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Dissertations / Theses on the topic 'Traffic design'
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Bylund, Björn, and Nicklas Blomqvist. "Design and Implementation of a Traffic Generator using Unified Traffic Modelling." Thesis, Linköpings universitet, Institutionen för datavetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-119297.
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This thesis describes the design and implementation of a traffic generator that can simulate the traffic of tens of thousands of networking devices from a given traffic model. It is designed to handle traffic models created with Unified Traffic Modelling. The traffic generator is then evaluated and different solutions are compared in an effort to find the best solution for each issue. This thesis is meant to serve as a guideline for future development of traffic generators by providing insight into the problems faced during the development of one.
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Chen, Lifeng. "RESIDENTIAL STREET DESIGN AND TRAFFIC CONTROL." The University of Arizona, 1995. http://hdl.handle.net/10150/555362.
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Lam, Wa-Kwai. "Risk analysis and traffic signal design." Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328239.
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Azimian, Amin. "Design of an Intelligent Traffic Management System." University of Dayton / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1323275800.
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Hunter, John B. Gromann Holger. "Analysis and design of a universal traffic network /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA384024.
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Thesis (M.S. in Computer Science) Naval Postgraduate School, Sept. 2000."September 2000." Thesis advisor(s): Lundy, Gilbert M. Includes bibliographical references (p. 113-115). Also available online.
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Wong, Chi-kwong, and 黃志光. "Lane-based optimization method for traffic signal design." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B31246096.
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Hunter, John B., and Holger Gromann. "Analysis and design of a universal traffic network." Thesis, Monterey, California. Naval Postgraduate School, 2000. http://hdl.handle.net/10945/9406.
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As the field of computer networking has evolved, so too has the use of these networks. Modern networks must be capable of performing more than simple data transfer. To be of value, a network must be able to handle the convergence of different types of traffic: voice, video, and data; and the Quality of Service requirements associated with each type. This thesis performs a detailed analysis of the different types of traffic, the two primary transmission media, fiber optical and copper based connections, and the connection-orientation technology to route the traffic. Presented in this thesis is a fiber-based hybrid network consisting of Asynchronous Transfer Mode at the backbone layer and Frame Relay and Passive Optical Networking at the local access layer. The proposed Universal Traffic Network, based on present-day technology, is a viable solution to the challenge imposed by the convergence of different traffic types.
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Lucio, Gilberto Flores. "Optimisation of network design for uncertain traffic matrices." Thesis, University of Essex, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413638.
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Sullivan, Andrew J. "Developing a traffic signal design manual for Alabama." Birmingham, Ala. : University of Alabama at Birmingham, 2009. https://www.mhsl.uab.edu/dt/2009m/sullivan.pdf.
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Popescu, Vlad M. "Airspace analysis and design by data aggregation and lean model synthesis." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49126.
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Air traffic demand is growing. New methods of airspace design are required that can enable new designs, do not depend on current operations, and can also support quantifiable performance goals. The main goal of this thesis is to develop methods to model inherent safety and control cost so that these can be included as principal objectives of airspace design, in support of prior work which examines capacity. The first contribution of the thesis is to demonstrate two applications of airspace analysis and design: assessing the inherent safety and control cost of the airspace. Two results are shown, a model which estimates control cost depending on autonomy allocation and traffic volume, and the characterization of inherent safety conditions which prevent unsafe trajectories. The effects of autonomy ratio and traffic volume on control cost emerge from a Monte Carlo simulation of air traffic in an airspace sector. A maximum likelihood estimation identifies the Poisson process to be the best stochastic model for control cost. Recommendations are made to support control-cost-centered airspace design. A novel method to reliably generate collision avoidance advisories, in piloted simulations, by the widely-used Traffic Alert and Collision Avoidance System (TCAS) is used to construct unsafe trajectory clusters. Results show that the inherent safety of routes can be characterized, determined, and predicted by relatively simple convex polyhedra (albeit multi-dimensional and involving spatial and kinematic information). Results also provide direct trade-off relations between spatial and kinematic constraints on route geometries that preserve safety. Accounting for these clusters thus supports safety-centered airspace design. The second contribution of the thesis is a general methodology that generalizes unifying principles from these two demonstrations. The proposed methodology has three steps: aggregate data, synthesize lean model, and guide design. The use of lean models is a result of a natural flowdown from the airspace view to the requirements. The scope of the lean model is situated at a level of granularity that identifies the macroscopic effects of operational changes on the strategic level. The lean model technique maps low-level changes to high-level properties and provides predictive results. The use of lean models allows the mapping of design variables (route geometry, autonomy allocation) to design evaluation metrics (inherent safety, control cost).
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Chen, Daizhuo. "Modeling travel time uncertainty in traffic networks." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61889.
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Thesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 147-154).
Uncertainty in travel time is one of the key factors that could allow us to understand and manage congestion in transportation networks. Models that incorporate uncertainty in travel time need to specify two mechanisms: the mechanism through which travel time uncertainty is generated and the mechanism through which travel time uncertainty influences users' behavior. Existing traffic equilibrium models are not sufficient in capturing these two mechanisms in an integrated way. This thesis proposes a new stochastic traffic equilibrium model that incorporates travel time uncertainty in an integrated manner. We focus on how uncertainty in travel time induces uncertainty in the traffic flow and vice versa. Travelers independently make probabilistic path choice decisions, inducing stochastic traffic flows in the network, which in turn result in uncertain travel times. Our model, based on the distribution of the travel time, uses the mean-variance approach in order to evaluate travelers' travel times and subsequently induce a stochastic traffic equilibrium flow pattern. In this thesis, we also examine when the new model we present has a solution as well as when the solution is unique. We discuss algorithms for solving this new model, and compare the model with existing traffic equilibrium models in the literature. We find that existing models tend to overestimate traffic flows on links with high travel time variance-to-mean ratios. To benchmark the various traffic network equilibrium models in the literature relative to the model we introduce, we investigate the total system cost, namely the total travel time in the network, for all these models. We prove three bounds that allow us to compare the system cost for the new model relative to existing models. We discuss the tightness of these bounds but also test them through numerical experimentation on test networks.
by Daizhuo Chen.
