This report is for the first phase of a two-phase research program to develop recommended practic... more This report is for the first phase of a two-phase research program to develop recommended practices for Georgia Department of Transportation (GDOT) for lighting rural roundabouts. Phase I of the study was designed to improve understanding of the relationship between roundabout illumination and safety, particularly in rural areas. Such information is essential to developing a sound basis for determining if a rural roundabout should, or should not, be illuminated to the current Illuminating Engineering Society (IES) standard and, if not, whether safety objectives can be met with either unlit roundabouts or roundabouts illuminated at reduced levels. The report provides a summary of relevant literature; international practices for rural roundabout illumination, a safety analysis of nighttime roundabout crashes using data from Minnesota and Georgia and provides preliminary results regarding the cost effectiveness of unlit or partially lit roundabouts as rural safety treatments.
Systematic, well-designed research provides the most effective approach to the solution of many p... more Systematic, well-designed research provides the most effective approach to the solution of many problems facing highway administrators and engineers. Often, highway problems are of local interest and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the accelerating growth of highway transportation develops increasingly complex problems of wide interest to highway authorities. These problems are best studied through a coordinated program of cooperative research. In recognition of these needs, the highway administrators of the American Association of State Highway and Transportation Officials initiated in 1962 an objective national highway research program employing modern scientific techniques. This program is supported on a continuing basis by funds from participating member states of the Association and it receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board of the National Academies was requested by the Association to administer the research program because of the Board's recognized objectivity and understanding of modern research practices. The Board is uniquely suited for this purpose as it maintains an extensive committee structure from which authorities on any highway transportation subject may be drawn; it possesses avenues of communications and cooperation with federal, state and local governmental agencies, universities, and industry; its relationship to the National Research Council is an insurance of objectivity; it maintains a full-time research correlation staff of specialists in highway transportation matters to bring the findings of research directly to those who are in a position to use them. The program is developed on the basis of research needs identified by chief administrators of the highway and transportation departments and by committees of AASHTO. Each year, specific areas of research needs to be included in the program are proposed to the National Research Council and the Board by the American Association of State Highway and Transportation Officials. Research projects to fulfill these needs are defined by the Board, and qualified research agencies are selected from those that have submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Research Council and the Transportation Research Board. The needs for highway research are many, and the National Cooperative Highway Research Program can make significant contributions to the solution of highway transportation problems of mutual concern to many responsible groups. The program, however, is intended to complement rather than to substitute for or duplicate other highway research programs.
Many Dynamic Data-Driven Application Systems (DDDAS) use replicated simulations to project possib... more Many Dynamic Data-Driven Application Systems (DDDAS) use replicated simulations to project possible future system states. In many cases there are substantial similarities among these different replications. In other cases output statistics are independent of certain simulation computations. This paper explores computational methods to exploit these properties to speed up the simulation execution time. We discuss a new algorithm to speed up the execution of replicated vehicle traffic simulations, where the output statistics of interest focus on one or more attributes such as the trajectory of a certain "target" vehicle. By focusing on correctly reproducing the behavior of the target vehicle and its interaction with other modeled entities across the different replications and modifying the event handling mechanism the execution time can be reduced. A speculative execution method using a tagging mechanism allows this speedup to occur without loss of accuracy in the output statistics.
Proceedings of the first ACM workshop on Vehicular ad hoc networks - VANET '04, 2004
There has been increasing interest in the exploitation of advances in information technology in s... more There has been increasing interest in the exploitation of advances in information technology in surface transportation systems. One trend is to exploit on-board sensing, computing and communication capabilities in vehicles, e.g., to augment and enhance existing intelligent transportation systems. A natural approach is to use vehicle-to-vehicle communications to disseminate information. In this paper, we propose MDDV, a mobility-centric approach for data dissemination in vehicular networks designed to operate efficiently and reliably despite the highly mobile, partitioned nature of these networks. MDDV is designed to exploit vehicle mobility for data dissemination, and combines the idea of opportunistic forwarding, trajectory based forwarding and geographical forwarding. We develop a generic mobile computing approach for designing localized algorithms in vehicular networks. Vehicles perform local operations based on their own knowledge while they collectively achieve a global behavior. We evaluate the performance of the MDDV algorithm using realistic simulation of the vehicle traffic in Atlanta area.
