Transportation Research Record: Journal of the Transportation Research Board
Because of a growing crash occurrence in conflict areas, the ramp and merge segments on freeways ... more Because of a growing crash occurrence in conflict areas, the ramp and merge segments on freeways are a concern for transportation researchers and practitioners. Therefore, short-term safety-performance functions (SPFs) have been proposed to predict crash frequency at a.m. and p.m. peak-period aggregation levels using microscopic traffic-detector data. The proposed short-term crash prediction models could achieve more accuracy and flexibility, give a better understanding of how safety evaluations change over time, and enable the taking of appropriate actions. This study contributes to the literature by using the multivariate Poisson-lognormal (MVPLN) method via an integrated nested Laplace approximation (INLA) approach to investigate the dependency and the correlation between two responses (on-ramp- and merge-related crash frequencies). Models are developed for total crashes (KABCO) and fatal and severe injury crashes (KAB), utilizing 70% of a total 239 and 238 for joint on-ramp and ...
In the cost–benefit analysis of urban transportation investment, a logsum-based benefit calculati... more In the cost–benefit analysis of urban transportation investment, a logsum-based benefit calculation is widely used. However, it is rarely applied to inter-regional transportation. In this study, we applied a logsum-based approach to the calculation of benefits for high-speed projects for inter-regional railways in Korea’s long-term transportation plan. Moreover, we applied a behavioral model in which an agent travels beyond the zones assumed by an aggregate model. In the case of South Korea, such a model is important for determining transportation priorities: whether to specialize in mobility improvement by investing in a high-speed railway project, such as the 300 km/h Korea Train eXpress (KTX), or to improve existing facilities, such as by building a relatively slower railroad (150–250 km/h) to enhance existing mobility and accessibility. In this context, if a new, relatively slow railroad were constructed adjacent to a high-speed railroad, the benefits would be negligible since t...
The Journal of The Korea Institute of Intelligent Transport Systems, 2011
This study presented an algorithm to detect zigzag driving maneuver that is highly associated wit... more This study presented an algorithm to detect zigzag driving maneuver that is highly associated with vehicle crash occurrence. In general, the zigzag driving results from the driver's inattention including drowsy driving and driving while intoxicated. Therefore, the technology to detect such unsafe driving maneuver will provide us with a valuable opportunity to prevent crash in the road. The proposed detection algorithm used angular velocity data obtained from a gyro sensor. Performance evaluations of the algorithm presented promising results for the actual implementation in practice. The outcome of this study can be used as novel information contents under the ubiquitous transportation systems environment.
The Journal of The Korea Institute of Intelligent Transport Systems, 2009
유비쿼터스 환경을 기반으로 하여 돌발상황 발생 시 신뢰성 있는 통행시간 예측을 위해 새로운 개념의 노드-링크 설정 기법을 활용한 대표통행시간 산출기법을 연구하였다. 본 연구에... more 유비쿼터스 환경을 기반으로 하여 돌발상황 발생 시 신뢰성 있는 통행시간 예측을 위해 새로운 개념의 노드-링크 설정 기법을 활용한 대표통행시간 산출기법을 연구하였다. 본 연구에서 제시한 방법론은 교통류의 특성에 따라 링크를 구분하여 개별적인 통행시간을 산출하는 기법이며, 개별차량의 특성을 반영하기 위해 일정 속도단위로 차량분류군을 구분하여 통행시간을 산출하는 방법을 제시하였다. 사고영향권과 사고영향권 상류부, 사고영향권 하류부를 독립적인 링크로 설정 하였으며, 돌발상황 발생 시 나타나는 차로별 통행시간의 특성을 반영하기 위해 통행시간 제공 방법을 차로별로 독립적인 통행시간 제공으로 설정하고, 차로별 통행시간을 산출하였다. 제안된 방법론의 정확도를 MAPE (Mean Absolute Percentage Error)를 이용하여 평가하였고, 프로브차량비율(Percentage of Probe Vehicles: PPV)에 따른 정확도의 변화를 분석하였다. 분석 결과 PPV가 20%이상 확보될 경우 오차율 10% 미만의 정확도를 가지는 것으로 분석되었다. 본 연구는 도래하는 유비쿼터스 교통환경에서 보다 신뢰성 있고, 실시간성 있는 교통정보 생성에 도움이 될 것으로 판단된다. 【This study proposes a methodology for estimating representative section travel times using individual vehicle travel information under the ubiquitous transportation environment (UTE). A novel approach is to substantialize a concept of dynamic node-links in processing trajectory data. Also, grouping vehicles was conducted to obtain more reliable travel times representing characteristics of i...
