Nagui Rouphail | North Carolina State University (original) (raw)
Papers by Nagui Rouphail
Transportation Research Board 96th Annual MeetingTransportation Research Board, 2017
1 The freeway facilities methodology in the HCM provides a macroscopic simulation environment 2 b... more 1 The freeway facilities methodology in the HCM provides a macroscopic simulation environment 2 based on the Cell Transmission Model (CTM) that can be used to evaluate the performance of a 3 freeway facility. Like all simulation approaches, this methodology must be calibrated for each 4 specific location to ensure valid performance predictions. This presents a major challenge for 5 analysts using the methodology, as the manual provides only limited guidance concerning 6 calibration. 7 The upcoming 6 edition update of the HCM includes a procedural approach to calibrate 8 the analysis which sequentially adjusts traffic demand, free flow speed (FFS), and bottleneck 9 capacities. However, this guidance remains limited and can require a time-consuming manual 10 calibration process. In addition, to match the performance measures of the analysis with real world 11 data, analysts must walk through a challenging series of trial and error steps. 12 This paper presents an automated approach for the HCM bottleneck capacity calibration 13 process that can significantly reduce the time and effort needed for analysis. The approach is rooted 14 in mathematical optimization techniques and uses a genetic algorithm (GA) metaheuristic to 15 estimate capacity adjustment factors that identify facility bottlenecks. The GA optimizes the 16 capacity adjustments such that they result in predicted performance measures consistent with real17 world data. The proposed procedure has been implemented alongside FREEVAL, the official 18 computational engine for the HCM-based freeway analysis. The framework is shown to succeed 19 in improving reported performance measures of the analysis that align with observed real world 20 data. 21 22
Transportation Research Record, 2005
arXiv (Cornell University), Aug 1, 2019
The paper proposes a low-cost system to capture spatial vehicle headway data and process the raw ... more The paper proposes a low-cost system to capture spatial vehicle headway data and process the raw data by filtering outliers using a novel filtering process. Multiple sensors and modules are integrated to form the system. The sensors used are compact, lightweight, low-cost and have low power consumption. A single beam 1-Dimensional Light Detection and Ranging (LIDAR) was used for capturing the space headway data, a Global Positioning System (GPS) to map each data point with a timestamp and position and also a camera to capture video data with an overlay of date, time, distance and speed in real-time. The filtering technique utilizes the Autoregressive Integrated Moving Average (ARIMA) prediction modeling and mean-filtering. The data captured is stored in a Raspberry Pi module. The data is later processed by using the filtering technique to obtain the least outliers. The overall system has enabled to capture spatial headway data and speed of the vehicle at a very low cost and the data obtained can be used for car-following model analysis and speed-density analysis.
Transportation Research Record: Journal of the Transportation Research Board
Signal retiming is a cost-effective practice to improve intersection operations through periodic ... more Signal retiming is a cost-effective practice to improve intersection operations through periodic updating of the timing plans. Traditionally, signal retiming has focused on vehicular-based performance (e.g., reducing vehicle delay or number of stops), while often unintentionally ignoring the needs of other users, such as pedestrians, cyclists, and transit vehicle passengers. This unintended omission is further exacerbated by the signal timing tools used in the industry, which tend to primarily report vehicular metrics. To address these challenges, this research developed a multimodal signal timing framework along with easy-to-use performance measures. These performance measures include (1) vehicle delay, (2) crosswalk delay, (3) crossing stress, and (4) bus delay. To assess the approach effectiveness, the proposed framework and the developed tools were applied to 12 intersections along the North Glebe Corridor, in Arlington, VA, for the weekday a.m. peak. Analysis results showed tha...