S.M.
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Anjali, Tricha. "DiffServ/MPLS Network Design and Management." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5191.
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The MultiProtocol Label Switching (MPLS) framework is used in many networks to provide efficient load balancing which distributes the traffic for efficient Quality of Service (QoS) provisioning in the network. If the MPLS framework is combined with Differentiated Services (DiffServ) architecture, together they can provide aggregate-based service differentiation and QoS. The combined use of DiffServ and MPLS in a network is called DiffServ-aware Traffic Engineering (DS-TE). Such DiffServ-based MPLS networks demand development of efficient methods for QoS provisioning. In this thesis, an automated manager for management of these DiffServ-based MPLS networks is proposed. This manager, called Traffic Engineering Automated Manager (TEAM), is a centralized authority for adaptively managing a DiffServ/MPLS domain and it is responsible for dynamic bandwidth and route management. TEAM is designed to provide a novel and unique architecture capable of managing large scale MPLS/DiffServ domains without any human interference. TEAM constantly monitors the network state and reconfigures the network for efficient handling of network events. Under the umbrella of TEAM, new schemes for Label Switched Path (LSP) setup/teardown, traffic routing, and network measurement are proposed and evaluated through simulations. Also, extensions to include Generalized MPLS (GMPLS) networks and inter-domain management are proposed.
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Dutta, Rudra. "VIRTUAL TOPOLOGY DESIGN FOR TRAFFIC GROOMING IN WDM NETWORKS." NCSU, 2001. http://www.lib.ncsu.edu/theses/available/etd-20010801-114312.
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Wavelength division multiplexing (WDM) in optical fiber networks iswidely viewed as the technology with the potential to satisfy theever-increasing bandwidth needs of network users effectively and on asustained basis.In WDM networks, nodes are equipped with optical cross-connects(OXCs), devices which can optically switch a signal on any givenwavelength from any input port to any output port.This makes it possible to establish lightpaths between any pair of network nodes.A lightpath is a clear channel in which the signal remainsin optical form throughout the physical path between the two endnodes.The set of lightpaths established over the fiberlinks defines a .Consequently, the problem arises of designing virtual topologies tooptimize a performance measure of interest for a set of trafficdemands.
With the deployment of commercial WDM systems, it has become apparentthat the cost of network components, especially line terminatingequipment (LTE) is the dominant cost in building optical networks, andis a more meaningful metric to optimize than, say, the number ofwavelengths.Furthermore, since the data rates at which each individual wavelengthoperates continue to increase (to OC-192 and beyond), it becomes clearthat a number of independent traffic components must be multiplexed inorder to efficiently utilize the wavelength capacity.These observations give rise to the concept of ,which refers to the techniques used to combine lower speed componentsonto available wavelengths in order to meet network design goals suchas cost minimization. Traffic grooming is a hard problem in generalwhich remains computationally intractable even for simple networks.
We consider the problem of traffic grooming in ring, star andtree topologies. We provide theoretical results regarding achievabilitybounds for these networks as well as practical frameworks to obtainincreasingly better feasible solutions with the expenditure of morecomputational power.
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Al-Yagout, Mohammad A. "Improving traffic characterization to enhance pavement design and performance /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/10173.
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Zhu, Keyao. "Design and analysis of traffic-groomable optical WDM networks /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2003. http://uclibs.org/PID/11984.
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Yu, Zhong McEliece Robert J. "Design issues in communications networks : reliability and traffic analysis /." Diss., Pasadena, Calif. : California Institute of Technology, 1997. http://resolver.caltech.edu/CaltechETD:etd-03192008-090303.
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Potapova, Svetlana (Svetlana S. ). "Design of long span modular bridges for traffic detours." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/53076.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009.Includes bibliographical references (leaf 53).
The oncoming large amount of bridge replacements in the next 10 to 20 years called for a detailed examination of available replacement schemes which can have variable impact on user costs. Detouring traffic with a modular bridge proved to be the most desirable scheme in terms of user costs such as traffic delays, detour distances, ultimate highway geometrics, construction crew safety, and safety of drivers. Criteria that encompassed modular bridge design were defined and two companies in North America - Acrow and Mabey - were found to provide bridges within those parameters. A brief analysis of Acrow bridges showed that maximum span lengths range in the order of 100m; this is fairly short compared to spans of many bridges that will be have to soon be replaced. The current bridge system with which modularity is achieved is a set of truss panels which are supported by abutments or piers. In order to span crossing over 100m, piers would have to be placed in the channel or on the head-slopes which is a costly and undesirable construction process. Therefore, a modular bridge which could achieve longer spans was proposed for a 2 lane and a 3 lane wide bridges using as many existing Acrow components as possible. The scheme encompasses a harp cable-stay bridge with cables spaced and sized such that they are fully interchangeable between the various bridge widths and can be built up to any span. These cables are the only additional component as the towers, the girders, and the decks are all made out of existing Acrow components.
(cont.) The pylon is balanced with an anchoring cable and ideas for modular foundations for the anchor are presented. A span of approximately 183m is possible for a 3 lane bridge limited by the maximum axial tower capacity and 250m for the 2 lane bridge based on lateral vibrations. The design fully reflects modularity and should promote the use of modular bridges for longer span crossings.
by Svetlana Potapova.
M.Eng.
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Price, Joshua. "Human factors in the design of traffic management systems." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/388155/.
