- Email: [email protected]
Direct ramp metering in hierarchical control of freeway systems
Recent doctoral dissertations equation developed in this research provides an estimate for the k value. The equation is expressed as a function of the degree of saturation. A separate equation was developed for each signal controller type. Results show that the proposed k variables provide delay estimates closer to the measured delay when compared to delay estimates using a fixed k value of 0.5. The study also developed alternative factors to account for the early/ late arrival of the platoon at the intersection. A separate factor is provided for each arrival type and for a broad range of platoon arrival conditions.
An analysis of the effectiveness of high-occupancy vehicle lanes. Dahlgren, Joy Wilbrand, Ph.D. University of California, Berkeley, 1994. 186 pp. Chair: Adib Kanafani. Order Number DA9529279 The success of a high occupancy vehicle (HOV) lane in motivating people to shift to HOVs depends on maintaining a travel time differential between it and the adjacent general purpose lanes. This differential exists only if there is continuing delay on the general purpose lanes. Therefore, it is not clear that construction of an HOV lane will always reduce delay more than construction of a general purpose lane. The objective of this research is to determine the circumstances in which this would be the case. The hypothesis is that such circumstances would be quite limited, and this proves to be the case. The intended benefits of HOV lanes are defined as reduced person-delay and reduced emissions. A model is developed to calculate these benefits for four alternatives: add an HOV lane, add a general purpose lane, convert an existing lane to an HOV lane, and do nothing. Application of the model in typical situations shows that with initial delays on the order of 15 minutes or more, adding an HOV lane would provide substantial reductions in delay and some reduction in emissions. However, in a wide range of such situations, adding a general purpose lane would be even more effective. Only if the initial delay is long and the proportion of HOVs falls in a rather narrow range would an added HOV lane be more effective. The proportion of HOVs must be such that it allows good utilization of the HOV lane while maintaining a sufficient travel time dif? erential to motivate a shift to HOVs. Adding an HOV lane to a three lane freeway will be more effective than adding a general purpose lane only if the initial maximum delay is on the order of 35 minutes or more and the proportion of HOVs is on the order of 20%. Federal policies encourage construction of HOV lanes and do not provide funding for general purpose lanes in areas that have not attained air quality standards. The findings of this research suggest a need to reconsider these policies.
Analytical and simulation models of weaving area operations under non-freeway conditions. Iqbal, Muhammad Shahid. Ph.D. New Jersey Institute of
13
Technology, 1994. 280 pp. Adviser: Athanassios K. Bladikas. Order Numkr DA9514444 This research presents a state-of-the-art analytical approach and simulation models for the analysis of the level of service and operation of non-freeway weaving areas. Weaving under non-freeway conditions is classified into two broad categories; basic weave and ramp weave. The analytical models for these two weaving categories are calibrated and validated based on data obtained from several sites selected in the states of New Jersey and New York. New level of service criteria are developed for these two weaving categories. A FORTRAN program was developed to compute average weaving and non-weaving speeds and determine the level of service. In addition, simulation is used to develop a model for basic weave only. The simulation model is microscopic, enabling the user to study the dynamics of individual vehicles and the overall traffic flow.
Direct ramp metering in hierarchical control of freeway systems. Chang, Kai-Kuo, Ph.D. University of Minnesota, 1994. 178 pp. Major Adviser: Yorges J. Stephanedes. Order Number DA9514650 The objective of this research is to develop a direct ramp-metering control method in a hierarchical freeway control system. The function of this direct control is to reduce the effects of traffic disturbances in order to maintain the maximum freeway performance obtained from the upper layer, optimization, in the hierarchical system. The structure of the proposed direct control follows an adaptive optimal control system concept including parameter estimation, state estimation and linear control. In particular, the proposed control employs a Recursive Prediction Error (RPE) method for parameter and state estimation and a linear quadratic regulation (LQR) method for optimal feedback control. To model the behavior of freeway flows, vehicle density of a freeway section is adopted as the state variable in the state equation formulated according to the vehicle conservation principle. Volume and occupancy are measured from detectors as well as proposed parameters. Weighting and conversion factors are formulated into the observation equation. Parameters are designed to handle rapid and random traffic flows, especially for congested flows. Volume and occupancy measurements are arranged to adjust estimates of both the weighting and conversion factors and the vehicle density. These state and observation equations are employed in the RPE method for parameter and state estimation. In addition, a linearized nonlinear traffic flow model based on the vehicle conservation principle is developed for designing a linear quadratic regulator to determine the optimal ramp-metering rates. The proposed direct control method can manage non-congested and congested traffic flows with measurements from current detection systems.