Proceedings of the Winter Simulation Conference 2014, 2014
We propose a data structure that stores previously observed vehicle paths in a given area in orde... more We propose a data structure that stores previously observed vehicle paths in a given area in order to predict the forward trajectory of an observed vehicle at any stage. Incomplete vehicle trajectories are conditioned against in a Past Tree, to predict future trajectories in another tree structure-a Future Tree. Many use cases in transportation simulation benefit from higher validity by considering historical paths in determining how to route vehicle entities. Instead of assigning static and independent turn probabilities at intersections, the storage and retrieval of historical path information can give a more accurate picture of future traffic trends and enhance the capabilities of real-time simulations to, say, inform mobile phone users of expected traffic jams along certain segments, direct the search efforts of law enforcement personnel, or allow more effective synchronization of traffic signals.
Proceedings of the 2009 Winter Simulation Conference (WSC), 2009
Traffic congestion is a source of significant economic and social costs in urban areas. Intellige... more Traffic congestion is a source of significant economic and social costs in urban areas. Intelligent Transportation Systems (ITS) are a promising means to help alleviate congestion by utilizing advanced sensing, computing, and communication technologies. This paper investigates a basic ITS framework-Advanced Traveler Information System (ATIS)-using wireless vehicle-to-vehicle and vehicle-to-roadside communication and assuming an ideal communication environment. Utilizing an off-the-shelf microscopic simulation model this paper explores both a centralized (CA) and decentralized (DCA) ATIS architecture. Results of this study indicate that an ATIS using wireless communication can save travel time given varying combinations of system characteristics: traffic flow, communication radio range, and penetration ratio. Challenges are also noted in relying solely on instrumented vehicle data in an ATIS implementation.
Ad hoc distributed simulation, a methodology for embedded online simulation, has been studied for... more Ad hoc distributed simulation, a methodology for embedded online simulation, has been studied for the steady-state simulation of open queueing networks. However, for most online simulation applications, the capability of a simulation approach to respond to system dynamics is at least as important as the performance in steady-state analysis. Hence, this paper focuses on the prediction accuracy of the ad hoc approach in open queueing networks with short-term system-state transients. We empirically demonstrate that, with slight modification to the prior ad hoc approach for steady-state studies, system dynamics can be modeled appropriately. Furthermore, a potential livelock issue that arises with the modification is addressed.
Congestion is one of the major issues facing today's transportation sector. Recent efforts have b... more Congestion is one of the major issues facing today's transportation sector. Recent efforts have been geared toward providing traffic information to travelers, to facilitate better travel decisions, and transportation facility managers, to allow them to better manage traffic operations. Currently, real-time traffic information is primarily limited to freeways and a small subset of major arterials. This research effort explores the feasibility of an online data-driven simulation based methodology to address the lack of real-time arterial performance measures. The core of this methodology is the development of an online simulation tool that relies on commonly available arterial point sensor data, such as that from loop detectors or video cameras. Preliminary analysis indicates that the approach being considered is feasible as a model of the "real-world" was capable of reflecting performance measures with relatively high levels of accuracy. Limitations of the current research design and more immediate future directions are also presented.
Current research in applying the Dynamic Data Driven Application Systems (DDDAS) concept to monit... more Current research in applying the Dynamic Data Driven Application Systems (DDDAS) concept to monitor and manage surface transportation systems in day-today and emergency scenarios is described. This work is focused in four, tightly coupled areas. First, a novel approach to predicting future system states termed ad hoc distributed simulations has been developed and is under investigation. Second, on-line simulation models that can incorporate real-time data and perform rollback operations for optimistic ad hoc distributed simulations are being developed and configured with data corresponding to the Atlanta metropolitan area. Third, research in the analysis of real-time data is being used to define approaches for transportation system data collection that can drive distributed on-line simulations. Finally, research in data dissemination approaches is examining effective means to distribute information in mobile distributed systems to support the ad hoc distributed simulation concept.