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This research seeks to investigate how application of Human Factors techniques could be used to improve performance resulting from the use of technical traffic management and SCOOT validation systems. The systems used in both domains have historically been developed without consideration given to the social factors important to their use, designs instead being based solely on technical constraints. In the first stages of the project traffic management is investigated through conduction of a literature review covering the objectives, functions and constraints acting upon Traffic Management Centres (TMCs) in road, rail, maritime and air domains. Congestion management is then considered in urban road TMCs through application of the Event Analysis of Systematic Teamwork (EAST) method based on observational data collected from four TMCs, Bristol, Cardiff, Dorset and Nottingham, in which the tasks, social agents, information and relationships between these elements are considered. The EAST method is then expanded to enable investigation into TMCs’ resilience, providing further knowledge about the domain. The later stages of the project are concerned with SCOOT validation, the process by which adaptively controlled traffic lights using SCOOT are set up to reflect real traffic conditions. The domain, using the current PC SCOOT Urban Traffic Control system, is assessed through Cognitive Work Analysis (CWA) with the findings used to propose areas suitable for development. One of these areas, STOC validation, is then developed further by applying Ecological Interface Design to develop an alternative display addressing limitations with PC SCOOT’s display. This concept display is then evaluated through two empirical experiments examining performance compared to traditional displays and investigating the role of experience within the domain. Finally, by using insights obtained into the STOC validation process an automated STOC selection algorithm is developed which has the potential to redefine how STOC validation is conducted.
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Sha, Rui. "Design and performance analysis of urban traffic control systems." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10041098/.
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This study aims to investigate the design and performance of different architectures for urban traffic control with consideration of variations and uncertainties in traffic flow. The architectures, which ranging from centralised, semi-centralised to decentralised, are applied to different road networks. Both macroscopic and microscopic flow models are developed and used to calculate the performance of the systems. The macroscopic model is capable of generating essential traffic dynamics, such as traffic queues’ spillover, formation and dissipation. The control systems’ are tested under varies traffic demand levels. The results suggest that the centralised systems generally can outperform the decentralised systems, and the most benefit gained in the centralised control comes from its setting of signal offsets. On the other hand, the microscopic flow model captures the movement of each individual vehicle and drivers' rerouting behaviour with respect to traffic conditions. The test results showed that the drivers' response to the traffic condition can help a decentralised system perform as well as a centralised system. This study brings a new insight into cooperative transport management, and contributes to the state-of-the-art of urban traffic system design.
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Balcioglu, Yalcin. "Integrated V2V Wireless Network and Vehicular Traffic Simulator Design." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243957942.
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Li, Huan. "Design of Wet Surface Traffic Signal Timing Change Intervals." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/78112.
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Driver violations of traffic signals are a major cause of intersection vehicle crashes. The duration of yellow intervals is highly associated with driver yellow/red time stopping behavior. Rainy weather and wet pavement surface conditions may result in changes in both driver behavior and vehicle performance. The research presented in this thesis quantifies the impact of wet pavement surface and rainy weather conditions on driver perception-reaction times (PRTs) and deceleration levels, which are used in statistical models for the design of yellow intervals.
A new dataset with a total of 648 stop-run records were collected as part of the research effort during rainy weather and wet pavement surface conditions at the Virginia Department of Transportation's Smart Road facility. This experiment was conducted at a 72.4 km/h (45 mi/h) approach speed where participant drivers encountered a yellow indication initiation. The participant drivers were randomly selected in different age groups (under 40 years old, 40 to 59 years old, and 60 years of age or older) and genders (female and male).
Combined with an existing dataset that was collected by the same research group under clear weather conditions during the summer of 2008, statistical models for driver PRT and deceleration levels are developed, considering roadway surface and environmental parameters, driver attributes (age and gender), roadway grade, and time to the intersection at the onset of yellow. Using the state-of-the-practice procedures with the modeled PRT and deceleration levels, inclement weather yellow timings are then developed as a function of different factors (e.g., driver age/gender, roadway grade, speed limits, and precipitation levels). The results indicate that an increase in the duration of change interval is required for wet roadway surface and rainy weather conditions. Lookup tables are developed with different reliability levels to provide practical guidelines for the design of yellow signal timings in wet and rainy weather conditions. These recommended change durations can be integrated within the Vehicle Infrastructure Integration (VII) initiative to provide customizable driver warnings prior to a transition to a red indication.Master of Science
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Yang, Chun-Ming. "Enhancing driving safety through proper message design on variable message signs /." View online ; access limited to URI, 2005. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3206259.
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Sim, Samuel Wook. "An initial investigation for a monitoring program for the safety performance of design exceptions in Georgia." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45815.
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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.
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Wareing, Malcolm. "A search for an index of lift traffic performance." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293283.
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Pasias, Vasilios. "Advanced design and traffic management methods for multi-service networks." Thesis, University of Portsmouth, 2007. https://researchportal.port.ac.uk/portal/en/theses/advanced-design-and-traffic-management-methods-for-multiservice-networks(844314ef-e4d6-4bd4-9d7e-d69328093f06).html.
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This PhD thesis considers some of the more emerging problems in network modelling, namely the design of survivable hierarchical networks, Traffic Engineering (TE) and generally traffic management in survivable multi-service networks with Quality of Service (QoS) prerequisites and the planning of wireless access networks. So, in the context of the research work presented in this thesis:- Novel survivable hierarchical network design, wireless access network planning and traffic management techniques were developed. These techniques involve optimisation methods based on Linear Programming (LP) and Integer Linear Programming (ILP), as well as heuristic methods based on graph theory and computational intelligence (genetic optimisation and simulated annealing). A unified framework for off-line TE, on-line/dynamic routing and path restoration (facility restoration) that can be used in survivable multi-service QoS networks was also developed. Existing traffic management techniques were improved so that to support advanced QoS and survivability characteristics. At first, the objectives of this project are presented followed by a brief analysis of the problems encountered in the network design process. Next, the new methods for designing survivable hierarchical networks are analytically described followed by the developed wireless access network design techniques. After that, the novel traffic management methods and the aforementioned framework, developed in the context of this thesis are presented. Test results are provided together with most of the developed methods. The test results actually indicate that the developed methods can efficiently solve small, medium or even large problems, all developed methods are computationally tractable and the performance of the developed heuristic method is very close to this of the corresponding LP and ILP optimisation methods. The new heuristic methods are solved in a fraction of the time (less than 30%) that the equivalent optimisation methods are solved. Note that the specially developed design and simulation software tool NetLab was used in order to test and evaluate the new design and traffic management methods. Finally, a summary of the work carried out and the results achieved is presented followed by the conclusions and suggestions for further work.