University Transportation Centers Program (U.S.), Nov 1, 2019
2019PDFTech ReportLaval, Jorge A.Rouphail, Nagui M.Turochy, Rod EYin, YafengSoutheastern Transpor... more 2019PDFTech ReportLaval, Jorge A.Rouphail, Nagui M.Turochy, Rod EYin, YafengSoutheastern Transportation Research, Innovation, Development and Education Center (STRIDE)University of Florida. Transportation InstituteUnited States. Department of Transportation. University Transportation Centers (UTC) ProgramUniversity Transportation Centers Program (U.S.)United StatesCalibrationConnected vehiclesDynamic traffic assignmentFreeway management systemsHeadwaysHighway capacityOptimizationReliabilityTraffic incidentsTraffic simulationTravel timeValidation69A3551747104Final Report Project IImproving travel time reliability is at the core of battling traffic congestion. This report summarizes the findings from a multi-institutional effort for analyzing and improving freeway travel time reliability. It first investigates the effect of incidents on freeway segment capacity, enabling the calibration and validation of the emergent travel time distribution for a baseline condition of a freeway facility using the Highway Capacity Manual approach. The report then develops a unified framework for assessing the freeway travel time reliability, and then it proposes a new strategy of controlling the headways of cooperative connected vehicles to improve travel time reliability. It also presents a prototype micro-level simulation application, GTsim, which analyzes freeway network performance under various types of Active Traffic Management (ATM) strategies, including those aiming to improve travel time reliability. Lastly, the report reviews the safety benefits of ATM strategies.112
arXiv: Signal Processing, 2019
The paper proposes a low-cost system to capture spatial vehicle headway data and process the raw ... more The paper proposes a low-cost system to capture spatial vehicle headway data and process the raw data by filtering outliers using a novel filtering process. Multiple sensors and modules are integrated to form the system. The sensors used are compact, lightweight, low-cost and have low power consumption. A single beam 1-Dimensional Light Detection and Ranging (LIDAR) was used for capturing the space headway data, a Global Positioning System (GPS) to map each data point with a timestamp and position and also a camera to capture video data with an overlay of date, time, distance and speed in real-time. The filtering technique utilizes the Autoregressive Integrated Moving Average (ARIMA) prediction modeling and mean-filtering. The data captured is stored in a Raspberry Pi module. The data is later processed by using the filtering technique to obtain the least outliers. The overall system has enabled to capture spatial headway data and speed of the vehicle at a very low cost and the data...
Transportation Research Record: Journal of the Transportation Research Board, 2020
This research proposes a new modeling framework for the analysis of freeway segments. The framewo... more This research proposes a new modeling framework for the analysis of freeway segments. The framework provides a continuum from the operation of ramp weave segments to an equivalent basic segment serving the same traffic with the same number of lanes and free-flow speed. This approach distinguishes between congestion effects caused by high v/c ratios from turbulence caused by merging, diverging, and weaving traffic, thus greatly simplifying the model form, and its extensibility to other freeway segment types. The paper presents an application of this new framework to the analysis of ramp weaves, which were not sufficiently sampled in the development of the HCM6 methodology. The proposed model is shown to be superior to the HCM6 method both in relation to explaining field observations of speeds and in its simplicity in application. The results include a new formula for capacity estimation that is highly sensitive to segment length, and a speed estimation model that converges for low we...
Transportation Research Record: Journal of the Transportation Research Board, 2019
Concerns have been raised about the HCM6 weaving method’s lack of sensitivity to weaving segment ... more Concerns have been raised about the HCM6 weaving method’s lack of sensitivity to weaving segment length. This study explores the trends in HCM6 as they relate to lane change estimates and their impact on the segment speed and level of service (LOS). The study also compares HCM6 estimates of lane changes against empirical data from an NGSIM weaving site. Thus, the objectives of this study are twofold: ( a) critically investigate the effect of weaving length on lane change and associated speed model estimates in HCM6, and ( b) analyze trends in lane changes against congestion levels using detailed NGSIM trajectory data, comparing against HCM6 estimates. For ( a) it was found that the lack of sensitivity to weave length is because of the absence of this parameter in the nonweaving lane change and speed models. For ( b), a comparison of HCM6 lane change rates with NGSIM, US-101 data confirmed that the HCM6 estimates for weaving vehicles are fully consistent with those at the NGSIM site,...
Proceedings of VNIS '93 - Vehicle Navigation and Information Systems Conference
The ADVANCE project will be testing the concepts of dynamic route guidance in the Test Area, a 30... more The ADVANCE project will be testing the concepts of dynamic route guidance in the Test Area, a 300 square mile region in north west suburban Chicago. The Traffic Information Center (TIC) will be transmitting to the Mobile Navigation Assistants (MNAs) installed in the test ...
