Our study on interdomain traffic engineering focuses on AS Path Prepending (ASPP), a popular way for inbound traffic engineering. In order to improve the current situation that ISPs often practise this approach in a trial-and-error basis, we propose a greedy algorithm to help ISPs perform this approach systematically and efficiently. Then we demonstrate two fundamental issues of decentralized selfish traffic engineering, routing instability and global network performance degradation, based on an abstract model where ISPs perform traffic engineering for their individual load balance. We also present a real-world pathologic case of prepending instability from our measurement study. Some simple guidelines are given for ISPs to avoid such routing instability. / Our work on peering strategy is to help ISPs understand the economic implications of various traffic patterns and make proper decisions to optimize their business. We first conduct an economic analysis for an overlay streaming network to gain some insights on the free ride phenomenon. We further improve the analysis by taking the response of subscribers into consideration and formulate the dynamic market as a multi-leader-follower game to capture the Nash Equilibrium of the routing tussle among the major players of the Internet marketplace. Based on this framework together with a gravity traffic model, we present some important observations on the implications of overlays on ISPs' peering strategy. / Over the past several years, numerous types of "overlay" networks change the interdomain traffic pattern and ISPs lose the routing control of some interdomain traffic flows due to the application layer routing. As a result, some ISPs may provide unintended transit service for other local ISPs. It upsets the traditional business model and makes ISPs' peering strategies more complicated. / The Internet has quickly evolved into a vast global network owned and operated by thousands of interconnected Internet Service Providers. Each of these ISPs, as one autonomous system, has its individual economic interests. ISPs can achieve their objectives through peering strategy and interdomain traffic engineering. These two issues are important for ISPs' business and have significant implications on the Internet architecture. / Wang, Hui. / "September 2007." / Adviser: Dah Ming Chiu. / Source: Dissertation Abstracts International, Volume: 69-08, Section: B, page: 4865. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 163-170). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Leung Ka Hing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 94-96). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Characterization and Performance Analysis --- p.8 / Chapter 2.1 --- Two-class Proportional Differentiated Service --- p.11 / Chapter 2.2 --- N-class Proportional DS --- p.13 / Chapter 3 --- Experiments of Proportional Delay Differentiation using the It- erative Algorithm --- p.20 / Chapter 3.1 --- Experiments using Poisson arrivals --- p.21 / Chapter 3.2 --- Experiments using other arrivals distributions --- p.33 / Chapter 4 --- Dynamic Adjustment --- p.37 / Chapter 4.1 --- Adjustment algorithms --- p.37 / Chapter 5 --- Experiments of Proportional Delay Differentiation using Dy- namic Adjustment --- p.41 / Chapter 5.1 --- Illustration of dynamic adjustment --- p.43 / Chapter 5.2 --- Poisson --- p.45 / Chapter 5.3 --- Pareto --- p.48 / Chapter 5.4 --- MMPP --- p.54 / Chapter 5.5 --- Heterogeneous traffic classes --- p.60 / Chapter 5.6 --- Experiments for short time-scale analysis --- p.62 / Chapter 6 --- Multiple nodes --- p.69 / Chapter 7 --- Summary of the Experiments Results --- p.75 / Chapter 8 --- Improvement of WTP --- p.78 / Chapter 8.1 --- Algorithm --- p.78 / Chapter 8.2 --- Experiments --- p.80 / Chapter 9 --- Possible Extensions --- p.85 / Chapter 9.1 --- Application Extension --- p.85 / Chapter 9.2 --- Performance Quantification --- p.87 / Chapter 10 --- Conclusion --- p.90