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Stahley, Laura Margot. "Design exception in-service monitoring program development." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50399.
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When project sites consist of substandard design elements according to standards set by the Federal Highway Administration (FHWA), design exceptions are implemented. The goal of this thesis is to analyze a sample set of 18 design exceptions taken from a total of 467 design exceptions approved in Georgia from 1995 – 2012. Crash data were obtained at the locations of each of these design exceptions three years before the let date and three years after the construction end date.
To compensate for causal factors other than the design exception on the roadway, similar information from a range of control sites were also obtained. These control sites consisted of projects without design exceptions that occurred within the same time constraints as the design exception projects, were of the same work type, and were either located on the same route or within the same district. The potential safety impacts of the design exceptions were evaluated by comparing the before and after crash rates of projects before and after crash rates at these control sites
Based on these data, no statistically significant relationship between the existence of a design exception and crash rates was identified. The sample set in this study was too small and the number of crashes found at both projects with design exceptions and control sites without design exceptions was too low to perform a significant Empirical Bayesian (EB) analysis. When additional data is available, an EB before and after analysis is recommended to compensate for any potential regression to the mean bias.
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Hounsell, Nicholas Brian. "The design and performance of signal controlled intersections." Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328350.
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Yousuf, Kamran. "Time controlled network traffic shaper." Thesis, Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-2170.
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Network performance metrics such as delay variations and packet loss influence the performance of the network. As a consequence, the performance of applications on the network is also affected as most of the networked applications existing today are very much sensitive to the network performance. Therefore it is of utmost importance to test the intensity of such network level disturbances on the performance of applications. A network traffic shaper/emulator shapes the network traffic in terms of these performance metrics to test such applications in a controlled environment. Most of the traffic shapers existing today give the instantaneous step transition in delay and packet loss on network. In this work, we present time-controlled network traffic shaper, a tool that facilitates testing and experimentation of network traffic through emulation. It focuses on time variant behavior of the traffic shaper. A linear transition of delay and packet loss that is varying with respect to time may fits much better to the real network scenarios instead of an instantaneous step transition in delay and packet loss. This work illustrates the emulation capabilities of time-controlled network traffic shaper and presents its design architecture. Several approaches are analyzed to do the task and one of them is followed to develop the desired architecture of the shaper. The shaper is implemented in a small scenario and is tested to see whether the desired output is achieved or not. The shortfalls in the design of the shaper are also discussed. Results are presented that show the output from the shaper in graphical form. Although the current implementation of the shaper does not provide linear or exponential output but this can be achieved by implementing a configuration setting that is comprised of small transition values that are varying with respect to very small step sizes of time e.g. transitions on milli seconds or micro seconds. The current implementation of the shaper configuration provides the output with a transition of one milli second on every next second.kami1219@gmail.com
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Balcioglu, Yalcin. "Integrated V₂V wireless network and vehicular traffic simulator design." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1243957942.
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Destounis, Apostolos. "Traffic-Aware Resource Allocation and Feedback Design in Wireless Networks." Thesis, Supélec, 2014. http://www.theses.fr/2014SUPL0013/document.
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Les réseaux sans fil sont confrontés à une augmentation croissante en demande de données, qui devrait continuer à croitre dans les années à venir. La raison principale de cette croissance est liée à la demande en services vidéo et données. Les plus importantes approches proposées pour faire face à ce problème, notamment l'utilisation des antennes multiples, le codage OFDMA (qui font déjà partie des standards 3GPP et LTE), et le déploiement de réseaux à petites cellules, ont été examinées plutôt d’un point de vue couche physique, en se concentrant sur des mesures de performance tel que le débit total du système. Cependant, les caractéristiques du trafic vidéo et des données ainsi que les demandes individuelles des utilisateurs doivent être prises en compte pour la conception des algorithmes d'allocation de ressources radio. L'objectif de cette thèse est d'étudier l'impact des algorithmes d'allocation de ressources radio (contrôle de puissance, pré-codage, ordonnancement) ainsi que les informations concernant l’état du canal sur le comportement des files d'attente des utilisateurs. Nous étudions, en particulier, le problème de pré-codage et de contrôle de puissance dans le canal d'interférence, dans le but de réguler le comportement des files d'attente des utilisateurs et conjointement la rétroaction/estimation de canal et la sélection et ordonnancement des utilisateurs. Ceci afin d’assurer la stabilité des files d’attentes pour une grande partie des demandes de trafic dans les systèmes de diffusion MISO-OFDMA. Pour assurer cela, nous utilisons des outils mathématiques de la théorie des modèles asymptotiques "heavy traffic" et de la théorie de la stabilité stochastiqueWireless systems are facing an increase in the data demands, and this trend is expected to continue in the future. This increase is mostly due to demand of video and data services. The most prominent approaches proposed to deal with this problem, namely the use of multiple antennas and OFDMA modulations (already part of the 3GPP LTE standards) and Small Cell Networks have mostly been analyzed from a pure physical layer perspective, focusing on metrics like total system throughput. However, the traffic pattern of video and data requests as well as the individual requests of the users have to be also taken into account when designing resource allocation algorithms. The objective of this thesis is, therefore, to study the impact of physical layer resource algorithms (power control, precoding, scheduling) and CSI feedback on the behaviour of the queues of the users. In particular, we study the problems of precoding and power control to regulate the behaviour of the users' queues in the interference channel, as well as joint feedback/training and user selection and scheduling in order to stabilize the queues for a large area of traffic demands in the MISO and OFDMA broadcast channels. To this end, we use tools from heavy traffic asymptotic modelling of communication networks and stochastic stability theory
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Powale, Pallavi. "Design and testing of a roadside traffic threat alerting mechanism." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/85800.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, June 2013."May 2013." Cataloged from PDF version of thesis.