This report describes the process and results of field studies of saturation flow rates for studi... more This report describes the process and results of field studies of saturation flow rates for studies of exclusive left turn lanes conducted in small urban areas in Illinois. Thirteen intersection sites were selected in Rockford, Quad Cities, Springfield, Bloomington and Kankakee. Single left turn lanes were classified into protected-only phasing (3 sites), permissive-only phasing (3) and protected-permissive phasing (4). Dual-left turn lanes in protected-only phasing were investigated at three sites. Parameters were compared with their counterpart values measured in the Chicago Metropolitan area. Data are reported on the basis of the mean and standard deviation of the mean saturation flow rates observed for vehicles in the fourth and subsequent position in the queue. Further, using the ideal saturation flow rate for through traffic in small urban areas of 1800 pcph, the equivalent left turn adjustment factor (f sub LT) was calcualted. Data from the permissive-only sites (3) did not meet the above criterion, as queues on the left turn and opposing approach were very short precluding further analysis. However, the permissive portion of the protected-permissive phase did yield adequate data for analysis. Consistent with previous findings in the literature, saturation flow rates for exclusive left turn lanes in small urban areas were always smaller than those observed in the Chicago area. This was true for every left turn treatment calibrated. It is proposed to use the following saturation flow rates in downstate locations. For permissive-only sites we recommend the use of the Chicago area factors until further data are collected: 1) through-only lanes: 1800 vph/lane; 2) exclusive single LT-protected-only: 1705 vph/lane; 3) dual LT lanes-protected-only: 3424 vph. Recommendations are also given for the calibration of the left turn factor for the permissive portion of protected-permissive LT phases.
Chapter 4 of the 1985 Highway Capacity Manual uses weaving and nonweaving speeds as measures of e... more Chapter 4 of the 1985 Highway Capacity Manual uses weaving and nonweaving speeds as measures of effectiveness (MOEs) to evaluate the quality of service in freeway weaving sections. However, recent research suggests that speed may not be a reliable indicator of traffic performance. Speed and conflict rates (in particular, lane change (LC) and rear-end (RE) conflicts) are tested in terms of their sensitivity to geometric and flow variables. The testing environment is a microscopic simulation model developed for FHWA named Integrated Transportation Simulation (INTRAS), which has been extensively validated on freeway segments throughout the country. For simple one-sided freeway weaving sections, proposed conflict rates were found to be potentially more effective than speeds as an MOE. This finding is demonstrated by a higher sensitivity of the conflict rates MOE compared with the speed MOE to several geometric and flow variables at the weaving section. LC and RE conflict rates were sensitive to changes in the volume-to-capacity ratio (VC), reaching their maximum level for VC in the range 0.9 to 1.0. LC and RE conflict rates were also sensitive to changes in the volume ratio (VR), reaching their maximum level for VR in the range 0.3 to 0.5.
This paper presents a set of analytical models for estimating progression adjustment factors (PAF... more This paper presents a set of analytical models for estimating progression adjustment factors (PAFs) to delays at signalized, coordinated intersection approaches. The derived models are sensitive to the size and flow rate of platoons, which in turn are affected by the travel time between intersections. The procedure requires data that are readily available from time-space diagrams and flow counts. A comparison of the factors estimated in this study and their Highway Capacity Manual (HCM) counterparts reveals the limitations of the HCM method in predicting levels of service for coordinated approaches, especially under excellent or very poor progression scenarios. Finally, an interactive, computerized procedure is presented that carries out the necessary PAF calculations with minimal input requirements.
Urban and Regional Transportation Modeling
3. Combined travel forecasting models: formulations and algorithms 43 Hillel Bar-Gera and David B... more 3. Combined travel forecasting models: formulations and algorithms 43 Hillel Bar-Gera and David Boyce 4. Iteration-free microassignment 58 Michael Wegener 5. Cost minimizing behavior in random discrete choice modeling 70 Sven Erlander and Jan T. Lundgren 6. A modified iterative scheme for the equilibrium traffic signal setting problem 83 Claudio Meneguzzer 7. Transport and location effects of a ring road in a city with or without road pricing 113 Lars-Göran Mattsson and Lina Sjölin 8. Optimal integrated pricing in a bi-modal transportation network 134
Transportation Research Record: Journal of the Transportation Research Board, 1997
Average delay per vehicle is the primary measure for determining the level of service at signaliz... more Average delay per vehicle is the primary measure for determining the level of service at signalized intersections. This performance measure is also a major component in the calculation of average travel speed used to determine the level of service on arterial streets. The most widely used models for estimating delay at signalized intersections are those in Chapters 9 ("Signalized Intersections") and 11 ("Urban and Suburban Arterials") of the Highway Capacity Manual. This research reviewed the literature on models for estimating delay at signalized intersections to identify limitations and formulate revised models to address those limitations. Specific problems that were addressed included the inability to account for actuated-control parameters, oversaturation and variable demand, and metering and filtering by upstream traffic signals. The research team developed a generalized delay model to address these limitations and then validated the generalized model with ...