Proceedings of the 2003 International Conference on Machine Learning and Cybernetics (IEEE Cat. No.03EX693)
Simulation has been utilized in the planning and development of almost all sectors of the transpo... more Simulation has been utilized in the planning and development of almost all sectors of the transportation field. The practicing transportation community primarily relies on simulation packages, as opposed to "ground up" simulation development. Unfortunately, the use of these simulation packages has several disadvantages, most notably the "black box" phenomenon and reduced modeling flexibility. The simulation approach described in this paper lays the foundation for a transportation simulation approach that minimizes the "black box" problem and increases modeling flexibility, while still providing an easy to use package in which highly capable models may be quickly and accurately built. This simulation approach utilizes SIMAN and ARENA. This paper includes a brief discussion of the simulation approach, a comparison of the proposed simulation and CORSIM simulation results for an intersection and an arterial, and a comparison of the proposed simulation control delay to delays collected for a twelve intersection grid north of downtown Chicago.
Proceedings of the 2011 Winter Simulation Conference (WSC), 2011
An ad hoc distributed simulation is a collection of online simulators embedded in a sensor networ... more An ad hoc distributed simulation is a collection of online simulators embedded in a sensor network that communicate and synchronize among themselves. Each simulator is driven by sensor data and state predictions from other simulators. Previous work has examined this approach in transportation systems and queueing networks. Ad hoc distributed simulations have the potential to offer greater resilience to failures, but also raise a variety of statistical issues including: (a) rapid and effective estimation of the input processes at modeling boundaries; (b) estimation of system-wide performance measures from individual simulator outputs; and (c) correction mechanisms responding to unexpected events or inaccuracies of the model itself. This paper formalizes these problems and discusses relevant statistical methodologies that allow ad hoc distributed simulations to realize their full potential. To illustrate one aspect of these methodologies, an example concerning rollback threshold parameter selection is presented in the context of managing surface transportation systems.
Proceedings of the 2011 Winter Simulation Conference (WSC), 2011
Interest management is essential for reducing communication overhead by filtering irrelevant mess... more Interest management is essential for reducing communication overhead by filtering irrelevant messages in mobile distributed systems. Interest management schemes developed for distributed simulation systems such as those based on HLA can be applied to mobile systems. Sort-based schemes have been proposed and shown to yield good performance. When using sort-based schemes in mobile peer-to-peer systems, questions such as the design of the sorting mechanism and where to perform the sorting process must be addressed. This paper proposes an interest management mechanism for mobile peer-to-peer systems, that divides the entire space into cells and uses a bucket sort to sort the regions in each cell. A mobile landmarking scheme is presented to implement this scheme in mobile peer-to-peer systems. The new mechanism is expected to have better computational efficiency for both static and dynamic matching. Experimental results indicate that this approach yields better performance than several alternate interest management schemes.
Proceedings of the 2006 Winter Simulation Conference, 2006
Widespread deployment of sensors in roadways and vehicles is creating new challenges in effective... more Widespread deployment of sensors in roadways and vehicles is creating new challenges in effectively exploiting the wealth of real-time transportation system data. However, the precision of the real-time data varies depending on the level of data aggregation. For example, minute-by-minute data are more precise than hourly average data. This paper explores the ability to create an accurate estimate of the evolving state of transportation systems using real-time roadway data aggregated at various update intervals. It is found that simulation based on inflow data aggregated over a short time interval is capable of providing a superior representation of the real world over longer aggregate intervals. However, the perceived improvements are minimal under congested conditions and most pronounced under un-congested conditions. In addition, outflow constraints should be considered during congested flow periods, otherwise significant deviation from the real world performance may arise.
Proceedings Title: Proceedings of the 2012 Winter Simulation Conference (WSC), 2012
Despite recent technological advancements in alleviating roadway congestion, there is still a con... more Despite recent technological advancements in alleviating roadway congestion, there is still a considerable amount of time and fuel wasted by travelers. In searching for solutions to mitigate congestion, a number of research efforts have been geared toward developing simulation tools to provide real-time performance measures. One of the challenges of such tools is that the underlying simulation model does not always adequately reflect field conditions outside of the time period for which it was calibrated. In this paper, this is highlighted when calibrating a model for two different periods. During this exercise, 1000 model replicates were generated to explore the sensitivity of potential calibration parameter values. From this analysis only one replicate was found to be adequately calibrated for both periods. This paper suggests that a real-time calibration algorithm should be included in online, data-driven microscopic traffic simulation tools.