Includes bibliographical references (pages 119-122).
Every year, law enforcement officials, emergency personnel, and other workers stopped in traffic outside their vehicles are struck by inattentive drivers. Until now, most efforts to prevent these types of accidents have been geared toward making these at-risk parties more conspicuous to oncoming motorists. In contrast, this work proposes an alerting mechanism designed specifically to induce defensive behavior on the part of the at-risk officers (or other roadside personnel), once a hazardous situation has been detected. The immediate objective of this research was to produce an effective alarm prototype for a high noise, low-light operation environment such as a dimly lit highway shoulder. Based on fieldwork and background research, four such prototypes were engineered and evaluated for user response speed and subjective preference. Two of these alarm prototypes were auditory sirens and two were haptic vibrations, one placed at the waist, and one at the wrist. Haptic vibrations, which we hypothesized would be more salient in a loud and visually stimulating environment, proved to induce statistically significantly faster responses than the auditory alarms and were well received by the user community of State Police. The auditory sirens, however, were perceived as significantly more urgent than the haptic alarms and would be a beneficial addition to the haptic device to add redundancy to the system. Implemented in highway safety systems, the warning system developed through this work has the potential to help save lives.
by Pallavi Powale.
M. Eng.
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Guo, Rui. "Integrated Multi-Criteria Signal Timing Design for Sustainable Traffic Operations." Scholar Commons, 2015. https://scholarcommons.usf.edu/etd/5500.
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Traffic signal systems serve as one of the most powerful control tools in improving the efficiency of surface transportation travel. Traffic operations on arterial roads are particularly complex because of traffic interruptions caused by signalized intersections along the corridor. This dissertation research presents a systematic framework of integrated traffic control in an attempt to break down the complexities into several simpler sub-problems such as pattern recognition, environment-mobility relationships and multi-objective optimization for multi-criterial signal timing design.
The overall goal of this dissertation is to develop signal timing plans, including a day plan schedule, cycle length parameters, splits and offsets, which are suitable for real traffic conditions with consideration of multi-criterial performance of the surface transportation system. To this end, the specific objectives are to: (1) identify appropriate time-of-day breakpoints and intervals to accommodate traffic pattern variations for day plan schedule of signal timing; (2) explore the relationship between environmental outcomes (e.g., emissions) from emission estimators and mobility measures (e.g., delay and stops) for different types of intersections; (3) optimize signal timing parameters for multi-criteria objectives (e.g., minimizing vehicular delay, number of stops, marginal costs of emissions and total costs), with the comparison of performance metrics for different objectives, at the intersection level; (4) optimize arterial offsets for different objectives at the arterial level and compare the performance metrics of different objectives to recommend suitable objectives for integrated multi-criteria signal timing design in arterial traffic operations.
An extensive review of the literature, which covers existing tools, traffic patterns, traffic control with environmental concerns, and related optimization methods, shows that both opportunities and challenges have emerged for multi-criteria traffic signal timing design. These opportunities include large quantities of traffic condition data collected by system detectors or non-intrusive data collection platforms as well as powerful tools for microscopic traffic modeling and instantaneous emission estimation. The challenge is how to effectively deal with these big data, either from field collection or detailed simulation, and provide useful information for decision makers in practice. Methodologically, there's a tradeoff between the accuracy of objective function values and the computational efficiency of simulation and optimization. To address this need, in this dissertation, traffic signal timing design that systematically enables the use of integrated data and models are investigated and analyzed in the four steps/studies. The technology of identifying time-of-day breakpoints in the first study shows a mathematical way to classify dynamic traffic patterns by understanding dynamic traffic features and instabilities at a macroscopic level on arterials. Given the limitations of using built-in emissions modules within current traffic simulation and signal optimization tools, the metamodeling-based approach presented in the second study makes a methodological contribution. The findings of the second study on environment-mobility relationships set up the base for extensive application of two-stage optimization in the third and fourth studies for sustainable traffic operations and management. The comparison of outputs from an advanced estimator with those from the current tool also addresses improving the emissions module for more accurate analysis (e.g., benefit-cost analysis) in practical signal retiming projects. The third study shows that there are tradeoffs between minimizing delay and minimizing marginal costs of emissions. When total cost (including cost of delay, fuel consumption and emissions) is set as a single objective function, that objective clears the way for relatively reliable results for all the aspects. In the fourth study, the improvements in marginal cost of emissions and total cost by dynamic programming procedure are obvious, which indicates the effectiveness of using total link cost as an objective at the corridor level. In summary, this dissertation advocates a sustainable traffic control system by simultaneously considering travel time, fuel consumption and emissions. The outcomes of this integrated multi-criteria signal timing design can be easily implemented by traffic operators in their daily life of retiming signal timing.
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Deng, Yong. "Design and implementation of signaling and traffic control for AAPN." Thesis, University of Ottawa (Canada), 2007. http://hdl.handle.net/10393/27828.