Congestion on the road is identified as a severe threat to nations’ economy. To address this problem, in the past the capacity of existing infrastructure is increased by building new roads. But as history has shown, it is not only an expensive and unsustainable, but also not an efficient way of dealing with this problem. Alternatively, by identifying underutilized links, for example, in the form of parallel routes, the already existing infrastructure can often be used more efficient. This thesis focuses on the development of a framework to simulate re-routing incentives to enable an improved travel corridor performance. Thus, the effects of providing traveler information and tendering mometary incentives on a concidor’s traffic flow are investigated. The aim is to show that by changing the route choice behavior of a certain percentage of the fleet, the overall performance of the existing corridor can be increased. By using the microscopic traffic simulation tool VISSIM in combination with dynamic traffic modeling, numerous scenarios are simulated. By gradually increasing the amount of users who get access to the incentive scheme, the impacts of the penetration get analyzed as well. Based on a network stretch located in California, United States, the simulation model is developed. Using this model, three different scenarios are investigated in detail: a No Incident scenario, a Construction Work scenario and an Accident scenario. Finally, a comprehensive analysis of the simulation results takes place. It mainly focuses on the indicator travel time to discuss the impacts on the corridor performance. Interpreting the achieved simulation results, it can be stated that already small penetration rates have the potential for a significant increase of the corridor performance. To be able to optimize the corridor’s performance, free capacity on detours – especially  at bottlenecks like ramps – has to be available. Nevertheless, in case of high penetration rates, straightforward broadcasting of incentives is not an option.

Increasing demand on freeway facilities is a major challenge facing urban areas in the United States and throughout the world. Active Traffic Management (ATM) strategies can be used to increase the performance of these facilities through improved operations without the significant expenditure associated with adding capacity. One ATM strategy that has been widely deployed in the current state of practice is ramp metering, which controls the traffic demand placed on a freeway. Merge control strategies are less prevalent and largely undeveloped. This study examines the recurrently congested northbound section of Interstate Highway 35 that approaches downtown Austin, Texas. Using the VISSIM microsimulation platform, a model of this segment was developed and calibrated to reflect current peak-hour congestion. Within this model, ramp metering and merge control technologies were implemented. The impacts on traffic throughput, speed and travel time for each of these proposed systems are evaluated. / text

Urban freeway demand that frequently exceeds capacity has caused many agencies to consider many options to reduce congestion. A series of solutions that falls under the Active Traffic Management (ATM) banner have shown promising potential. Perhaps the most popular ATM strategy is ramp metering. Ramp metering involves limiting the access of vehicles to freeways at an entrance ramp. By doing this, freeway throughput, speeds, and travel time reliability can be increased, while the number of traffic incidents can be decreased. This study examines the application of an innovative ramp metering strategy, Intersection Ramp Metering (IRM), at a section of Loop 1 in Austin, TX. IRM implements the ramp metering function at the intersection immediately upstream of the entrance ramp, rather than on the ramp itself. A microsimulation analysis of this application is performed in VISSIM, and the results confirm that freeway throughput (+10%), and system average travel time (-14%), can be improved, as well as several other performance measures. / text

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published_or_final_version / Industrial and Manufacturing Systems Engineering / Master / Master of Philosophy