Proceedings of the 2009 Winter Simulation Conference (WSC), 2009
A testbed for evaluation of online distributed simulations of transportation system infrastructur... more A testbed for evaluation of online distributed simulations of transportation system infrastructures is described that includes a modest portion of an urban road network in the midtown region of Atlanta, Georgia. The testbed includes sensors, servers, wireless communications, and mobile transportation simulations configured to model the testbed region. The system architecture for this testbed is described. Results of experiments evaluating wireless communication performance are presented. An implementation of an online traffic simulation based on a commercial simulator was developed, and results comparing the system's predictive accuracy with observed travel times through the simulated region are presented to illustrate a typical use of the testbed and to identify certain requirements for achieving reliable travel time predictions using online simulations.
Tracking the movement of vehicles in urban environments using fixed position sensors, mobile sens... more Tracking the movement of vehicles in urban environments using fixed position sensors, mobile sensors, and crowd-sourced data is a challenging but important problem in applications such as law enforcement and defense. A dynamic data driven application system (DDDAS) is described to track a vehicle's movements by repeatedly identifying the vehicle under investigation from live image and video data, predicting probable future locations, and repositioning sensors or retargeting requests for information in order to reacquire the vehicle. An overview of the envisioned system is described that includes image processing algorithms to detect and recapture the vehicle from live image data, a computational framework to predict probable vehicle locations at future points in time, and a power aware data distribution management system to disseminate data and requests for information over ad hoc wireless communication networks. A testbed under development in the midtown area of Atlanta, Georgia in the United States is briefly described.
Proceedings of the 2010 Winter Simulation Conference, 2010
Transportation professionals are increasingly exploring multi-pronged solutions to alleviate traf... more Transportation professionals are increasingly exploring multi-pronged solutions to alleviate traffic congestion. Real-time information systems for travelers and facility managers are one approach that has been the focus of many recent efforts. Real-time performance information can facilitate more efficient roadway usage and operations. Toward this end, a dynamic data driven simulation based system for estimating and predicting performance measures along arterial streets in real-time is described that uses microscopic traffic simulations, driven by point sensor data. Current practices of real-time estimation of roadway performance measures are reviewed. The proposed real-time data driven arterial simulation methodology to estimate performance measures along arterials is presented as well as preliminary field results that provide evidence to validate this approach.
Freeway operating conditions are typically evaluated using the level of service (LOS) concept, wh... more Freeway operating conditions are typically evaluated using the level of service (LOS) concept, which is defined according to the macroscopic traffic parameter, density. Although traffic density may provide general estimates of current traffic conditions, this parameter generally fails to communicate the variability in the quality of traffic flow experienced by individual drivers. This variability may be caused by factors that are not effectively being captured by density, such as travel lane, vehicle position within a platoon, characteristics of roadway geometry, etc. This paper investigates the variability of traffic flow quality as indicated by measurements of speed and acceleration noise (standard deviation of acceleration) using field data obtained from instrumented vehicles equipped with global positioning system (GPS) devices. The microscopic measures observed from individual vehicles are compared with density-based LOS, which are calculated with data from the Atlanta, GA traffic monitoring system. This comparison reveals that under the same LOS condition, drivers may experience significant differences in the quality of traffic flow. In addition, the comparison indicates that drivers under different density based LOS conditions may experience a similar level of traffic flow quality. The variability generally becomes larger as traffic conditions worsen.
Transportation Research Record: Journal of the Transportation Research Board, 2008
Previous research efforts have quantified the capacity of non-barrier-separated, high-occupancy v... more Previous research efforts have quantified the capacity of non-barrier-separated, high-occupancy vehicle (HOV) lanes. However, the majority of these efforts have focused on HOV lanes that usually operate well below capacity. In contrast, the I-85 HOV lanes in Atlanta, Georgia, usually operate under constrained flow conditions during morning and afternoon peak periods. This provides an opportunity to assess the relative performance of the HOV lane to the adjacent general-purpose (GP) lanes, which also undergo constrained flow conditions. This paper considers the relationship between the performance of the HOV and GP lanes by examining speed differential effects as a function of congestion on GP lanes. The research provides evidence of a sympathetic reduction in vehicle speeds in the HOV lane. This is likely explained by the safety concerns of the HOV drivers associated with the potential for vehicles using the congested GP lanes to enter the HOV lane, as well as the safety concerns of...