Transportation Research Record, 2001
Transportation Research Record: Journal of the Transportation Research Board, 2008
Modeling travelers’ perception of service quality is an emerging research area in surface transpo... more Modeling travelers’ perception of service quality is an emerging research area in surface transportation. The first national effort to study automobile drivers’ perceptions is NCHRP Project 3-70. The study was developed in response to agencies’ needs to understand which factors enter into users’ perception of quality of service and the interaction between modes on urban streets. This paper describes the research efforts taken to analyze and model automobile level of service (LOS) from the driver's perspective. A data collection approach using video laboratories and a modeling approach suitable for the discrete and ordered nature of the response variable were selected. The approach enabled the estimation of the distribution of LOS responses, given a set of explanatory variables that describe the geometry and operational effectiveness of the urban street facility. Analysis indicated that participants’ responses tended to be highly variable and that models that characterize the dis...
Transportation Research Record: Journal of the Transportation Research Board, 2004
The pedestrian crossing process in roundabout areas is modeled as a two-stage crossing demarked b... more The pedestrian crossing process in roundabout areas is modeled as a two-stage crossing demarked by a splitter island. A composite queuing system is used to describe the process. The system was simulated by using Arena, a general-purpose simulator chosen for its convenient flowchart modeling capability and vast built-in statistical analysis tools. The model outputs indicate that this composite model is able to provide basic insights into the pedestrian crossing process. Sensitivity analyses revealed that often-overlooked traffic parameters, such as the pedestrian holding space in the splitter island, could have significant impacts on pedestrian crossing performance and capacity.
Transportation Research Board 96th Annual MeetingTransportation Research Board, 2017
1 The freeway facilities methodology in the HCM provides a macroscopic simulation environment 2 b... more 1 The freeway facilities methodology in the HCM provides a macroscopic simulation environment 2 based on the Cell Transmission Model (CTM) that can be used to evaluate the performance of a 3 freeway facility. Like all simulation approaches, this methodology must be calibrated for each 4 specific location to ensure valid performance predictions. This presents a major challenge for 5 analysts using the methodology, as the manual provides only limited guidance concerning 6 calibration. 7 The upcoming 6 edition update of the HCM includes a procedural approach to calibrate 8 the analysis which sequentially adjusts traffic demand, free flow speed (FFS), and bottleneck 9 capacities. However, this guidance remains limited and can require a time-consuming manual 10 calibration process. In addition, to match the performance measures of the analysis with real world 11 data, analysts must walk through a challenging series of trial and error steps. 12 This paper presents an automated approach for the HCM bottleneck capacity calibration 13 process that can significantly reduce the time and effort needed for analysis. The approach is rooted 14 in mathematical optimization techniques and uses a genetic algorithm (GA) metaheuristic to 15 estimate capacity adjustment factors that identify facility bottlenecks. The GA optimizes the 16 capacity adjustments such that they result in predicted performance measures consistent with real17 world data. The proposed procedure has been implemented alongside FREEVAL, the official 18 computational engine for the HCM-based freeway analysis. The framework is shown to succeed 19 in improving reported performance measures of the analysis that align with observed real world 20 data. 21 22
Transportation Research Record, 2005
arXiv (Cornell University), Aug 1, 2019
The paper proposes a low-cost system to capture spatial vehicle headway data and process the raw ... more The paper proposes a low-cost system to capture spatial vehicle headway data and process the raw data by filtering outliers using a novel filtering process. Multiple sensors and modules are integrated to form the system. The sensors used are compact, lightweight, low-cost and have low power consumption. A single beam 1-Dimensional Light Detection and Ranging (LIDAR) was used for capturing the space headway data, a Global Positioning System (GPS) to map each data point with a timestamp and position and also a camera to capture video data with an overlay of date, time, distance and speed in real-time. The filtering technique utilizes the Autoregressive Integrated Moving Average (ARIMA) prediction modeling and mean-filtering. The data captured is stored in a Raspberry Pi module. The data is later processed by using the filtering technique to obtain the least outliers. The overall system has enabled to capture spatial headway data and speed of the vehicle at a very low cost and the data obtained can be used for car-following model analysis and speed-density analysis.