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Increasing air traffic and urbanisation has led to a cluttered airspace, particularly near airports, where both complex terrain and multiple moving obstacles are frequent. Accurately and efficiently predicting violations in safe separation criteria for commercial aircraft, a process called conflict detection, is therefore crucial in assessing risk associated with threats of collision. Existing avoidance systems in operation such as TCAS, EGPWS and ATC exhibit shortcomings, leaving room for uncertainty and possible conflict scenarios. A single on-board system capable of minimising errors in prediction would inform conflict resolution decisions more accurately as well as support the notion of free flight, an objective of next-generation air traffic management systems. This thesis investigates the viability of a modern algorithm, probability flow, as a method of probabilistic conflict detection for commercial aircraft in airport environments. Simulation results for realistic flight scenarios are presented in comparison with a ground-truth result obtained through Monte Carlo simulation. Observations are made regarding the suitability of probability flow for real-world application. It is found that probability flow is capable of calculating a tight upper bound to the probability of conflict quickly and accurately for most conflict scenarios. However, unreasonably large overestimates on the probability of conflict are obtained when flying parallel to an obstacle conflict region. This problem could lead to a high frequency of false alerts, particularly in aborted landing scenarios and at airports operating parallel runways. It is therefore advised that further research be conducted to resolve this problem before probability flow can be reliably implemented in an airport environment. / AFRIKAANSE OPSOMMING: Toenemende lugverkeer en verstedeliking het gelei tot ‘n deurmekaar lugruim, veral naby lughawens, waar beide komplekse terrein en verskeie bewegende struikelblokke gereeld voorkom. Akkuraat en doeltreffende voorspelling van oortredings in veilige skeidingskriteria vir kommersiële vliegtuie, naamlik konflik opsporing, is dus van kardinale belang in die beoordeling van die risiko wat verband hou met dreigemente van ‘n botsing. Bestaande vermyding stelsels in werking soos TCAS, EGPWS en ATC toon tekortkominge, wat ruimte laat vir onsekerheid en moontlike konflik scenario’s. ‘n Enkele aanboordstelsel, wat in staat is om foute in voorspelling te verminder, sou konflikresolusie besluite meer akkuraat in kennis stel, asook om die idee van vrye vlug te ondersteun, ‘n doelwit van toekomstige lugverkeer beheerstelsels. Hierdie tesis ondersoek die lewensvatbaarheid van ‘n moderne algoritme, waarskynlikheidsvloei, as ‘n metode van probabilistiese konflik opsporing vir kommersiële vliegtuie in die lughawens omgewing. Simulasie resultate vir realistiese vlug scenario’s word aangebied in vergelyking met ‘n grond-waarheid resultaat wat verkry word deur middel van Monte Carlo simulasie. Waarnemings word gemaak ten opsigte van die geskiktheid van waarskynlikheidsvloei vir die werklikheid. Dit is bevind dat waarskynlikheidsvloei in staat is om die berekening van ‘n stywe bogrens tot die waarskynlikheid van konflik vinnig en akkuraat te bepaal vir die meeste konflik scenario’s. Tog is daar ‘n onredelike groot oorskatting op die waarskynlikheid van konflik wat verkry word wanneer ‘n vliegtuig parallel met ‘n hindernis konflik streek vlieg. Hierdie probleem kan lei tot ‘n hoë frekwensie van valse waarskuwings, veral in mislukte landing scenario’s en by lughawens wat van parallel aanloopbane gebruik maak. Dit word dus aanbeveel dat verdere navorsing gedoen word om die probleem op te los voordat waarskynlikheidsvloei betroubaar in ’n lughawe omgewing geïmplementeer word.

M.Ing. / The focus of this dissertation is on the evaluation of management in traffic safety, and how it is applied, using the Road Traffic Management Corporation (RTMC) as a case study. Road Traffic Management in South Africa is in a state of crisis. The constitution provides for concurrency with respect to road traffic management, however, no mechanism has been implemented for co-operation and coordination. It has been found that the current institutional arrangements are not conducive to co-ordination and rapid interventions. Due to the scarcity of resources and the desire to streamline the institutional arrangements, an innovative model has been developed which will perform road traffic management collectively, the Road Traffic Management Corporation, RTMC. The implementation of the RTMC will require full co-operation and acceptance by all the various departments concerned, from National Government level, through to Provincial levels, and the Local Authorities. Before the Corporation can be implemented, the funding needs to be secured, and the source of the funding must be stable and committed. The implementing of such a corporation will be delicate, and organizational structure needs to be clear to all parties. At this early stage of the RTMC, the methods of management already used by the RTMC need to be compared to proper management principles, to ensure that the RTMC will have the best structure to ensure its success. Any uncertainties or concerns that may exist among those involved at lower levels can be communicated to top-level management implementing the corporation. By conducting an independent, external investigation, any short falls can be identified which may have been over looked previously. This dissertation aims to ensure that the RTMC adheres to the relevant management principles, focussing on the objective of improving road safety. A questionnaire is devised for the National Department of Transport, so that an independent view of the vision of the RTMC can be acquired. The organizational structure proposed by the RTMC is examined and evaluated to determine the relationship, communication channels, functions and responsibilities, which are intended between the various levels of management and stakeholders. The funding of a corporation such as the RTMC is considered, as the source of such funds needs to be secured before the RTMC can be implemented. A preliminary budget prepared for the RTMC is compared to what funding has been made available. The main objective of the RTMC is to improve road safety. Therefore, the process it intends to use is evaluated to determine whether the goals it intends to achieve through this process are realistic. The engineering function required to improve road safety will also be evaluated in terms of what can be done by engineers to improve the safety on South African roads.

M.Com. (Business Economics) / Please refer to full text to view abstract