This report is for the first phase of a two-phase research program to develop recommended practic... more This report is for the first phase of a two-phase research program to develop recommended practices for Georgia Department of Transportation (GDOT) for lighting rural roundabouts. Phase I of the study was designed to improve understanding of the relationship between roundabout illumination and safety, particularly in rural areas. Such information is essential to developing a sound basis for determining if a rural roundabout should, or should not, be illuminated to the current Illuminating Engineering Society (IES) standard and, if not, whether safety objectives can be met with either unlit roundabouts or roundabouts illuminated at reduced levels. The report provides a summary of relevant literature; international practices for rural roundabout illumination, a safety analysis of nighttime roundabout crashes using data from Minnesota and Georgia and provides preliminary results regarding the cost effectiveness of unlit or partially lit roundabouts as rural safety treatments.
Systematic, well-designed research provides the most effective approach to the solution of many p... more Systematic, well-designed research provides the most effective approach to the solution of many problems facing highway administrators and engineers. Often, highway problems are of local interest and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the accelerating growth of highway transportation develops increasingly complex problems of wide interest to highway authorities. These problems are best studied through a coordinated program of cooperative research. In recognition of these needs, the highway administrators of the American Association of State Highway and Transportation Officials initiated in 1962 an objective national highway research program employing modern scientific techniques. This program is supported on a continuing basis by funds from participating member states of the Association and it receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board of the National Academies was requested by the Association to administer the research program because of the Board's recognized objectivity and understanding of modern research practices. The Board is uniquely suited for this purpose as it maintains an extensive committee structure from which authorities on any highway transportation subject may be drawn; it possesses avenues of communications and cooperation with federal, state and local governmental agencies, universities, and industry; its relationship to the National Research Council is an insurance of objectivity; it maintains a full-time research correlation staff of specialists in highway transportation matters to bring the findings of research directly to those who are in a position to use them. The program is developed on the basis of research needs identified by chief administrators of the highway and transportation departments and by committees of AASHTO. Each year, specific areas of research needs to be included in the program are proposed to the National Research Council and the Board by the American Association of State Highway and Transportation Officials. Research projects to fulfill these needs are defined by the Board, and qualified research agencies are selected from those that have submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Research Council and the Transportation Research Board. The needs for highway research are many, and the National Cooperative Highway Research Program can make significant contributions to the solution of highway transportation problems of mutual concern to many responsible groups. The program, however, is intended to complement rather than to substitute for or duplicate other highway research programs.
Many Dynamic Data-Driven Application Systems (DDDAS) use replicated simulations to project possib... more Many Dynamic Data-Driven Application Systems (DDDAS) use replicated simulations to project possible future system states. In many cases there are substantial similarities among these different replications. In other cases output statistics are independent of certain simulation computations. This paper explores computational methods to exploit these properties to speed up the simulation execution time. We discuss a new algorithm to speed up the execution of replicated vehicle traffic simulations, where the output statistics of interest focus on one or more attributes such as the trajectory of a certain "target" vehicle. By focusing on correctly reproducing the behavior of the target vehicle and its interaction with other modeled entities across the different replications and modifying the event handling mechanism the execution time can be reduced. A speculative execution method using a tagging mechanism allows this speedup to occur without loss of accuracy in the output statistics.
Proceedings of the first ACM workshop on Vehicular ad hoc networks - VANET '04, 2004
There has been increasing interest in the exploitation of advances in information technology in s... more There has been increasing interest in the exploitation of advances in information technology in surface transportation systems. One trend is to exploit on-board sensing, computing and communication capabilities in vehicles, e.g., to augment and enhance existing intelligent transportation systems. A natural approach is to use vehicle-to-vehicle communications to disseminate information. In this paper, we propose MDDV, a mobility-centric approach for data dissemination in vehicular networks designed to operate efficiently and reliably despite the highly mobile, partitioned nature of these networks. MDDV is designed to exploit vehicle mobility for data dissemination, and combines the idea of opportunistic forwarding, trajectory based forwarding and geographical forwarding. We develop a generic mobile computing approach for designing localized algorithms in vehicular networks. Vehicles perform local operations based on their own knowledge while they collectively achieve a global behavior. We evaluate the performance of the MDDV algorithm using realistic simulation of the vehicle traffic in Atlanta area.