Transportation Research Record: Journal of the Transportation Research Board
Signal retiming is a cost-effective practice to improve intersection operations through periodic ... more Signal retiming is a cost-effective practice to improve intersection operations through periodic updating of the timing plans. Traditionally, signal retiming has focused on vehicular-based performance (e.g., reducing vehicle delay or number of stops), while often unintentionally ignoring the needs of other users, such as pedestrians, cyclists, and transit vehicle passengers. This unintended omission is further exacerbated by the signal timing tools used in the industry, which tend to primarily report vehicular metrics. To address these challenges, this research developed a multimodal signal timing framework along with easy-to-use performance measures. These performance measures include (1) vehicle delay, (2) crosswalk delay, (3) crossing stress, and (4) bus delay. To assess the approach effectiveness, the proposed framework and the developed tools were applied to 12 intersections along the North Glebe Corridor, in Arlington, VA, for the weekday a.m. peak. Analysis results showed tha...
University Transportation Centers Program (U.S.), Nov 1, 2019
2019PDFTech ReportLaval, Jorge A.Rouphail, Nagui M.Turochy, Rod EYin, YafengSoutheastern Transpor... more 2019PDFTech ReportLaval, Jorge A.Rouphail, Nagui M.Turochy, Rod EYin, YafengSoutheastern Transportation Research, Innovation, Development and Education Center (STRIDE)University of Florida. Transportation InstituteUnited States. Department of Transportation. University Transportation Centers (UTC) ProgramUniversity Transportation Centers Program (U.S.)United StatesCalibrationConnected vehiclesDynamic traffic assignmentFreeway management systemsHeadwaysHighway capacityOptimizationReliabilityTraffic incidentsTraffic simulationTravel timeValidation69A3551747104Final Report Project IImproving travel time reliability is at the core of battling traffic congestion. This report summarizes the findings from a multi-institutional effort for analyzing and improving freeway travel time reliability. It first investigates the effect of incidents on freeway segment capacity, enabling the calibration and validation of the emergent travel time distribution for a baseline condition of a freeway facility using the Highway Capacity Manual approach. The report then develops a unified framework for assessing the freeway travel time reliability, and then it proposes a new strategy of controlling the headways of cooperative connected vehicles to improve travel time reliability. It also presents a prototype micro-level simulation application, GTsim, which analyzes freeway network performance under various types of Active Traffic Management (ATM) strategies, including those aiming to improve travel time reliability. Lastly, the report reviews the safety benefits of ATM strategies.112
arXiv: Signal Processing, 2019
The paper proposes a low-cost system to capture spatial vehicle headway data and process the raw ... more The paper proposes a low-cost system to capture spatial vehicle headway data and process the raw data by filtering outliers using a novel filtering process. Multiple sensors and modules are integrated to form the system. The sensors used are compact, lightweight, low-cost and have low power consumption. A single beam 1-Dimensional Light Detection and Ranging (LIDAR) was used for capturing the space headway data, a Global Positioning System (GPS) to map each data point with a timestamp and position and also a camera to capture video data with an overlay of date, time, distance and speed in real-time. The filtering technique utilizes the Autoregressive Integrated Moving Average (ARIMA) prediction modeling and mean-filtering. The data captured is stored in a Raspberry Pi module. The data is later processed by using the filtering technique to obtain the least outliers. The overall system has enabled to capture spatial headway data and speed of the vehicle at a very low cost and the data...