Transportation Research Record: Journal of the Transportation Research Board, 2015
Accurate and timely predictions of traffic conditions are required for congestion avoidance and r... more Accurate and timely predictions of traffic conditions are required for congestion avoidance and route guidance in real-time freeway traffic operations. Special attention to winter operations is needed because prediction error could be amplified under severe weather conditions involving snow. This study employed a vehicle detection system to propose a speed prediction methodology that used the k–nearest neighbors algorithm. The speed prediction was further evaluated under different weather conditions with a road weather information system. Cross-comparisons of the mean absolute percentage error (MAPE) between three weather conditions (normal, light snow, and heavy snow) revealed that the MAPE tended to increase with increases in the forecasting time step (T) and snow intensity. The marginal MAPE over the time step was larger during heavy snow conditions than under normal and light snow conditions. These findings indicate that for winter freeway operations, the time step should be sel...
Transportation Research Record: Journal of the Transportation Research Board, 2011
The recent advancement of vehicle positioning and wireless communication technologies facilitates... more The recent advancement of vehicle positioning and wireless communication technologies facilitates the development of more sophisticated traffic control and information strategies. This study proposes a methodology for estimating lane-level travel times (L2TT) under an environment referred to as V2X, which includes vehicle-to-vehicle and vehicle-to-infrastructure communications. A framework is presented for a V2X-based traffic information system that is capable of transmitting vehicle positions and speeds, which are used as inputs of the proposed methodology. A concept of establishing temporal nodes and links based on the dynamic change in traffic conditions is proposed to estimate more reliable and accurate L2TT. VISSIM, a microscopic traffic simulator for multimodal traffic flow modeling, is used to evaluate the proposed travel time estimation method. Statistical analysis techniques including analysis of variance and a homogeneity test between data groups are adopted to derive more...
Transportation Research Record: Journal of the Transportation Research Board, 2012
Driver inattentiveness and distraction resulting in unsafe vehicle maneuvers are a significant sa... more Driver inattentiveness and distraction resulting in unsafe vehicle maneuvers are a significant safety concern because such behavior can directly lead to crashes. An effective technical countermeasure is to detect unsafe driving events and provide drivers with advanced warning information. This study presents an intervehicle safety warning information system. An inertial measurement unit consisting of an accelerometer and gyro sensor in addition to a Global Positioning System receiver was used to collect data for the developed algorithm. Vehicle position, speed, acceleration, and angular velocity data were analyzed and were used as inputs for the algorithm. A support vector machine classifier was also incorporated into the algorithm to identify further the severity of unsafe driving events. The performance evaluation results showed that the detection algorithm could capture longitudinal and transverse unsafe driving events. In addition, a prototype of the proposed warning information...
Abstract: Effective detection and correction of outliers in raw traffic data collected from the f... more Abstract: Effective detection and correction of outliers in raw traffic data collected from the field is of keen interest because reliable traffic information is highly dependent on the quality of raw data. Global Positioning System (GPS) based traffic surveillance systems are capable of producing individual vehicle speeds that are invaluable for various traffic management and information strategies. This study proposes a locally weighted regression (LWR) based filtering method for individual vehicle speed data. Both a technique to generate synthetic ...
Effective detection and correction of outliers in raw traffic data collected from the field is of... more Effective detection and correction of outliers in raw traffic data collected from the field is of keen 2 ... The advancement of sensor and communication technologies is increasing the availability of more 2 ... Traffic surveillance systems have advanced from the stage of obtaining aggregated measurements 9 ... This study proposes a methodology based on locally weighted regression (LWR) for detecting and 19 ... The proposed method is expected to be an effective tool for a variety of traffic data processing and 23 ... This paper consists of five sections. Section 2 ...