Proceedings of the Winter Simulation Conference 2014, 2014
We propose a data structure that stores previously observed vehicle paths in a given area in orde... more We propose a data structure that stores previously observed vehicle paths in a given area in order to predict the forward trajectory of an observed vehicle at any stage. Incomplete vehicle trajectories are conditioned against in a Past Tree, to predict future trajectories in another tree structure-a Future Tree. Many use cases in transportation simulation benefit from higher validity by considering historical paths in determining how to route vehicle entities. Instead of assigning static and independent turn probabilities at intersections, the storage and retrieval of historical path information can give a more accurate picture of future traffic trends and enhance the capabilities of real-time simulations to, say, inform mobile phone users of expected traffic jams along certain segments, direct the search efforts of law enforcement personnel, or allow more effective synchronization of traffic signals.
Proceedings of the 2009 Winter Simulation Conference (WSC), 2009
Traffic congestion is a source of significant economic and social costs in urban areas. Intellige... more Traffic congestion is a source of significant economic and social costs in urban areas. Intelligent Transportation Systems (ITS) are a promising means to help alleviate congestion by utilizing advanced sensing, computing, and communication technologies. This paper investigates a basic ITS framework-Advanced Traveler Information System (ATIS)-using wireless vehicle-to-vehicle and vehicle-to-roadside communication and assuming an ideal communication environment. Utilizing an off-the-shelf microscopic simulation model this paper explores both a centralized (CA) and decentralized (DCA) ATIS architecture. Results of this study indicate that an ATIS using wireless communication can save travel time given varying combinations of system characteristics: traffic flow, communication radio range, and penetration ratio. Challenges are also noted in relying solely on instrumented vehicle data in an ATIS implementation.
Ad hoc distributed simulation, a methodology for embedded online simulation, has been studied for... more Ad hoc distributed simulation, a methodology for embedded online simulation, has been studied for the steady-state simulation of open queueing networks. However, for most online simulation applications, the capability of a simulation approach to respond to system dynamics is at least as important as the performance in steady-state analysis. Hence, this paper focuses on the prediction accuracy of the ad hoc approach in open queueing networks with short-term system-state transients. We empirically demonstrate that, with slight modification to the prior ad hoc approach for steady-state studies, system dynamics can be modeled appropriately. Furthermore, a potential livelock issue that arises with the modification is addressed.
Congestion is one of the major issues facing today's transportation sector. Recent efforts have b... more Congestion is one of the major issues facing today's transportation sector. Recent efforts have been geared toward providing traffic information to travelers, to facilitate better travel decisions, and transportation facility managers, to allow them to better manage traffic operations. Currently, real-time traffic information is primarily limited to freeways and a small subset of major arterials. This research effort explores the feasibility of an online data-driven simulation based methodology to address the lack of real-time arterial performance measures. The core of this methodology is the development of an online simulation tool that relies on commonly available arterial point sensor data, such as that from loop detectors or video cameras. Preliminary analysis indicates that the approach being considered is feasible as a model of the "real-world" was capable of reflecting performance measures with relatively high levels of accuracy. Limitations of the current research design and more immediate future directions are also presented.
Current research in applying the Dynamic Data Driven Application Systems (DDDAS) concept to monit... more Current research in applying the Dynamic Data Driven Application Systems (DDDAS) concept to monitor and manage surface transportation systems in day-today and emergency scenarios is described. This work is focused in four, tightly coupled areas. First, a novel approach to predicting future system states termed ad hoc distributed simulations has been developed and is under investigation. Second, on-line simulation models that can incorporate real-time data and perform rollback operations for optimistic ad hoc distributed simulations are being developed and configured with data corresponding to the Atlanta metropolitan area. Third, research in the analysis of real-time data is being used to define approaches for transportation system data collection that can drive distributed on-line simulations. Finally, research in data dissemination approaches is examining effective means to distribute information in mobile distributed systems to support the ad hoc distributed simulation concept.
