simple way. There is an explanation on how to perform these additions.
This work could be used as a foundation for the implementation of a warning to
the Air Traffic Controllers of the occupation status. Not only that but it could be a
module on a fully automatic Airspace Controller or even other applications yet to be
considered. It could even be applied on the traffic of buses (coaches) and it can be
extrapolated to many other fields.Esta dissertação descreve o processo pelo qual se encontraram um conjunto de equações representativas de um modelo discreto de dinâmica de tráfego aéreo em zonas terminais. Tal modelo matemático poderá ser utilizado para investigar a ocupação de uma TMA† num instante singular, tendo o potencial de ser utilizado para prever a ocupação futura. Existem limites de segurança e legais acerca de quantas aeronaves deverão estar dentro de uma TMA de uma só vez. Poderia também ser usável por um Controlador de Tráfego Aéreo em prever uma futura sobre-ocupação e portanto ser capaz de a prevenir. É por isso que existe um interesse em saber a cada instante uma estimativa de quantas aeronaves estão numa TMA específica. A idéia por detrás deste assunto foi a de fazer uma abordagem de Teoria de Controlo de forma a que as ferramentas clássicas utilizadas noutros tópicos, tais como dinâmica de voo, pudessem ser aplicadas a este problema. Para que isso fosse possível eram necessárias noções de Network a par de fórmulas de navegação. Se uma aeronave deixa um determinado sítio sabemos a priori que vai seguir um caminho e mais tarde vai entrar numa TMA específica, a menos que algo corra mal. Essa informação é sabida antes sequer de haver descolagem. Isto permite-nos limitar a nossa janela de monitorização e podemos agora focar-nos na existência física de uma aeronave dentro ou fora de uma determinada TMA. Qualquer aeronave num raio de várias milhas náuticas, dependendo de cada TMA, pertence a essa TMA. Uma transição entre áreas é considerado um input de controlo. Sabendo a quantidade inicial de aeronaves no instante inicial num determinado sítio, podemos calcular o instante seguinte adicionando as chegadas e eliminando as partidas. Este sistema tem conservação de massa no sentido em que as aeronaves não desaparecem. Ao invés elas movem-se de um lado para o outro e o número total de aeronaves num sistema continua o mesmo. Dependendo da complexidade do sistema, outros estados separados poderão ser monitorizados e podemos separar as aeronaves no chão das do ar; permitir alteração de decisão a meio de um voo para dirigir-se a uma TMA diferente, etc. Dados obtidos do sítio web www.localizatodo.com em conjunto com o Software Octave, permitiram a validação do modelo. Neste sítio web os sinais de transponder capturados são depois transformados em vários bits de informação dos quais se retiram os úteis: Longitude, Latitude e carimbo de tempo. As equações comportaram-se como deviam, fazendo este modelo aplicável a um cenário real, já que os dados utilizados de facto provêm eles mesmos de de um cenário real e não de um inventado. Os primeiros dois modelos são ligeiramente diferentes do terceiro. Um deles é relativo às TMA como se elas fossem contíguas umas das outras e segundo já considera os caminhos entre elas. São passos no caminho de um objectivo, em vez de serem uma solução final. A inclusão de uma função sigmóide ao modelo foi o último trabalho a ser efectuado. Tem que ver com a previsão e de quanto pesaria uma aeronave a chegar aos olhos do Controlador de Tráfego Aéreo. Existe uma necessidade de remover mudanças abruptas inerentes ao modelo, de forma que uma aeronave fosse ficando presente gradualmente na TMA de chegada a partir do momento que tenha descolado da TMA de partida, ao invés de somente aparecer na TMA de chegada e assim sendo não dar oportunidade de antecipação aos Controladores de Tráfego Aéreo. Num trabalho futuro um estimador, tal como um Filtro de Kalman, deveria ser adicionado a este modelo ou até a um modelo similar melhorado, já que este tem a flexibilidade de incorporar novas características de uma forma expedita. Existe uma explicação em como fazer essa adições. Este trabalho poderia ser utilizado como fundação para a implementação de um sistema de alerta aos Controladores de Tráfego Aéreo do estado de ocupação. Não só isso como também poderia ser um módulo num Controlador Automático de Espaço Aéreo e mesmo noutras aplicações ainda por considerar. Poderia até ser aplicado no tráfego de autocarros ou poderia ser extrapolado para muitos outros campos.
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Patnaik, Ashish Kumar. "Entry Capacity Modelling of Roundabouts under Heterogeneous Traffic Flow Conditions." Thesis, 2018. http://ethesis.nitrkl.ac.in/9765/1/2018_PHD_AKPatnaik_513CE1011_Entry.pdf.