Transportation Research Record: Journal of the Transportation Research Board
Because of a growing crash occurrence in conflict areas, the ramp and merge segments on freeways ... more Because of a growing crash occurrence in conflict areas, the ramp and merge segments on freeways are a concern for transportation researchers and practitioners. Therefore, short-term safety-performance functions (SPFs) have been proposed to predict crash frequency at a.m. and p.m. peak-period aggregation levels using microscopic traffic-detector data. The proposed short-term crash prediction models could achieve more accuracy and flexibility, give a better understanding of how safety evaluations change over time, and enable the taking of appropriate actions. This study contributes to the literature by using the multivariate Poisson-lognormal (MVPLN) method via an integrated nested Laplace approximation (INLA) approach to investigate the dependency and the correlation between two responses (on-ramp- and merge-related crash frequencies). Models are developed for total crashes (KABCO) and fatal and severe injury crashes (KAB), utilizing 70% of a total 239 and 238 for joint on-ramp and ...
In the cost–benefit analysis of urban transportation investment, a logsum-based benefit calculati... more In the cost–benefit analysis of urban transportation investment, a logsum-based benefit calculation is widely used. However, it is rarely applied to inter-regional transportation. In this study, we applied a logsum-based approach to the calculation of benefits for high-speed projects for inter-regional railways in Korea’s long-term transportation plan. Moreover, we applied a behavioral model in which an agent travels beyond the zones assumed by an aggregate model. In the case of South Korea, such a model is important for determining transportation priorities: whether to specialize in mobility improvement by investing in a high-speed railway project, such as the 300 km/h Korea Train eXpress (KTX), or to improve existing facilities, such as by building a relatively slower railroad (150–250 km/h) to enhance existing mobility and accessibility. In this context, if a new, relatively slow railroad were constructed adjacent to a high-speed railroad, the benefits would be negligible since t...
The Journal of The Korea Institute of Intelligent Transport Systems, 2011
This study presented an algorithm to detect zigzag driving maneuver that is highly associated wit... more This study presented an algorithm to detect zigzag driving maneuver that is highly associated with vehicle crash occurrence. In general, the zigzag driving results from the driver's inattention including drowsy driving and driving while intoxicated. Therefore, the technology to detect such unsafe driving maneuver will provide us with a valuable opportunity to prevent crash in the road. The proposed detection algorithm used angular velocity data obtained from a gyro sensor. Performance evaluations of the algorithm presented promising results for the actual implementation in practice. The outcome of this study can be used as novel information contents under the ubiquitous transportation systems environment.
The Journal of The Korea Institute of Intelligent Transport Systems, 2009
유비쿼터스 환경을 기반으로 하여 돌발상황 발생 시 신뢰성 있는 통행시간 예측을 위해 새로운 개념의 노드-링크 설정 기법을 활용한 대표통행시간 산출기법을 연구하였다. 본 연구에... more 유비쿼터스 환경을 기반으로 하여 돌발상황 발생 시 신뢰성 있는 통행시간 예측을 위해 새로운 개념의 노드-링크 설정 기법을 활용한 대표통행시간 산출기법을 연구하였다. 본 연구에서 제시한 방법론은 교통류의 특성에 따라 링크를 구분하여 개별적인 통행시간을 산출하는 기법이며, 개별차량의 특성을 반영하기 위해 일정 속도단위로 차량분류군을 구분하여 통행시간을 산출하는 방법을 제시하였다. 사고영향권과 사고영향권 상류부, 사고영향권 하류부를 독립적인 링크로 설정 하였으며, 돌발상황 발생 시 나타나는 차로별 통행시간의 특성을 반영하기 위해 통행시간 제공 방법을 차로별로 독립적인 통행시간 제공으로 설정하고, 차로별 통행시간을 산출하였다. 제안된 방법론의 정확도를 MAPE (Mean Absolute Percentage Error)를 이용하여 평가하였고, 프로브차량비율(Percentage of Probe Vehicles: PPV)에 따른 정확도의 변화를 분석하였다. 분석 결과 PPV가 20%이상 확보될 경우 오차율 10% 미만의 정확도를 가지는 것으로 분석되었다. 본 연구는 도래하는 유비쿼터스 교통환경에서 보다 신뢰성 있고, 실시간성 있는 교통정보 생성에 도움이 될 것으로 판단된다. 【This study proposes a methodology for estimating representative section travel times using individual vehicle travel information under the ubiquitous transportation environment (UTE). A novel approach is to substantialize a concept of dynamic node-links in processing trajectory data. Also, grouping vehicles was conducted to obtain more reliable travel times representing characteristics of i...