Transportation Research Record: Journal of the Transportation Research Board, 2020
This research proposes a new modeling framework for the analysis of freeway segments. The framewo... more This research proposes a new modeling framework for the analysis of freeway segments. The framework provides a continuum from the operation of ramp weave segments to an equivalent basic segment serving the same traffic with the same number of lanes and free-flow speed. This approach distinguishes between congestion effects caused by high v/c ratios from turbulence caused by merging, diverging, and weaving traffic, thus greatly simplifying the model form, and its extensibility to other freeway segment types. The paper presents an application of this new framework to the analysis of ramp weaves, which were not sufficiently sampled in the development of the HCM6 methodology. The proposed model is shown to be superior to the HCM6 method both in relation to explaining field observations of speeds and in its simplicity in application. The results include a new formula for capacity estimation that is highly sensitive to segment length, and a speed estimation model that converges for low we...
Transportation Research Record: Journal of the Transportation Research Board, 2019
Concerns have been raised about the HCM6 weaving method’s lack of sensitivity to weaving segment ... more Concerns have been raised about the HCM6 weaving method’s lack of sensitivity to weaving segment length. This study explores the trends in HCM6 as they relate to lane change estimates and their impact on the segment speed and level of service (LOS). The study also compares HCM6 estimates of lane changes against empirical data from an NGSIM weaving site. Thus, the objectives of this study are twofold: ( a) critically investigate the effect of weaving length on lane change and associated speed model estimates in HCM6, and ( b) analyze trends in lane changes against congestion levels using detailed NGSIM trajectory data, comparing against HCM6 estimates. For ( a) it was found that the lack of sensitivity to weave length is because of the absence of this parameter in the nonweaving lane change and speed models. For ( b), a comparison of HCM6 lane change rates with NGSIM, US-101 data confirmed that the HCM6 estimates for weaving vehicles are fully consistent with those at the NGSIM site,...
Proceedings of VNIS '93 - Vehicle Navigation and Information Systems Conference
The ADVANCE project will be testing the concepts of dynamic route guidance in the Test Area, a 30... more The ADVANCE project will be testing the concepts of dynamic route guidance in the Test Area, a 300 square mile region in north west suburban Chicago. The Traffic Information Center (TIC) will be transmitting to the Mobile Navigation Assistants (MNAs) installed in the test ...
This report describes the process and results of field studies of saturation flow rates for studi... more This report describes the process and results of field studies of saturation flow rates for studies of exclusive left turn lanes conducted in small urban areas in Illinois. Thirteen intersection sites were selected in Rockford, Quad Cities, Springfield, Bloomington and Kankakee. Single left turn lanes were classified into protected-only phasing (3 sites), permissive-only phasing (3) and protected-permissive phasing (4). Dual-left turn lanes in protected-only phasing were investigated at three sites. Parameters were compared with their counterpart values measured in the Chicago Metropolitan area. Data are reported on the basis of the mean and standard deviation of the mean saturation flow rates observed for vehicles in the fourth and subsequent position in the queue. Further, using the ideal saturation flow rate for through traffic in small urban areas of 1800 pcph, the equivalent left turn adjustment factor (f sub LT) was calcualted. Data from the permissive-only sites (3) did not meet the above criterion, as queues on the left turn and opposing approach were very short precluding further analysis. However, the permissive portion of the protected-permissive phase did yield adequate data for analysis. Consistent with previous findings in the literature, saturation flow rates for exclusive left turn lanes in small urban areas were always smaller than those observed in the Chicago area. This was true for every left turn treatment calibrated. It is proposed to use the following saturation flow rates in downstate locations. For permissive-only sites we recommend the use of the Chicago area factors until further data are collected: 1) through-only lanes: 1800 vph/lane; 2) exclusive single LT-protected-only: 1705 vph/lane; 3) dual LT lanes-protected-only: 3424 vph. Recommendations are also given for the calibration of the left turn factor for the permissive portion of protected-permissive LT phases.
Chapter 4 of the 1985 Highway Capacity Manual uses weaving and nonweaving speeds as measures of e... more Chapter 4 of the 1985 Highway Capacity Manual uses weaving and nonweaving speeds as measures of effectiveness (MOEs) to evaluate the quality of service in freeway weaving sections. However, recent research suggests that speed may not be a reliable indicator of traffic performance. Speed and conflict rates (in particular, lane change (LC) and rear-end (RE) conflicts) are tested in terms of their sensitivity to geometric and flow variables. The testing environment is a microscopic simulation model developed for FHWA named Integrated Transportation Simulation (INTRAS), which has been extensively validated on freeway segments throughout the country. For simple one-sided freeway weaving sections, proposed conflict rates were found to be potentially more effective than speeds as an MOE. This finding is demonstrated by a higher sensitivity of the conflict rates MOE compared with the speed MOE to several geometric and flow variables at the weaving section. LC and RE conflict rates were sensitive to changes in the volume-to-capacity ratio (VC), reaching their maximum level for VC in the range 0.9 to 1.0. LC and RE conflict rates were also sensitive to changes in the volume ratio (VR), reaching their maximum level for VR in the range 0.3 to 0.5.