Full textAbstract:
The objectives of this study is to develop entry capacity models for both un-signalized and signalized roundabouts under heterogeneous traffic flow conditions. Required data have been collected from 27 un-signalized and 15 signalized roundabouts spanning across 11 states of India. To develop the entry capacity model for un-signalized roundabouts, initially two types of models are developed namely, empirical models and gap acceptance based models. Empirical models are based upon statistical approach whereas gap acceptance models rely on the driver’s behaviour and vehicle-to-vehicle interactions. An empirical model is developed by taking geometric variables and circulating flow as explanatory variables, while the gap acceptance based model is developed by employing critical gap, follow up time and circulating flow as explanatory variables. To reflect the driver behavioral habits and site conditions in a single model, semi-analytical model is developed in this study. In order to reflect the actual driver behavioral habits under local conditions,critical gap and follow up time are estimated by using proposed Influence area for gap acceptance (INAGA) method in this study. The critical gap values found to be varying from 0.54 s to 2.87 s, which are nearly half the values (4 s to 4.6 s) of developed nations like USA and European countries. To ascertain the applicability of proposed INAGA method, the said method is compared with traditionally followed raff and equilibrium of probabilities method. It is observed that the critical gap values estimated by equilibrium of probabilities method differs from corresponding values estimated by INAGA method by 2.10 to 27.03 %. While the values obtained by raff method are quite similar and differ by 0.41 to 3.27 % only. Models based on Artificial intelligence techniques such as Artificial Neural Network (ANN), Generic Programming (GP), Adaptive Neuro Fuzzy Inference Systems (ANFIS) are also developed for un-signalized roundabouts. A comparative study on all developed models is carried out. Also signalized roundabout entry capacity model is developed by using the concept of signalized analogy in which geometric variables and signalization variables are taken as explanatory variables. It has been observed from the collected data set that the Composition of traffic varies as (0.14 to 55.07)%, (10.52 to 78.9)%, (6.84 to 77.9)%, (0.06 to 36.51)%,(0.04 to 7.49)% for heavy vehicles (HV), light motor vehicles (LMV), Motorcycles (MC)/scooters, Bicycles (BC) and Animal drawn vehicles (ADV)/Human drawn vehicles (HDV) respectively at selected un-signalized roundabouts. Similarly, the Composition of traffic varies as(18.92-77.18)%, (2.92- 33.28)%, (11.84-57.58)%, (1.71-11.63)%,(0.41-13.48)%, (0.14-0.78)% and (2.27-26.54)% for two wheelers (2W), Three wheelers (3W), Cars, Light commercial vehicles (LCV), Bus, Truck and Cycle at selected signalized roundabouts respectively. The co-efficient of determination (R2) value of empirical based model and gap acceptance based model are found to be 0.93 and 0.78 respectively. And the p-value in the test of Analysis of variance (ANOVA) is found to be 0.00 (p-value<0.05) for both empirical and gap acceptance based model, which signifies that the models are statistically fit at 95% confidence level. By developing the semi-analytical model, the R2 and p-value in the test of ANOVA are found to be 0.92 and 0.00 respectively. And from the significance test, the value of Nash-Sutcliffe co-efficient (E), mean (μ) and standard deviation (σ) are found to be (0.91, 0.99, 0.13) and (0.87, 0.93, 0.11) respectively which signifies that the proposed semi-analytical model is statistically significant at 95% confidence level. It is observed that Bayesian regularization back propagation training function (TrainBR), in combination with hyperbolic tangent sigmoid transfer function (Tansig) based ANN model has highest R2 value of 0.97 and lowest root mean square error (RMSE) value of 167.89 among all ten models developed. Therefore, this model is chosen for the capacity prediction in this study. Among three developed models such as Genetic Programming (GP), Age layered population structure Genetic Programming (ALPS GP) and Grammatical Evolution Genetic Programming (GEGP); GEGP model is found to be best fit by employing modified rank index (MRI) among these GP based models. By applying multiple non-linear regression analysis (MNLR), the proposed signalized roundabout capacity model is found to be best fit at 95 % confidence level in which the R2 is measured to be 0.95. Sensitivity analysis reported that weaving section variables such as weaving length (Wl), weaving width (WW) and signal phase variable such as green time (G) are major variables for the determination of signalized roundabout entry capacity. Among the proposed un-signalized roundabout entry capacity models such as semi-analytical model, ANN model, GEGP model and ANFIS model; ANFIS model placed in 1st rank, whereas both ANN and GEGP model are placed in 2nd rank and Semi-analytical model is placed in 3rd rank respectively. It is ascertained from statistical test that ANFIS model holds good for roundabout capacity estimation. But from practical application point of view, this model seems to be poor as expression of the equation could not be built up. Whereas, in comparison to ANFIS model, Semi-analytical model can be widely acceptable for its simplicity and manageability. Hence Semi-analytical model is recommended for the estimation of roundabout entry capacity under heterogeneous traffic flow conditions. Regression based models are simple from application point of view but these models have shown higher prediction error in comparison to Artificial intelligence based models. Sensitivity analysis reports that critical gap is the prime variable and sharing 18.43 % in the semi-analytical based roundabout entry capacity model. As compared to Girabase formula (France), Brilon wu formula (Germany) and HCM 2010 models, the proposed semi-analytical model is quite reliable under low to medium range of traffic volumes. The proposed model is suggested for application in the field by practitioners because the model provides unique equation for prediction. The priority of explanatory variables can be easily examined in the proposed model. The model can be easily modified by inclusion or exclusion of geometric variables. The model can be widely acceptable for its simplicity and manageability. Sensitivity analysis is quite useful for planning and design prospective because of major contributing variables are easily identified in the proposed model. The common PCU factors are determined to convert the heterogeneous traffic into homogeneous one, thus it give a reliable estimation of roundabout entry capacity. These findings will be helpful for the researchers, planners and designers for making key decision.