74
Recent doctoral dissertations
Two applications, a hypothetical freeway and a real freeway segment of I-494 in Minneapolis, Minnesota, are illustrated.
Frequency of encounters between vehicles on twc~lane roads and tbeii etkcts on traiIic flow. We&r, Frank, Dr.-Ing. Ruhr-University Bochum (Germany), 1996. 133 pp. (in German).
Dynamics of freeway capacity: Consequences of systematic and environmental influenced fluctuations of speeds and their descriptions in traffic flow models. Ponzlet, Martin, Ph.D. Ruhr- Universify Bochum (Germany), 1996. 234 pp. (in German).
This dissertation develops a theory of encounters between vehicles in opposing traffic flows on single carriageway bi-directional streets. The results are based on theory, empirical research and simulation. The innovative aspect of the approach is that results of video-based microscopic delay studies are introduced into the simulation program. This program isolates the relationship between street width, vehicle size distribution and delays. It is possible to represent these effects on macroscopic ffow characteristics.
Freeway capacity analysis typically regards traffic volume and traffic mix as the fundamental variables influencing capacity. In this dissertation. time is also taken into account. There are two types of time-related influences. The first includes environmental factors like daylight/darkness or weather conditions. The second type is induced by varying driver behavior and traffic mix. Here, seasonal variations over the year and also over the days of the week can be found. The dynamics of freeway capacity are described by three traffic flow models. Traffic flow theory fundamentals like data aggregation, lane usage, breakdown situations and capacity drop are also analyzed.
Enhanced traffic delay models for isolated intersections and congested arterials. Li, Jing, Ph.D. University of Illinois at Chicago, 1994. 182 pp. Order Number DA9516684 Traffic delay models play significant roles in realtime intelligent transportation systems. Different types of roadways and control devices have associated with them different delay functions. In this study, isolated signalized intersections with vehicle-actuated control, and congested signalized arterials with pretimed control, are identified as two important areas requiring improved delay estimation methods. Enhanced delay models that provide a more accurate estimation of signal performance are presented. A macroscopic, stochastic, cycle-by-cycle simulation model was modified by the author to study the capacity and delays for the basic fully-actuated operation. The overflow delay was estimated as the difference between the simulated approach delay and the computed Webster’s uniform delay based on simulated signal timing parameters. Separate models are calibrated for different values of controller unit extensions. The analytical models for estimating average signal timing parameters for basic fullyactuated control operation are also derived. In the case of signalized arterials, signal approaches release traffic at no more than some maximum value corresponding to the signal capacity in congested flow conditions. This is referred to as signal metering effect. This effect reduces demand at the downstream intersection and results in more uniform arrivals from cycle to cycle. Thus, isolated intersection delay formulae based on the assumption of random arrivals may seriously overestimate delays for signalized arterials. In this study, analytical overflow delay models for signalized arterials accounting for signal metering effect are developed. The analytical models are founded on the random queue model.
A fuzzy model of the change and clearance intervals at a signalized intersection. Kou, Kuang Yang, PH.D. The University of Texus at Arlington, 1995. 148 pp. Co-supervisors: H. W. Corley; J. C. Williams. Order Number DA9536120 This dissertation documents the development of a new procedure to calculate the change and clearance intervals of a traffic signal from a rule-based fuzzy logic system. This procedure is based on the theory that driver decision making at signalized intersections is based on imprecise or fuzzy information. The procedure requires no analytical or mathematical modeling of the system’s phenomena and provides the flexibility for modification to improve the performance of the system. The system’s input variables consist of three primary variables and two secondary variables which reflect driver behavior, as well as intersection traffic conditions and geometric layout. Membership function values for the system’s inputs were designed from field studies, simulations, and previous research. The primary variables contribute to the system’s flexibility in that they are easily collected by sensors or detectors. Thus, the procedure provides dynamic change and clearance intervals, which improve the intersection throughput. Several scenarios were tested, and the resulting system indicates a simple but efficient way of determining the change and clearance intervals. The simulated change interval ranges from 3.7s to 4.7s, while the clearance interval is between 0.5s and 1.5s. which compares favorably with traditional methods. The study also shows that more than one variable affects the change and clearance intervals.