Proceedings of the 2003 International Conference on Machine Learning and Cybernetics (IEEE Cat. No.03EX693)
Simulation has been utilized in the planning and development of almost all sectors of the transpo... more Simulation has been utilized in the planning and development of almost all sectors of the transportation field. The practicing transportation community primarily relies on simulation packages, as opposed to "ground up" simulation development. Unfortunately, the use of these simulation packages has several disadvantages, most notably the "black box" phenomenon and reduced modeling flexibility. The simulation approach described in this paper lays the foundation for a transportation simulation approach that minimizes the "black box" problem and increases modeling flexibility, while still providing an easy to use package in which highly capable models may be quickly and accurately built. This simulation approach utilizes SIMAN and ARENA. This paper includes a brief discussion of the simulation approach, a comparison of the proposed simulation and CORSIM simulation results for an intersection and an arterial, and a comparison of the proposed simulation control delay to delays collected for a twelve intersection grid north of downtown Chicago.
Proceedings of the 2011 Winter Simulation Conference (WSC), 2011
An ad hoc distributed simulation is a collection of online simulators embedded in a sensor networ... more An ad hoc distributed simulation is a collection of online simulators embedded in a sensor network that communicate and synchronize among themselves. Each simulator is driven by sensor data and state predictions from other simulators. Previous work has examined this approach in transportation systems and queueing networks. Ad hoc distributed simulations have the potential to offer greater resilience to failures, but also raise a variety of statistical issues including: (a) rapid and effective estimation of the input processes at modeling boundaries; (b) estimation of system-wide performance measures from individual simulator outputs; and (c) correction mechanisms responding to unexpected events or inaccuracies of the model itself. This paper formalizes these problems and discusses relevant statistical methodologies that allow ad hoc distributed simulations to realize their full potential. To illustrate one aspect of these methodologies, an example concerning rollback threshold parameter selection is presented in the context of managing surface transportation systems.
Proceedings of the 2011 Winter Simulation Conference (WSC), 2011
Interest management is essential for reducing communication overhead by filtering irrelevant mess... more Interest management is essential for reducing communication overhead by filtering irrelevant messages in mobile distributed systems. Interest management schemes developed for distributed simulation systems such as those based on HLA can be applied to mobile systems. Sort-based schemes have been proposed and shown to yield good performance. When using sort-based schemes in mobile peer-to-peer systems, questions such as the design of the sorting mechanism and where to perform the sorting process must be addressed. This paper proposes an interest management mechanism for mobile peer-to-peer systems, that divides the entire space into cells and uses a bucket sort to sort the regions in each cell. A mobile landmarking scheme is presented to implement this scheme in mobile peer-to-peer systems. The new mechanism is expected to have better computational efficiency for both static and dynamic matching. Experimental results indicate that this approach yields better performance than several alternate interest management schemes.
Proceedings of the 2006 Winter Simulation Conference, 2006
Widespread deployment of sensors in roadways and vehicles is creating new challenges in effective... more Widespread deployment of sensors in roadways and vehicles is creating new challenges in effectively exploiting the wealth of real-time transportation system data. However, the precision of the real-time data varies depending on the level of data aggregation. For example, minute-by-minute data are more precise than hourly average data. This paper explores the ability to create an accurate estimate of the evolving state of transportation systems using real-time roadway data aggregated at various update intervals. It is found that simulation based on inflow data aggregated over a short time interval is capable of providing a superior representation of the real world over longer aggregate intervals. However, the perceived improvements are minimal under congested conditions and most pronounced under un-congested conditions. In addition, outflow constraints should be considered during congested flow periods, otherwise significant deviation from the real world performance may arise.
Proceedings Title: Proceedings of the 2012 Winter Simulation Conference (WSC), 2012
Despite recent technological advancements in alleviating roadway congestion, there is still a con... more Despite recent technological advancements in alleviating roadway congestion, there is still a considerable amount of time and fuel wasted by travelers. In searching for solutions to mitigate congestion, a number of research efforts have been geared toward developing simulation tools to provide real-time performance measures. One of the challenges of such tools is that the underlying simulation model does not always adequately reflect field conditions outside of the time period for which it was calibrated. In this paper, this is highlighted when calibrating a model for two different periods. During this exercise, 1000 model replicates were generated to explore the sensitivity of potential calibration parameter values. From this analysis only one replicate was found to be adequately calibrated for both periods. This paper suggests that a real-time calibration algorithm should be included in online, data-driven microscopic traffic simulation tools.