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Mukundane, Edwige. "Urban traffic flow prediction, a spatial-temporal approach." Master's thesis, 2021. http://hdl.handle.net/10362/113896.
Full textAbstract:
Dissertation submitted in partial fulfilment of the requirements for the Degree of Master of Science in Geospatial TechnologiesCurrent advances in computational technologies such as machine learning combined with traffic data availability are inspiring the development and growth of intelligent transport Systems (ITS). As urban authorities strive for efficient traffic systems, traffic forecasting is a vital element for effective control and management of traffic networks. Traffic forecasting methods have progressed from traditional statistical techniques to optimized data driven methods eulogised with artificial intelligence. Today, most techniques in traffic forecasting are mainly timeseries methods that ignore the spatial impact of traffic networks in traffic flow modelling. The consideration of both spatial and temporal dimensions in traffic forecasting efforts is key to achieving inclusive traffic forecasts. This research paper presents approaches to analyse spatial temporal patterns existing in networks and goes on to use a machine learning model that integrates both spatial and temporal dependency in traffic flow prediction. The application of the model to a traffic dataset for the city of Singapore shows that we can accurately predict traffic flow up to 15 minutes in advance and also accuracy results obtained outperform other classical traffic prediction methods.
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(9806345), Yi Hu. "Traffic flow modelling, control and simulation utilising artificial intelligence and modern control technologies." Thesis, 2008. https://figshare.com/articles/thesis/Traffic_flow_modelling_control_and_simulation_utilising_artificial_intelligence_and_modern_control_technologies/13436198.
Full textAbstract:
"An efficient traffic signal control system is an essential tool to keep smooth, safe traffic environment in most metropolitan cities. In this thesis, artificial intelligence techniques, namely fuzzy logic technologies and evolutionary algorithms were used to implement and optimise a real multi-approach intersection, and at the same time, the pedestrian crossings were also taken into account to increase the complication and difficulty of regulating traffic flow. The main goals of this research are to shorten waiting time for each vehicle and to avoid traffic congestion"-- Abstract.
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Stazic, Branko. "The development of custom vehicle fleet profiles for traffic microsimulation modelling." 2005. http://arrow.unisa.edu.au:8081/1959.8/82729.
Full textAbstract:
The classification of vehicle types and their attributes for various traffic modelling exercises is a common occurrence. The increasing use of microsimulation packages, which are based on modelling individual vehicles through the road network, points to the importance of having proper vehicle attributes specified in order to achieve the modelling results that match real-life conditions.The use of a customised vehicle fleet instead of the default types that are usually built into microsimulation software will allow more accurate estimation of traffic performance indicators, such as speeds, travel times, capacity, fuel consumption etc. Most notably the accurate classification of vehicles is essential for reliable vehicle emissions modelling to occur, since the type and fuel used by vehicles has a significant effect on their emissions performance. To this end there are a number of databases that can be used for vehicle classification, these include but are not limited to: Australian Bureau of Statistics Motor Vehicle Census Data; Austroads Vehicle Classifications; Fleet composition models produced by Bureau of Transport Economics.
This thesis describes the development of the customised vehicle fleet to be used in Paramics microsimulation modelling package by Quadstone in the UK. Vehicle fleet profiles were developed for South Australian urban and rural conditions based on Australian Bureau of Statistics Motor Vehicle Census data and supplemented with other sources of vehicle kinematics and physical characteristics.
