Thesis (MEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Peak mornmg traffic-flow data were obtained from video footage of three representative freeway sections on the Nl and N2 westbound towards Cape Town. Flow, speed, and density measurements were made from the footage with the aid of a stopwatch. Many researchers (2-12) have originated and developed models to describe the relationships between traffic flow characteristics (speed, flow, and density) on freeways. In this report, a number of these models have been investigated with data obtained from South African freeways. The ability of each model to predict flow parameters over the entire range of data was evaluated with the aid of statistical methods. The tests were performed by regressing average speed vs. average density. Flow-density and speed-flow relationships were derived through application of the steady-state equation (2.6). In each case, a final model was chosen through visual inspection that consisted of two separate curves, one for the uncongested flow regime and one for the congested flow regime. Furthermore, speed-flow relationships were examined for individual lanes and compared to relationships established for average lanes. The models were also compared to models obtained from overseas studies (1,16,19) as well as from studies done locally (17). A secondary objective of this study is to investigate the performance of existing freeway facilities through application of the relevant models to the traffic-flow data of a particular facility. The current peak-morning performance of the N2 freeway section is investigated in terms of travel-time and travel cost. The particular study section consists of three lanes, the right hand lane being an HOY lane dedicated to taxis and buses. Different hypothetical cases are investigated. The first hypothetical case is an investigation into the traffic situation on the freeway section without the influence of the HOY lane. The second hypothetical case investigates the traffic situation on the section with perfect operation of the HOY lane. The current performance of the N2 section is compared to the performance of each of the hypothetical cases. / AFRIKAANSE OPSOMMING: Oggend-spits verkeersvloei data is verkry vanaf drie verteenwoordigende seksies op die Nl en N2 deurpaaie naby Kaapstad met die gebruik van 'n video kamera. Vloei, spoed, end digtheid opnames is gemaak met behulp van 'n stophorlosie. Verskeie navorsers (2-12) het modelle gepostuleer en ontwikkelom die verhoudings tussen verkeersvloei eienskappe (spoed, volume, en digtheid) op deurpaaie te beskryf. In hierdie verslag word 'n aantal van hierdie modelle ondersoek met data wat verkry is van Suid-Afrikaanse deurpaaie. Die vermoë van elke model om vloei eienskappe oor die hele bestek van die data te voorspel is geëvalueer met behulp van statistiese metodes. Statistiese toetse behels 'n regressie analise van gemiddelde spoed teenoor gemiddelde digtheid. Volume-digtheid en spoed-volume verwantskappe is direk afgelei vanaf Vergelyking 2.6. Vir elke geval is 'n finale model m.b.v. visuele inspeksie gekies wat bestaan het uit twee afsonderlike kurwes, een kurwe vir die vryvloei regime en 'n ander kurwe vir hoë-digtheid toestande. Verder word spoedvolume verwantskappe vir afsonderlike deurpad-lane ondersoek en vergelyk met verwantskappe wat verkry is vir gemiddelde lane. Die modelle word ook vergelyk met modelle wat verkry is vanaf oorsese studies (1,16,19), sowel as met modelle wat plaaslik verkry is (17). 'n Sekondêre doel van hierdie studie is om die prestasie van bestaande deurpadfasiliteite te ondersoek deur die verskillende modelle aan te wend tot die verkeersvloei data van 'n betrokke fasiliteit. Die prestasie van die N2 deurpad seksie gedurende oggend-spits verkeer is ondersoek in terme van reistyd en ryskoste. Die betrokke seksie bestaan uit drie lane, waarvan die regter laan gereserveer is vir busse en taxis. Verskeie hipoteses is ook ondersoek. Die eerste hipotese is 'n ondersoek na die verkeers-vloei kondisie op die seksie sonder die invloed van die bus- en taxi-laan. Die tweede hipotese ondersoek die seksie met perfekte werking van die bus- en taxilaan. Die huidige prestasie van die N2 seksie is vergelyk met die prestasie van elk van die hipoteses.