Microscopic modelling of freeway operations. Bunker, Jonathan, Ph.D. Queensland University of Technology (Australia), 1996. 456 pp. Supervisor: Rod Troutbeck. Many freeways now experience demand flows in of capacity. Empirical macroscopic excess relationships have been used to relate speed, flow and density to quantify freeway operations and performance. Although these relationships are
An analysis of the effectiveness of high-occupancy vehicle lanes. Dahlgren, Joy Wilbrand, Ph.D. University of California, Berkeley, 1994. 186 pp. Chair: Adib Kanafani. Order Number DA9529279 The success of a high occupancy vehicle (HOV) lane in motivating people to shift to HOVs depends on maintaining a travel time differential between it and the adjacent general purpose lanes. This differential exists only if there is continuing delay on the general purpose lanes. Therefore, it is not clear that construction of an HOV lane will always reduce delay more than construction of a general purpose lane. The objective of this research is to determine the circumstances in which this would be the case. The hypothesis is that such circumstances would be quite limited, and this proves to be the case. The intended benefits of HOV lanes are defined as reduced person-delay and reduced emissions. A model is developed to calculate these benefits for four alternatives: add an HOV lane, add a general purpose lane, convert an existing lane to an HOV lane, and do nothing. Application of the model in typical situations shows that with initial delays on the order of 15 minutes or more, adding an HOV lane would provide substantial reductions in delay and some reduction in emissions. However, in a wide range of such situations, adding a general purpose lane would be even more effective. Only if the initial delay is long and the proportion of HOVs falls in a rather narrow range would an added HOV lane be more effective. The proportion of HOVs must be such that it allows good utilization of the HOV lane while maintaining a sufficient travel time dif? erential to motivate a shift to HOVs. Adding an HOV lane to a three lane freeway will be more effective than adding a general purpose lane only if the initial maximum delay is on the order of 35 minutes or more and the proportion of HOVs is on the order of 20%. Federal policies encourage construction of HOV lanes and do not provide funding for general purpose lanes in areas that have not attained air quality standards. The findings of this research suggest a need to reconsider these policies.
Analytical and simulation models of weaving area operations under non-freeway conditions. Iqbal, Muhammad Shahid. Ph.D. New Jersey Institute of
13
Technology, 1994. 280 pp. Adviser: Athanassios K. Bladikas. Order Numkr DA9514444 This research presents a state-of-the-art analytical approach and simulation models for the analysis of the level of service and operation of non-freeway weaving areas. Weaving under non-freeway conditions is classified into two broad categories; basic weave and ramp weave. The analytical models for these two weaving categories are calibrated and validated based on data obtained from several sites selected in the states of New Jersey and New York. New level of service criteria are developed for these two weaving categories. A FORTRAN program was developed to compute average weaving and non-weaving speeds and determine the level of service. In addition, simulation is used to develop a model for basic weave only. The simulation model is microscopic, enabling the user to study the dynamics of individual vehicles and the overall traffic flow.
Direct ramp metering in hierarchical control of freeway systems. Chang, Kai-Kuo, Ph.D. University of Minnesota, 1994. 178 pp. Major Adviser: Yorges J. Stephanedes. Order Number DA9514650 The objective of this research is to develop a direct ramp-metering control method in a hierarchical freeway control system. The function of this direct control is to reduce the effects of traffic disturbances in order to maintain the maximum freeway performance obtained from the upper layer, optimization, in the hierarchical system. The structure of the proposed direct control follows an adaptive optimal control system concept including parameter estimation, state estimation and linear control. In particular, the proposed control employs a Recursive Prediction Error (RPE) method for parameter and state estimation and a linear quadratic regulation (LQR) method for optimal feedback control. To model the behavior of freeway flows, vehicle density of a freeway section is adopted as the state variable in the state equation formulated according to the vehicle conservation principle. Volume and occupancy are measured from detectors as well as proposed parameters. Weighting and conversion factors are formulated into the observation equation. Parameters are designed to handle rapid and random traffic flows, especially for congested flows. Volume and occupancy measurements are arranged to adjust estimates of both the weighting and conversion factors and the vehicle density. These state and observation equations are employed in the RPE method for parameter and state estimation. In addition, a linearized nonlinear traffic flow model based on the vehicle conservation principle is developed for designing a linear quadratic regulator to determine the optimal ramp-metering rates. The proposed direct control method can manage non-congested and congested traffic flows with measurements from current detection systems.
74
Recent doctoral dissertations
Two applications, a hypothetical freeway and a real freeway segment of I-494 in Minneapolis, Minnesota, are illustrated.