Thesis (MEng(TransportSystemsEng))--University of South Australia, 2005
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Habibi, D. "Performance analysis & traffic modelling in broadband integrated services digital networks." Thesis, 1995. https://eprints.utas.edu.au/19939/7/Habibi_whole_thesis_ex_pub_mat.pdf.
Full textAbstract:
Broadband Integrated Services Digital Networks (B-ISDN) will provide the ability to support a wide range of services using Asynchronous Transfer Mode (ATM) as the transfer technique. While ATM provides the flexibility to integrate a large number of services economically, the challenge to teletraffic engineers is to ensure that an acceptable grade of service is provided for each type of traffic. Research in network performance and traffic modelling is required to develop network operating strategies which will meet these goals.
This thesis is mainly concerned with performance analysis models for B-ISDN. In performance modelling of access nodes, several strategies are studied for mixing loss-sensitive traffic with delay-sensitive traffic in both TDM and ATM environments. The performance of these strategies are analysed by different methods. Next, the problem of statistical multiplexing of interactive data, interactive images and variable bit rate (VBR) video traffic in an ATM access node is considered. In this situation, the effect of link rate to source rate ratio and also the effect of priority encoding of the VBR video on the performance of the ATM access node are studied. Next, a strategy is proposed for statistically multiplexing a range of constant bit rate services with an aggregate of variable bit rate services at an ATM access node. Performance parameters for both service types are evaluated by analysis and also by simulation.
Accurate source models are an essential component of any access node problem. The traffic generated from video services will greatly influence the overall performance and data requirements in B-ISDN, and the next area considered in this thesis is modelling of video traffic. Several video models in the literature are reviewed and a few models based on the concept of hidden Markov models are examined for modelling variable bit rate video traffic. Network performance based on these models is investigated.
Another area that is covered in this thesis is performance modelling for those parts of the network that are subject to traffic with periodically varying rates. A computational probability analysis is presented for queues with cyclo-stationary arrivals and/or cyclo-stationary service rates. Such traffic patterns may arise in a variety of telecommunication and computer networks, including B-ISDN.
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BALZOTTI, CATERINA. "Second order traffic flow models on road networks and real data applications." Doctoral thesis, 2021. http://hdl.handle.net/11573/1538080.
Full textAbstract:
This thesis concerns macroscopic traffic models and data-driven models. In the first part we deal with the extension of Generic Second Order Models (GSOM) for traffic flow to road networks. We define a Riemann Solver at the junction based on a priority rule, providing an iterative algorithm able to build the solution to junctions with n incoming and m outgoing roads. The logic underlying our solver is the following: the flow is maximised respecting the priority rule, but the latter can be modified if the outgoing road supply exceeds the demand of the road with higher priority. We provide bounds on the total variation of waves interacting with the junction, giving explicit computations for intersections with two incoming and two outgoing roads. These estimates are fundamental to prove the existence of weak solutions to Cauchy problems on networks via Wave-Front-Tracking.
GSOM are used to analyse traffic dynamics and their effects on the production of pollutant emissions. First we apply the proposed Riemann Solver to simulate traffic dynamics on diverge and merge junctions and on roundabouts obtained by combining these two types of intersection. Then, we propose a methodology to estimate the pollutant emissions deriving from traffic dynamics. The emission model is calibrated and validated using the NGSIM dataset of real trajectory data. Furthermore, we set up a minimisation problem aimed at finding the optimal priority rule for our Riemann Solver that reduces the emission rates due to the traffic dynamic. Finally, we analyse some chemical reactions which lead to the production of ozone, focusing on the effects on pollution of the presence of traffic lights on the road.
Next, we introduce a macroscopic two-dimensional multi-class traffic model on a single road, aimed at including lane-changes and different types of vehicles. The multi-class model consists of a coupled system of conservation laws in two space dimensions. Besides the study of the Riemann problems, we present a Lax-Friedrichs type discretisation scheme and we recover the theoretical results by means of numerical tests. We then calibrate and validate the multi-class model with real trajectory data and we test its ability of simulating vehicles overtaking.
Finally, we present a new methodology to recover mass movements from snapshots of its distribution. To this end we put in place an algorithm based on the combination of two methods: first, we use the dynamic mode decomposition to create a system of equations describing the mass transfer; second, we use the Wasserstein distance to reconstruct the underlying velocity field that is responsible for the displacement. We conclude this part with a real-life application: the algorithm is employed to study the travel flows of people in large populated areas using, as input, presence data of people in given region domains derived from the mobile phone network, at different time instants.