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Although all-photonic network is a hot topic in recent years, most networks still do not have the ability to achieve high utilization and to allocate bandwidth dynamically and efficiently to an edge node. Many theoretical works and publications have been done in this field. However, up to now there is no commercial or lab product in this area. AAPN (Agile All-Photonic Network) is one research project focusing on these issues while at the same time avoid blocking and starvation. We designed and implemented the whole AAPN signaling protocols under Linux and produced a lab prototype under the AAPN framework. To the best of our knowledge, this is the first AAPN prototype in the world.
While bandwidth has increased so much after the Internet first came to reality, user's request increases even much faster. Congestion can not be avoided if there is no algorithm to control it. The XCP (eXplicit Control Protocol) algorithm is a promising congestion control method that uses explicit feedback. However, XCP does not work when the link capacity changes with time. In this research we designed a modified version, the XCP-CL (XCP of Cross-Layer design) algorithm, that works successfully on the AAPN network. Extensive simulation results have verified that XCP-CL has a much better performance compared to the original XCP algorithm.
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Hong, Yang. "Adaptive controller design for Internet traffic: A control theoretical approach." Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/29350.
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This thesis presents adaptive control techniques for the prevention of end-to-end traffic congestion in the Internet. Instead of using heuristics to solve the congestion problem, we have systematically applied the classical control theory in our controller design in order to always guarantee the stability of the Internet control systems, and instead of using time-domain approaches, we have employed the frequency domain techniques in our control design.
To support AQM(Active Queue Management) in the router, we have designed the adaptive P (Proportional) and the adaptive PI (Proportional-Integral) window-based router controllers for the TCP (Transmission Control Protocol) traffic. Our adaptive controllers self-tune only when significant changes in network parameters have caused the phase margin or the gain margin of the AQM control system to drift outside a specified interval.
Using the same control theoretical framework, we have provided different controllers to support best-effort streaming media traffic under different network models that we want to study. We first design an adaptive PI rate-based controller in typical network with SISO (Single-Input Single-Output) IP (Internet Protocol) routers. We then employ the DNA (Direct Nyquist Array) method to design an adaptive multi-loop PI rate-based controller under a network with MIMO (Multiple-Input Multiple-Output) IP routers.
In addition to window-based and rate-based router control algorithms, we finally design an adaptive utility-based source controller based on pole-placement technique that can provide a relatively smooth source transmission rate.
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Wan, Kam Hung. "Optimal integrated transit network design /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202002%20WAN.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002.Includes bibliographical references (leaves 92-95). Also available in electronic version. Access restricted to campus users.
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Lai, Chengdi, and 賴成迪. "Systematic design of internet congestion control : theory and algorithms." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206356.
Full textAbstract:
The Internet is dynamically shared by numerous flows of data traffic. Network congestion occurs when the aggregate flow rate persistently exceeds the network capacity, leading to excessive delivery delay and loss of user data. To control network congestion, a flow needs to adapt the sending rate to its inferred level of congestion, and a packet switch needs to report its local level of congestion.
In this framework of Internet congestion control, it is important for flows to react promptly against congestion, and robustly against interfering network events resembling congestion. This is challenging due to the highly dynamic interactions of various network components over a global scale. Prior approaches rely predominantly on empirical observations in experiments for constructing and validating designs. However, without a careful, systematic examination of all viable options, more efficient designs may be overlooked. Moreover, experimental results have limited applicability to scenarios beyond the specific experimental settings. In this thesis, I employ a novel, systematic design approach. I formalize the design process of Internet congestion control from a minimal set of empirical observations. I prove the robustness and optimality of the attained design in general settings, and validate these properties in practical experimental settings.
First, I develop a systematic method for enhancing the robustness of flows against interfering events resembling congestion. The class of additive-increase-multiplicative-decrease (AIMD) algorithms in Transmission Control Protocol (TCP) is the set of dominant algorithms governing the flow rate adaptation process. Over the present Internet, packet reordering and non-congestive loss occur frequently and are misinterpreted by TCP AIMD as packet loss due to congestion. This leads to underutilization of network resources. With a complete, formal characterization of the design space of TCP AIMD, I formulate designing wireless TCP AIMD as an optimal control problem over this space. The derived optimal algorithm attains a significant performance improvement over existing enhancements in packet-level simulation.
Second, I propose a novel design principle, known as pricing-link-by-time (PLT), that specifies how to set the measure of congestion, or “link price”, at a router to provide prompt feedback to flows. Existing feedback mechanisms require sophisticated parameter tuning, and experience drastic performance degradation with improperly tuned parameters. PLT makes parameter tuning a simple, optional process. It increases the link price as the backlog stays above a threshold value, and resets the price once the backlog goes below the threshold. I prove that such a system exhibits cyclic behavior that is robust against changes in network environment and protocol parameters. Moreover, changing the threshold value can control delay without undermining system performance. I validate these analytical results using packet-level simulation.
The incremental deployment of various enhancements have made Internet congestion control highly heterogeneous. The final part of the thesis studies this issue by analyzing the competition among flows with heterogeneous robustness against interfering network events.
While rigorous theories have been a major vehicle for understanding system designs, the thesis involves them directly in the design process. This systematic design approach can fully exploit the structural characteristics, and lead to generally applicable, effective solutions.published_or_final_version
Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy
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Ambroziak, Matt J. "Effects of pavement type on traffic noise levels." Ohio : Ohio University, 1999. http://www.ohiolink.edu/etd/view.cgi?ohiou1176229443.
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Okezue, O. G. "Design and evaluation of signal controlled highway roundabouts." Thesis, University of Bradford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376698.
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Khan, Abdul Jabbar. "A reassessment of the design of geosynthetic reinforced soil structures." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367041.
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Giesbrecht, Jeffrey Todd. "Design and implementation of an ATM traffic generation and capture card." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0028/MQ51712.pdf.
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Shelby, Steven Gebhart. "Design and evaluation of real-time adaptive traffic signal control algorithms." Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/279933.