Frequency of encounters between vehicles on twc~lane roads and tbeii etkcts on traiIic flow. We&r, Frank, Dr.-Ing. Ruhr-University Bochum (Germany), 1996. 133 pp. (in German).
Dynamics of freeway capacity: Consequences of systematic and environmental influenced fluctuations of speeds and their descriptions in traffic flow models. Ponzlet, Martin, Ph.D. Ruhr- Universify Bochum (Germany), 1996. 234 pp. (in German).
This dissertation develops a theory of encounters between vehicles in opposing traffic flows on single carriageway bi-directional streets. The results are based on theory, empirical research and simulation. The innovative aspect of the approach is that results of video-based microscopic delay studies are introduced into the simulation program. This program isolates the relationship between street width, vehicle size distribution and delays. It is possible to represent these effects on macroscopic ffow characteristics.
Freeway capacity analysis typically regards traffic volume and traffic mix as the fundamental variables influencing capacity. In this dissertation. time is also taken into account. There are two types of time-related influences. The first includes environmental factors like daylight/darkness or weather conditions. The second type is induced by varying driver behavior and traffic mix. Here, seasonal variations over the year and also over the days of the week can be found. The dynamics of freeway capacity are described by three traffic flow models. Traffic flow theory fundamentals like data aggregation, lane usage, breakdown situations and capacity drop are also analyzed.
Enhanced traffic delay models for isolated intersections and congested arterials. Li, Jing, Ph.D. University of Illinois at Chicago, 1994. 182 pp. Order Number DA9516684 Traffic delay models play significant roles in realtime intelligent transportation systems. Different types of roadways and control devices have associated with them different delay functions. In this study, isolated signalized intersections with vehicle-actuated control, and congested signalized arterials with pretimed control, are identified as two important areas requiring improved delay estimation methods. Enhanced delay models that provide a more accurate estimation of signal performance are presented. A macroscopic, stochastic, cycle-by-cycle simulation model was modified by the author to study the capacity and delays for the basic fully-actuated operation. The overflow delay was estimated as the difference between the simulated approach delay and the computed Webster’s uniform delay based on simulated signal timing parameters. Separate models are calibrated for different values of controller unit extensions. The analytical models for estimating average signal timing parameters for basic fullyactuated control operation are also derived. In the case of signalized arterials, signal approaches release traffic at no more than some maximum value corresponding to the signal capacity in congested flow conditions. This is referred to as signal metering effect. This effect reduces demand at the downstream intersection and results in more uniform arrivals from cycle to cycle. Thus, isolated intersection delay formulae based on the assumption of random arrivals may seriously overestimate delays for signalized arterials. In this study, analytical overflow delay models for signalized arterials accounting for signal metering effect are developed. The analytical models are founded on the random queue model.
A fuzzy model of the change and clearance intervals at a signalized intersection. Kou, Kuang Yang, PH.D. The University of Texus at Arlington, 1995. 148 pp. Co-supervisors: H. W. Corley; J. C. Williams. Order Number DA9536120 This dissertation documents the development of a new procedure to calculate the change and clearance intervals of a traffic signal from a rule-based fuzzy logic system. This procedure is based on the theory that driver decision making at signalized intersections is based on imprecise or fuzzy information. The procedure requires no analytical or mathematical modeling of the system’s phenomena and provides the flexibility for modification to improve the performance of the system. The system’s input variables consist of three primary variables and two secondary variables which reflect driver behavior, as well as intersection traffic conditions and geometric layout. Membership function values for the system’s inputs were designed from field studies, simulations, and previous research. The primary variables contribute to the system’s flexibility in that they are easily collected by sensors or detectors. Thus, the procedure provides dynamic change and clearance intervals, which improve the intersection throughput. Several scenarios were tested, and the resulting system indicates a simple but efficient way of determining the change and clearance intervals. The simulated change interval ranges from 3.7s to 4.7s, while the clearance interval is between 0.5s and 1.5s. which compares favorably with traditional methods. The study also shows that more than one variable affects the change and clearance intervals.
Microscopic modelling of freeway operations. Bunker, Jonathan, Ph.D. Queensland University of Technology (Australia), 1996. 456 pp. Supervisor: Rod Troutbeck. Many freeways now experience demand flows in of capacity. Empirical macroscopic excess relationships have been used to relate speed, flow and density to quantify freeway operations and performance. Although these relationships are