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

Made available in DSpace on 2016-04-04T18:31:20Z (GMT). No. of bitstreams: 1 Alberto Lotito.pdf: 2153365 bytes, checksum: 3433c9bb5371bcce62f119c4593fe360 (MD5) Previous issue date: 2007-12-05 / This work intends to perform end-to-end traffic engineering through simulations in broadband multiprotocol networks and evaluate used parameters. We ve proposed and tested parameters used by the network administrator to dimension the action of an algorithm for Traffic Engineering. We dedicated special attention to IP networks interconnected to MPLS networks. Through simulations, we ve addressed questions of performance optimization, evaluating the network packet losses and compare the results with packet loss in the traditional OSPF network achieving improvements of up to 50%. This work contributes with improvements in traffic performance for real world networks, developing practical application since the traditional IP networks up to the present MPLS networks and also for mixed technologies. / Este trabalho tem como objetivos realizar simula??es de engenharia de tr?fego fim a fim em redes que trabalham com protocolos distintos e avaliar par?metros usados. Propusemos e testamos par?metros que servem para que o operador da rede dimensione a atua??o de um algoritmo para engenharia de tr?fego. Demos especial aten??o ?s redes que trabalham com IP interconectando-se a redes MPLS. Executando diversas simula??es, trabalhamos quest?es de melhoria de desempenho por meio de avalia??o da perda de pacotes nas redes testadas comparando-se os resultados com as tradicionais redes com protocolo OSPF e chegando a melhoria de at? 50% se comparado com este. Este trabalho contribui com melhorias em engenharia de tr?fego em redes do mundo real, desenvolvendo aplica??o pr?tica desde as tradicionais redes IP at? as atuais redes MPLS e tamb?m em redes de tecnologias mistas.

Submitted by Jaqueline Silva (jtas29@gmail.com) on 2014-09-04T19:36:30Z No. of bitstreams: 2 Walid Abdala Rfaei Jradi.pdf: 10830820 bytes, checksum: 605fdfee3d5d31cec3e54ce425a7ab68 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2014-09-04T19:36:30Z (GMT). No. of bitstreams: 2 Walid Abdala Rfaei Jradi.pdf: 10830820 bytes, checksum: 605fdfee3d5d31cec3e54ce425a7ab68 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2008-09-23 / The present work proposes an architecture of a Decision Support System for modelling, simulating and visualizing urban traffic, using a mathematical model adjusted to the reality of the Brazilian transit, as well as an appropriate choice of data for this context. To prove the viability of the architecture, an interactive tool, called PET-Gyn, was implemented, with a Web graphical interface. The simulation of the traffic was based on algorithms already existing in the literature, with proven effectiveness, but with adaptations that had been shown necessary. The data applied to the urban traffic is composed of information obtained from GoogleMaps API, data on the road mesh and the collection of the traffic demands measured in a region of the city of Goiânia-GO. The tool allows the visualization of basic information about the traffic in a city and offers forms of interaction to simulate the effect of possible reorganizations of the road net. / O presente trabalho propõe uma arquitetura de Sistema de Apoio à Decisão para modelar, simular e visualizar o tráfego urbano, usando um modelo matemático adequado à realidade do trânsito brasileiro, bem como uma modelagem de dados apropriada a esse contexto. Para comprovar a viabilidade da arquitetura, foi implementado uma ferramenta interativa, chamada PET-Gyn, com interface gráfica para a Web. A simulação do tráfego foi baseada em algoritmos existentes na literatura de comprovada eficácia, mas com adaptações que se mostraram necessárias. A modelagem de dados aplicada ao tráfego urbano é composta de informações retiradas da API do GoogleMaps, de dados sobre a malha viária e da coleta das demandas de tráfego medido em uma região da cidade de Goiânia-GO. A ferramenta permite a visualização de informações básicas sobre o tráfego em uma cidade e oferece formas de interação para simular o efeito de possíveis reestruturações da rede viária.