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This dissertation investigates methods of real-time adaptive traffic signal control in the context of single isolated intersection and coordinated urban network applications. A primary goal in this dissertation is to identify and address scenarios where real-time optimized controllers do not maintain competitive performance with off-line calibrated, vehicle-actuated control techniques. An extensive literature review is supplemented by subsequent simulation experiments. Several strategies were implemented and evaluated, including OPAC, PRODYN, COP, ALLONS-D, Webster's optimized fixed-time control, and vehicle-actuated control. In particular, evaluation is based on simulation of a single, isolated intersection, where all algorithms are required to adopt the exact, deterministic traffic model used by the simulation. This approach eliminates confounding factors in comparison of algorithms, such as detector placement and disparate traffic models, focusing evaluation on the efficiency of the algorithms and their ultimate performance in terms of vehicle delay. A new algorithm is developed, employing neuro-dynamic programming techniques, also known as reinforcement learning techniques. Several very effective pruning strategies are also constructed. The final product is a very efficient algorithm capable of solving problems up to 2000 times faster than the most efficient previously published algorithm tested, with an 8% decrease in delay. This algorithm is then extended to a generalized, multi-ring control formulation. Simulation results with a standard dual-ring, eight-phase controller demonstrate that efficient, real-time solutions are achieved with a corresponding 12--22% reduction in delay relative to dual-ring, vehicle-actuated control. The real-time optimized, multi-ring controller is finally extended for urban network applications, expanding the objective function to consider downstream performance measures, and adopt standard, vehicle-actuated type coordination constraints. Control on an 8-intersection arterial is evaluated using a CORSIM simulation over a range of traffic conditions. Results are compared with TRANSYT optimized fixed-time control, coordinated vehicle-actuated control, and RHODES. Two regimes of control are revealed, where cyclic coordination constraints provide a significant benefit, and where they prevent more effective control. An adaptive coordination layer is prescribed as a unifying architecture with the potential of obtaining effective control under both regimes. The adaptive control layer specification is explicitly distinguished from existing algorithms, such as SCOOT, SCATS, and VFC-OPAC.
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Collins, Jeremy James. "Design of alphanumeric dot matrix displays for use in traffic management." Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336147.
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Bracher, Michael Todd. "Sensitivity of the 2002 pavement design guide to traffic data input." Online access for everyone, 2004. http://www.dissertations.wsu.edu/Thesis/Fall2004/m%5Fbracher%5F111804.pdf.
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Wang, Chung-Fu. "Design of a stable traffic cone /." 2006. http://adt.waikato.ac.nz/public/adt-uow20060622.161832.
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Chen, J. D., and 陳家德. "The Design of Scalable Traffic Control." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/43333516554418802262.
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碩士國立臺灣科技大學
電子工程系
87
RSVP(ReSerVation Protocol) is a popular setup protocol for resource reservation. However, The operation of RSVP at the backbone will induce a scalability problem, which is a hurdle for RSVP to evolve. In this thesis, we propose the Scalable Traffic Control (STC) architecture for RSVP to relieve the overhead in packet classification and scheduling. Moreover, to accommodate the use of STC, an aggregation scheme for RSVP control message is presented, which not only reduces the amount of state in the core router but lowers the processing overhead of RSVP control message. In general, the STC architecture is suited to be adopted in backbone to avoid the scalability problem and to provide the QoS guarantee for the real-time applications.
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Morin, Léonard Ryo. "Traffic prediction and bilevel network design." Thesis, 2020. http://hdl.handle.net/1866/24801.
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Cette thèse porte sur la modélisation du trafic dans les réseaux routiers et comment celle-ci est intégrée dans des modèles d'optimisation. Ces deux sujets ont évolué de manière plutôt disjointe: le trafic est prédit par des modèles mathématiques de plus en plus complexes, mais ce progrès n'a pas été incorporé dans les modèles de design de réseau dans lesquels les usagers de la route jouent un rôle crucial. Le but de cet ouvrage est d'intégrer des modèles d'utilités aléatoires calibrés avec de vraies données dans certains modèles biniveaux d'optimisation et ce, par une décomposition de Benders efficace. Cette décomposition particulière s'avère être généralisable par rapport à une grande classe de problèmes communs dans la litérature et permet d'en résoudre des exemples de grande taille.
Le premier article présente une méthodologie générale pour utiliser des données GPS d'une flotte de véhicules afin d'estimer les paramètres d'un modèle de demande dit recursive logit. Les traces GPS sont d'abord associées aux liens d'un réseau à l'aide d'un algorithme tenant compte de plusieurs facteurs. Les chemins formés par ces suites de liens et leurs caractéristiques sont utilisés afin d'estimer les paramètres d'un modèle de choix. Ces paramètres représentent la perception qu'ont les usagers de chacune de ces caractéristiques par rapport au choix de leur chemin. Les données utilisées dans cet article proviennent des véhicules appartenant à plusieurs compagnies de transport opérant principalement dans la région de Montréal.
Le deuxième article aborde l'intégration d'un modèle de choix de chemin avec utilités aléatoires dans une nouvelle formulation biniveau pour le problème de capture de flot de trafic. Le modèle proposé permet de représenter différents comportements des usagers par rapport à leur choix de chemin en définissant les utilités d'arcs appropriées. Ces utilités sont stochastiques ce qui contribue d'autant plus à capturer un comportement réaliste des usagers. Le modèle biniveau est rendu linéaire à travers l'ajout d'un terme lagrangien basé sur la dualité forte et ceci mène à une décomposition de Benders particulièrement efficace. Les expériences numériques sont principalement menés sur un réseau représentant la ville de Winnipeg ce qui démontre la possibilité de résoudre des problèmes de taille relativement grande.