This paper presents a set of analytical models for estimating progression adjustment factors (PAF... more This paper presents a set of analytical models for estimating progression adjustment factors (PAFs) to delays at signalized, coordinated intersection approaches. The derived models are sensitive to the size and flow rate of platoons, which in turn are affected by the travel time between intersections. The procedure requires data that are readily available from time-space diagrams and flow counts. A comparison of the factors estimated in this study and their Highway Capacity Manual (HCM) counterparts reveals the limitations of the HCM method in predicting levels of service for coordinated approaches, especially under excellent or very poor progression scenarios. Finally, an interactive, computerized procedure is presented that carries out the necessary PAF calculations with minimal input requirements.
Urban and Regional Transportation Modeling
3. Combined travel forecasting models: formulations and algorithms 43 Hillel Bar-Gera and David B... more 3. Combined travel forecasting models: formulations and algorithms 43 Hillel Bar-Gera and David Boyce 4. Iteration-free microassignment 58 Michael Wegener 5. Cost minimizing behavior in random discrete choice modeling 70 Sven Erlander and Jan T. Lundgren 6. A modified iterative scheme for the equilibrium traffic signal setting problem 83 Claudio Meneguzzer 7. Transport and location effects of a ring road in a city with or without road pricing 113 Lars-Göran Mattsson and Lina Sjölin 8. Optimal integrated pricing in a bi-modal transportation network 134
Transportation Research Record: Journal of the Transportation Research Board, 1997
Average delay per vehicle is the primary measure for determining the level of service at signaliz... more Average delay per vehicle is the primary measure for determining the level of service at signalized intersections. This performance measure is also a major component in the calculation of average travel speed used to determine the level of service on arterial streets. The most widely used models for estimating delay at signalized intersections are those in Chapters 9 ("Signalized Intersections") and 11 ("Urban and Suburban Arterials") of the Highway Capacity Manual. This research reviewed the literature on models for estimating delay at signalized intersections to identify limitations and formulate revised models to address those limitations. Specific problems that were addressed included the inability to account for actuated-control parameters, oversaturation and variable demand, and metering and filtering by upstream traffic signals. The research team developed a generalized delay model to address these limitations and then validated the generalized model with ...
Transportation Research Record, 2001
Transportation Research Record: Journal of the Transportation Research Board, 2008
Modeling travelers’ perception of service quality is an emerging research area in surface transpo... more Modeling travelers’ perception of service quality is an emerging research area in surface transportation. The first national effort to study automobile drivers’ perceptions is NCHRP Project 3-70. The study was developed in response to agencies’ needs to understand which factors enter into users’ perception of quality of service and the interaction between modes on urban streets. This paper describes the research efforts taken to analyze and model automobile level of service (LOS) from the driver's perspective. A data collection approach using video laboratories and a modeling approach suitable for the discrete and ordered nature of the response variable were selected. The approach enabled the estimation of the distribution of LOS responses, given a set of explanatory variables that describe the geometry and operational effectiveness of the urban street facility. Analysis indicated that participants’ responses tended to be highly variable and that models that characterize the dis...
Transportation Research Record: Journal of the Transportation Research Board, 2004
The pedestrian crossing process in roundabout areas is modeled as a two-stage crossing demarked b... more The pedestrian crossing process in roundabout areas is modeled as a two-stage crossing demarked by a splitter island. A composite queuing system is used to describe the process. The system was simulated by using Arena, a general-purpose simulator chosen for its convenient flowchart modeling capability and vast built-in statistical analysis tools. The model outputs indicate that this composite model is able to provide basic insights into the pedestrian crossing process. Sensitivity analyses revealed that often-overlooked traffic parameters, such as the pedestrian holding space in the splitter island, could have significant impacts on pedestrian crossing performance and capacity.