Proceedings of the 2009 Winter Simulation Conference (WSC), 2009
A testbed for evaluation of online distributed simulations of transportation system infrastructur... more A testbed for evaluation of online distributed simulations of transportation system infrastructures is described that includes a modest portion of an urban road network in the midtown region of Atlanta, Georgia. The testbed includes sensors, servers, wireless communications, and mobile transportation simulations configured to model the testbed region. The system architecture for this testbed is described. Results of experiments evaluating wireless communication performance are presented. An implementation of an online traffic simulation based on a commercial simulator was developed, and results comparing the system's predictive accuracy with observed travel times through the simulated region are presented to illustrate a typical use of the testbed and to identify certain requirements for achieving reliable travel time predictions using online simulations.
Tracking the movement of vehicles in urban environments using fixed position sensors, mobile sens... more Tracking the movement of vehicles in urban environments using fixed position sensors, mobile sensors, and crowd-sourced data is a challenging but important problem in applications such as law enforcement and defense. A dynamic data driven application system (DDDAS) is described to track a vehicle's movements by repeatedly identifying the vehicle under investigation from live image and video data, predicting probable future locations, and repositioning sensors or retargeting requests for information in order to reacquire the vehicle. An overview of the envisioned system is described that includes image processing algorithms to detect and recapture the vehicle from live image data, a computational framework to predict probable vehicle locations at future points in time, and a power aware data distribution management system to disseminate data and requests for information over ad hoc wireless communication networks. A testbed under development in the midtown area of Atlanta, Georgia in the United States is briefly described.
Proceedings of the 2010 Winter Simulation Conference, 2010
Transportation professionals are increasingly exploring multi-pronged solutions to alleviate traf... more Transportation professionals are increasingly exploring multi-pronged solutions to alleviate traffic congestion. Real-time information systems for travelers and facility managers are one approach that has been the focus of many recent efforts. Real-time performance information can facilitate more efficient roadway usage and operations. Toward this end, a dynamic data driven simulation based system for estimating and predicting performance measures along arterial streets in real-time is described that uses microscopic traffic simulations, driven by point sensor data. Current practices of real-time estimation of roadway performance measures are reviewed. The proposed real-time data driven arterial simulation methodology to estimate performance measures along arterials is presented as well as preliminary field results that provide evidence to validate this approach.
Freeway operating conditions are typically evaluated using the level of service (LOS) concept, wh... more Freeway operating conditions are typically evaluated using the level of service (LOS) concept, which is defined according to the macroscopic traffic parameter, density. Although traffic density may provide general estimates of current traffic conditions, this parameter generally fails to communicate the variability in the quality of traffic flow experienced by individual drivers. This variability may be caused by factors that are not effectively being captured by density, such as travel lane, vehicle position within a platoon, characteristics of roadway geometry, etc. This paper investigates the variability of traffic flow quality as indicated by measurements of speed and acceleration noise (standard deviation of acceleration) using field data obtained from instrumented vehicles equipped with global positioning system (GPS) devices. The microscopic measures observed from individual vehicles are compared with density-based LOS, which are calculated with data from the Atlanta, GA traffic monitoring system. This comparison reveals that under the same LOS condition, drivers may experience significant differences in the quality of traffic flow. In addition, the comparison indicates that drivers under different density based LOS conditions may experience a similar level of traffic flow quality. The variability generally becomes larger as traffic conditions worsen.
Transportation Research Record: Journal of the Transportation Research Board, 2008
Previous research efforts have quantified the capacity of non-barrier-separated, high-occupancy v... more Previous research efforts have quantified the capacity of non-barrier-separated, high-occupancy vehicle (HOV) lanes. However, the majority of these efforts have focused on HOV lanes that usually operate well below capacity. In contrast, the I-85 HOV lanes in Atlanta, Georgia, usually operate under constrained flow conditions during morning and afternoon peak periods. This provides an opportunity to assess the relative performance of the HOV lane to the adjacent general-purpose (GP) lanes, which also undergo constrained flow conditions. This paper considers the relationship between the performance of the HOV and GP lanes by examining speed differential effects as a function of congestion on GP lanes. The research provides evidence of a sympathetic reduction in vehicle speeds in the HOV lane. This is likely explained by the safety concerns of the HOV drivers associated with the potential for vehicles using the congested GP lanes to enter the HOV lane, as well as the safety concerns of...
Uploads
Papers by Michael Hunter