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Scheffer, Marten F. "Fuzzy logic modelling and management strategy for packet-switched networks." Thesis, 2012. http://hdl.handle.net/10210/7355.
Full textAbstract:
D.Ing.Conventional traffic models used for the analysis of packet-switched data are Markovian in nature and are based on assumptions, such as Poissonian arrivals. The introduction of packet oriented networks has resulted in an influx of information highlighting numerous discrepancies from these assumptions. Several studies have shown that traffic patterns from diverse packet-switched networks and services exhibit the presence of properties such as self-similarity, long-range dependencies, slowly decaying variances, "heavy tailed" or power law distributions, and fractal structures. Heavy Tailed distributions decay slower than predicted by conventional exponential assumptions and lead to significant underestimation of network traffic variables. Furthermore, it was shown that the statistical multiplexing of multiple packet-switched sources do not give rise to a more homogenous aggregate, but that properties such as burstiness are conserved. The results of the above mentioned studies have shown that none of the commonly used traffic models and assumptions are able to completely capture the bursty behaviour of packet- and cellbased networks. Artificial Intelligent methods provide the capability to extract the inherent characteristics of a system and include soft decision-making approaches such as Fuzzy Logic. Adaptive methods such as Fuzzy Logic Self-learning algorithms have the potential to solve some of the most pressing problems of traffic Modelling and Management in modern packet-switched networks. This dissertation is concerned with providing alternative solutions to the mentioned problems, in the following three sub-sections; the Description of Heavy Tailed Arrival Distributions, Timeseries Forecasting of bursty Traffic Intensities, and Management related Soft Decision-Making. Although several alternative methods, such as Kalman Filters, Bayesian Distributions, Fractal Analysis and Neural Networks are considered, the main emphasis of this work is on Fuzzy Logic applications.
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Liu, Mingzhe. "Theoretical investigation of traffic flow : inhomogeneity induced emergence : a dissertation presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Computer Science at Massey University, Auckland, New Zealand." 2010. http://hdl.handle.net/10179/1350.
Full textAbstract:
This research work is focused on understanding the effects of inhomogeneity on traffic flow by theoretical analysis and computer simulations. Traffic has been observed at almost all levels of natural and manmade systems (e.g., from microscopic protein motors to macroscopic objects like cars). For these various traffic, basic and emer- gent phenomena, modelling methods, theoretical analysis and physical meanings are normally concerned. Inhomogeneity like bottlenecks may cause traffic congestions or motor protein crowding. The crowded protein motors may lead to some human diseases. The congested traffic patterns have not been understood well so far. The modelling method in this research is based on totally asymmetric simple exclusion process (TASEP). The following TASEP models are developed: TASEP with single inhomogeneity, TASEP with zoned inhomogeneity, TASEP with junction, TASEP with site sharing and different boundary conditions. These models are motivated by vehicular traffic, pedestrian trafficc, ant traffic, protein motor traffic and/or Internet traffic. Theoretical solutions for the proposed models are obtained and verified by Monte Carlo simulations. These theoretical results can be used as a base for further developments. The emergent properties such as phase transitions, phase separations and spontaneous symmetry breaking are observed and discussed. This study has contributed to a deeper understanding of generic traffic dynamics, particularly, in the presence of inhomogeneity, and has important implications for explanation or guidance of future traffic studies.
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Min, Geyong, and X. Jin. "Analytical Modelling and Optimization of Congestion Control for Prioritized Multi-Class Self-Similar Traffic." 2013. http://hdl.handle.net/10454/9689.
Full textAbstract:
NoTraffic congestion in communication networks can dramatically deteriorate user-perceived Quality-of-Service (QoS). The integration of the Random Early Detection (RED) and priority scheduling mechanisms is a promising scheme for congestion control and provisioning of differentiated QoS required by multimedia applications. Although analytical modelling of RED congestion control has received significant research efforts, the performance models reported in the current literature were primarily restricted to the RED algorithm only without consideration of traffic scheduling scheme for QoS differentiation. Moreover, for analytical tractability, these models were developed under the simplified assumption that the traffic follows Short-Range-Dependent (SRD) arrival processes (e.g., Poisson or Markov processes), which are unable to capture the self-similar nature (i.e., scale-invariant burstiness) of multimedia traffic in modern communication networks. To fill these gaps, this paper presents a new analytical model of RED congestion control for prioritized multi-class self-similar traffic. The closed-form expressions for the loss probability of individual traffic classes are derived. The effectiveness and accuracy of the model are validated through extensive comparison between analytical and simulation results. To illustrate its application, the model is adopted as a cost-effective tool to investigate the optimal threshold configuration and minimize the required buffer space with congestion control.