Transportation Research Record: Journal of the Transportation Research Board, 2015
Accurate and timely predictions of traffic conditions are required for congestion avoidance and r... more Accurate and timely predictions of traffic conditions are required for congestion avoidance and route guidance in real-time freeway traffic operations. Special attention to winter operations is needed because prediction error could be amplified under severe weather conditions involving snow. This study employed a vehicle detection system to propose a speed prediction methodology that used the k–nearest neighbors algorithm. The speed prediction was further evaluated under different weather conditions with a road weather information system. Cross-comparisons of the mean absolute percentage error (MAPE) between three weather conditions (normal, light snow, and heavy snow) revealed that the MAPE tended to increase with increases in the forecasting time step (T) and snow intensity. The marginal MAPE over the time step was larger during heavy snow conditions than under normal and light snow conditions. These findings indicate that for winter freeway operations, the time step should be sel...
Transportation Research Record: Journal of the Transportation Research Board, 2011
The recent advancement of vehicle positioning and wireless communication technologies facilitates... more The recent advancement of vehicle positioning and wireless communication technologies facilitates the development of more sophisticated traffic control and information strategies. This study proposes a methodology for estimating lane-level travel times (L2TT) under an environment referred to as V2X, which includes vehicle-to-vehicle and vehicle-to-infrastructure communications. A framework is presented for a V2X-based traffic information system that is capable of transmitting vehicle positions and speeds, which are used as inputs of the proposed methodology. A concept of establishing temporal nodes and links based on the dynamic change in traffic conditions is proposed to estimate more reliable and accurate L2TT. VISSIM, a microscopic traffic simulator for multimodal traffic flow modeling, is used to evaluate the proposed travel time estimation method. Statistical analysis techniques including analysis of variance and a homogeneity test between data groups are adopted to derive more...
Transportation Research Record: Journal of the Transportation Research Board, 2012
Driver inattentiveness and distraction resulting in unsafe vehicle maneuvers are a significant sa... more Driver inattentiveness and distraction resulting in unsafe vehicle maneuvers are a significant safety concern because such behavior can directly lead to crashes. An effective technical countermeasure is to detect unsafe driving events and provide drivers with advanced warning information. This study presents an intervehicle safety warning information system. An inertial measurement unit consisting of an accelerometer and gyro sensor in addition to a Global Positioning System receiver was used to collect data for the developed algorithm. Vehicle position, speed, acceleration, and angular velocity data were analyzed and were used as inputs for the algorithm. A support vector machine classifier was also incorporated into the algorithm to identify further the severity of unsafe driving events. The performance evaluation results showed that the detection algorithm could capture longitudinal and transverse unsafe driving events. In addition, a prototype of the proposed warning information...
Abstract: Effective detection and correction of outliers in raw traffic data collected from the f... more Abstract: Effective detection and correction of outliers in raw traffic data collected from the field is of keen interest because reliable traffic information is highly dependent on the quality of raw data. Global Positioning System (GPS) based traffic surveillance systems are capable of producing individual vehicle speeds that are invaluable for various traffic management and information strategies. This study proposes a locally weighted regression (LWR) based filtering method for individual vehicle speed data. Both a technique to generate synthetic ...
Effective detection and correction of outliers in raw traffic data collected from the field is of... more Effective detection and correction of outliers in raw traffic data collected from the field is of keen 2 ... The advancement of sensor and communication technologies is increasing the availability of more 2 ... Traffic surveillance systems have advanced from the stage of obtaining aggregated measurements 9 ... This study proposes a methodology based on locally weighted regression (LWR) for detecting and 19 ... The proposed method is expected to be an effective tool for a variety of traffic data processing and 23 ... This paper consists of five sections. Section 2 ...
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