Travel times, operating speeds, and service reliability influence costs and service attractiveness. This paper outlines an approach to quantify how these metrics change after a modification of roadway design or transit routes using archived transit data. The Tri-County Metropolitan Transportation District of Oregon (TriMet), Portland's public transportation provider, archives automatic vehicle location (AVL) data for all buses as part of their bus dispatch system (BDS). This research combines three types of AVL data (stop event, stop disturbance, and high-resolution) to create a detailed account of transit behavior; this probe data gives insights into the behavior of transit as well as general traffic. The methodology also includes an updated approach for confidence intervals estimates that more accurately represent of range of speed and travel time percentile estimates. This methodology is applied to three test cases using a month of AVL data collected before and after the implementation of each roadway change. The results of the test cases highlight the broad applicability for this approach to before-and-after studies.

During the last years, MultiProtocol Label Switching (MPLS) has been deployed by most large Service Providers (SP). The main driver for MPLS deployment is the ability to provide new services with stringent Service Level Agreements (SLAs) such as layer-2 and layer-3 Virtual Private Networks (VPNs) as well as Voice and Video over IP. Most of these services are already deployed inside single SP networks. However, customers now require world-wide VPN and VoIP services. Therefore, SPs need to collaborate to offer these services across multiple SP networks. Inside a single SP network, each node usually knows the complete topology of the network with the load and delay of all the links. Based on this information, each router is able to compute constrained paths toward any other router inside the SP network. Then, it can establish a connection and reserve resources along the computed path with the Resource reSerVation Protocol (RSVP-TE). However, when services with stringent requirements must cross multiple SP networks the computation of the path becomes a problem. Routers in different SP networks exchange routing information by using the Border Gateway Protocol (BGP). BGP provides reachability information. It does not distribute complete topology, delay and bandwidth information. One way to provide guaranteed services crossing different SPs is to delegate the computation of the paths to a Path Computation Element (PCE) that learns the topology of the different SPs. However, this requires that SPs reveal information that they usually consider confidential, their topology. In this thesis, we perform active measurements to show the difficulty to engineer the interdomain traffic with BGP. MPLS together with RSVP-TE provide much more control on the traffic. We define extensions to RSVP-TE for the protection of inter-AS MPLS paths. The aim is to be able to provide the same service guarantees as inside a domain while keeping the internal topology of SPs confidential, as required by SPs. We propose and evaluate distributed techniques relying on PCEs for the computation of interdomain constrained paths respecting the latter confidentiality requirement.

The Internet traffic is constantly increasing following the emergence of new network applications like social networks, peer-to-peer, IP phone or IP television. In addition, these new applications request better path availability and path quality. Indeed the efficiency of these applications is strongly related to the quality of the underlying network. In that context network operators make use of traffic engineering techniques in order to improve the quality of the routes inside their network, but also to reduce the network cost of increased traffic handling with a better utilization of existing resources. This PhD thesis covers several topics of Traffic Engineering and Fast Restoration in IP/MPLS networks. Our first contribution is related to the definition of a well-engineered network. In the literature mathematical formulation of Traffic Engineering (TE) requirements are very diverse. We have thus performed a comparative study of many objective functions, in order to differentiate them and choose in a rational way the one that best reflects Traffic Engineering goals. We have also designed a method approaching optimal TE, whereby we divide the traffic matrix in N sub-matrices and route them independently, based on the derivatives of the objective function. The second topic addressed in this work concerns link weight optimizers (LWOs). Link weight optimization is the traffic engineering {it "standard"} technique in networks running link state routing protocols (which are widely used in transit networks). These link weight optimizers suffer from several limitations due to the BGP (Border Gateway Protocol) Hot-Potato rule, which is basically not considered by such optimizers. Therefore we have proposed a BGP-aware link weight optimization method that takes problematic Hot-Potato effects into account, and even turns them into an advantage. We have also studied how LWOs behave in big networks which have to use BGP route reflectors. Finally we have studied whether forwarding loops can appear or not when traffic is split among multiple equivalent egress routers, an optional BGP feature that we did use in our Hot-Potato aware LWO. Our last contribution concerns network resilience. We have proposed a solution for a rapid recovery from a link or node failure in an MPLS network. Our solution allows a decentralized deployment combined with a minimal bandwidth usage while requiring only reduced amount of information to flood in the network. This method is the first that makes possible a decentralized deployment combined with an optimal resource consumption. To easily simulate and test the methods proposed in this work, we have also contributed to the development of TOTEM - a TOolbox for Traffic Engineering Methods.