Le troisième article démontre que l'approche du second article peut s'appliquer à une forme particulière de modèles biniveaux qui comprennent plusieurs problèmes différents. La décomposition est d'abord présentée dans un cadre général, puis dans un contexte où le second niveau du modèle biniveau est un problème de plus courts chemins. Afin d'établir que ce contexte inclut plusieurs applications, deux applications distinctes sont adaptées à la forme requise: le transport de matières dangeureuses et la capture de flot de trafic déterministe. Une troisième application, la conception et l'établissement de prix de réseau simultanés, est aussi présentée de manière similaire à l'Annexe B de cette thèse.The subject of this thesis is the modeling of traffic in road networks and its integration in optimization models. In the literature, these two topics have to a large extent evolved independently: traffic is predicted more accurately by increasingly complex mathematical models, but this progress has not been incorporated in network design models where road users play a crucial role. The goal of this work is to integrate random utility models calibrated with real data into bilevel optimization models through an efficient Benders decomposition. This particular decomposition generalizes to a wide class of problems commonly found in the literature and can be used to solved large-scale instances. The first article presents a general methodology to use GPS data gathered from a fleet of vehicles to estimate the parameters of a recursive logit demand model. The GPS traces are first matched to the arcs of a network through an algorithm taking into account various factors. The paths resulting from these sequences of arcs, along with their characteristics, are used to estimate parameters of a choice model. The parameters represent users' perception of each of these characteristics in regards to their path choice behaviour. The data used in this article comes from trucks used by a number of transportation companies operating mainly in the Montreal region. The second article addresses the integration of a random utility maximization model in a new bilevel formulation for the general flow capture problem. The proposed model allows for a representation of different user behaviors in regards to their path choice by defining appropriate arc utilities. These arc utilities are stochastic which further contributes in capturing real user behavior. This bilevel model is linearized through the inclusion of a Lagrangian term based on strong duality which paves the way for a particularly efficient Benders decomposition. The numerical experiments are mostly conducted on a network representing the city of Winnipeg which demonstrates the ability to solve problems of a relatively large size. The third article illustrates how the approach used in the second article can be generalized to a particular form of bilevel models which encompasses many different problems. The decomposition is first presented in a general setting and subsequently in a context where the lower level of the bilevel model is a shortest path problem. In order to demonstrate that this form is general, two distinct applications are adapted to fit the required form: hazmat transportation network design and general flow capture. A third application, joint network design and pricing, is also similarly explored in Appendix B of this thesis.
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Tseng, Te-En, and 曾德恩. "Lighting Design for LED Traffic Signal." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/95642126717578076642.
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碩士中州科技大學
工程技術研究所
101
ABSTRACT The lighting design for CNS 14546 LED traffic signal with the various radiation patterns LED ( θ1/10 = 20∘ ~ 120∘) is studied in this research. Four design methods by the direct lighting ,the symmetrical reflector ,the asymmetrical reflector, and the semi-reflector are adopted for the optical design. LED including various radiation patterns are, Nichia ( θ1/10 = 20∘ ), Snap LED(type HPSW-Fx & HPSW-Tx, θ1/10= 30∘ & 60∘ ), Batwing ( θ1/10 = 75∘ ), Lambertian ( θ1/10 = 90∘ ), Side Emitting ( θ1/10 = 120∘ ). The ASAP software is used for the light pattern simulation and analysis . The results show that the method is only suitable for small radiation pattern ( θ1/10 ≦ 30∘ ) LED by the direct lighting while it works for all kinds of LED by the other methods . Key words : Traffic signal, Llighting design. Optical design, Light Emitting Diode
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Hong, Jung-Sun 1976. "Children’s traffic park design in USA to promote children’s traffic safety education." Thesis, 2004. http://hdl.handle.net/2152/22375.
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Many transportation proposals aim to enhance child traffic safety, and they suggest environmental interventions, law enforcements, and educational methods as the solutions. However, educational approach has not been focusing on practices. When we consider children’s perceptual immature, hand-on education should be more efficient than verbal education. Thus, through an examination of typical child motor vehicle-related crash types in Austin and recent interviews, this Professional Report proposes a Children’s Traffic Park as a practical educational method that delivers traffic rules and influences children’s attitudes and behaviours to traffic.text
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Lin, Yi-Mu. "Simultaneous Bandwidth Allocation Design for Traffic Signal Timing Plans in Urban Grid Traffic Networks under Perfect Traffic Information." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2707200616441500.
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Lin, Yi-Mu, and 林沂穆. "Simultaneous Bandwidth Allocation Design for Traffic Signal Timing Plans in Urban Grid Traffic Networks under Perfect Traffic Information." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/70432513344242572682.
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碩士國立臺灣大學
電機工程學研究所
94
In the past, traffic signal control strategies always use the traffic patterns gathered as inputs to formulate their traffic signal timing plans. As Intelligent Transportation Systems (ITS) develop, travelers’ information may be collected through modern communication technology, and thus the types of traffic information are changed. To improve the efficient use of the possible advanced traffic information, a new real-time traffic signal control scheme, the simultaneous bandwidth allocation (SBA) design, is proposed. A future scenario with perfect traffic information for both the traffic signal controller and travelers are considered. The design of simultaneous bandwidth allocation takes the queuing vehicles at each intersection of the street as inputs, and tries to maximize the utility of the given bandwidth on a local urban grid network. Several system performance indexes (PI) are also presented to examine the performance of the bandwidth selection. The bandwidth selecting problem occurring in SBA is solved by different PI-based bandwidth selecting mechanisms. To test the feasibility of the dynamic SBA design, a simple flow changing algorithm is used to illustrate the performance of the proposed bandwidth selecting strategies. By applying different total flow rate conditions, it is found that the results of these bandwidth selecting approaches are the same once the flow rate equals or exceeds the dispersing rate of queuing vehicles. In addition, the dynamic SBA has its best performance on PIs when the incoming flow rate is equal to the dispersing rate.