In roadway projects, design exceptions are implemented when the project site consists of one or more substandard design elements. The objective of this thesis is to conduct an initial investigation for a monitoring program for the safety performance of design exceptions in Georgia. A total of 467 projects containing design exceptions were reported in Georgia from 1995 to 2011, and from this crash data for 179 projects from 2003 to 2008 were sampled. The crash data collected in this research pertains to all roadway segments within the projects and is not necessarily related to the design exceptions. Future efforts will be required to explore potential connections between the crash rates and design exceptions. The annual crash results generally revealed a high variability and randomness in the data. For this reason, the average 3-year crash frequencies before design exception approval date and after it were calculated to determine the safety performance for projects containing design exceptions. A method for determining expected results using the Highway Safety Manual (HSM) predictive method is also discussed. The findings will be used to guide future research on design exceptions and mitigation measures to improve roadway safety.

This thesis presents a framework for motor vehicle detection-tracking surveillance systems. Given an optimized object detection template, the feasibility and effectiveness of the methodology is considered for vehicle counting applications, implementing both a filtering operation of false detection, based on the speed variability in each segment of traffic state, and an occlusion handling technique which considers the unusual affine transformation of tracking subspace, as well as its highly fluctuating averaged acceleration data. The result presents the overall performance considering the trade-off relationship between true detection rate and false detection rate. The filtering operation achieved significant success in removing the majority of non-vehicle elements that do not move like a vehicle. The occlusion handling technique employed also improved the systems performance, contributing counts that would otherwise be lost. For all video samples tested, the proposed framework obtained high correct count (>93% correct counting rate) while simultaneously minimizing the false count rate. For future research, the author recommends the use of more sophisticated filters for specific sets of conditions as well as the implementation of discriminative classifier for detecting different occlusion cases.

Overlay networks have recently gained popularity as a viable alternative to overcome functionality limitations of the Internet (e.g., lack of QoS, multicast routing). They offer enhanced functionality to end-users by forming an independent and customizable virtual network over the native network. Typically, the routing at the overlay layer operates independent of that at the underlying native layer. There are several potential problems with this approach because overlay networks are selfish entities that are chiefly concerned with achieving the routing objective of their own users. This leads to complex cross-layer interactions between the native and overlay layers, and often tends to degrade the achieved performance for both layers. As overlay applications proliferate and the amount of selfish overlay traffic surges, there is a clear need for understanding the complex interactions and for strategies to manage them appropriately. Our work addresses these issues in the context of "service overlay networks", which represent virtual networks formed of persistent nodes that collaborate to offer improved services to actual end-systems. Typically, service overlays alter the route between the overlay nodes in a dynamic manner in order to satisfy a selfish objective. The objective of this thesis is to improve the stability and performance of overlay routing in this multi-layer environment. <br><br> We investigate the common problems of functionality overlap, lack of cross-layer awareness, mismatch or misalignment in routing objectives and the contention for native resources between the two layers. These problems often lead to deterioration in performance for the end-users. This thesis presents an analysis of the cross-layer interaction during fault recovery, inter-domain policy enforcement and traffic engineering in the multi-layer context. Based on our characterization of the interaction, we propose effective strategies that improve overall routing performance, with minimal side-effects on other traffic. These strategies typically 1) increase the layer-awareness (awareness of information about the other layer) at each layer, 2) introduce better control over routing dynamics and 3) offer improved overlay node placement options. Our results demonstrate how applying these strategies lead to better management of the cross-layer interaction, which in turn leads to improved routing performance for end-users.