Journal of Intelligent Transportation Systems, 2016
Short-term traffic flow forecasting is a critical function in advanced traffic management systems... more Short-term traffic flow forecasting is a critical function in advanced traffic management systems (ATMS) and advanced traveler information systems (ATIS). Accurate forecasting results are useful to indicate future traffic conditions and assist traffic managers in seeking solutions to congestion problems on urban freeways and surface streets. There is new research interest in short-term traffic flow forecasting due to recent developments in intelligent transportation systems (ITS) technologies. Previous research involves technologies in multiple areas, and a significant number of forecasting methods exist in the literature. However, most studies used univariate forecasting methods, and they have limited forecasting abilities when part of the data is missing or erroneous. While the historical average (HA) method is often applied to deal with this issue, the forecasting accuracy cannot be guaranteed. This article makes use of the spatial relationship of traffic flow at nearby locations and builds up two multivariate forecasting approaches: the vector autoregression (VAR) and the general regression neural network (GRNN) based forecasting models. Traffic data collected from U.S. Highway 290 in Houston, TX, were used to test the model performance. Comparison of performances of the three models (HA, VAR, and GRNN) in different missing ratios and forecasting time intervals indicates that the accuracy of the VAR model is more sensitive to the missing ratio, while on average the GRNN model gives more robust and accurate forecasting with missing data, particularly when the missing data ratio is high.
This paper presents an overview of the concept and features of the CORSIM traffic simulation prog... more This paper presents an overview of the concept and features of the CORSIM traffic simulation program and the TSIS package that provides an integrated, user-friendly interface and environment for executing CORSIM. The new functions and feature of CORSIM and TSIS in the most recent release are highlighted. Several successful TSIS/CORSIM applications are used to demonstrate that CORSIM is a very effective tool to perform traffic operations analysis and to evaluate new ITS technologies.
Transportation Research Record: Journal of the Transportation Research Board, 2003
In CORSIM (CORridor SIMulation) 4.32, a simplified gravity model was implemented in the freeway n... more In CORSIM (CORridor SIMulation) 4.32, a simplified gravity model was implemented in the freeway network to convert user input turning percentages to origin-destination (O-D) trip percentages. During the conversion, there were no O-D volume calculations or iterations to balance the destination volumes. The unbalanced destination volumes were directly converted to the turning percentages, which were different from the ones the user specified. These deficiencies in CORSIM 4.32 were corrected in the 5.0 and later versions with the procedures and methodologies described. First a linear system is introduced to obtain the O-D volumes from the entrance volumes and the ramp turning percentages, which are specified by the CORSIM user. The gravity model in CORSIM is different from the traditional gravity model in that a CORSIM user can specify certain O-D trips (in percentages) as constraints. Therefore, the O-D trip table is split into a user-specified O-D trip table and a table for the gravi...
Transportation Research Record: Journal of the Transportation Research Board, 2011
This research aimed to develop a methodology for analyzing the platoon impacts on major-street le... more This research aimed to develop a methodology for analyzing the platoon impacts on major-street left-turn (MSLT) delay at two-way stop-controlled intersections. The main idea was to use a microscopic simulation tool to simulate different platoon scenarios in opposing through traffic and then to apply regression models to capture the impacts of platoons on the delay of MSLT. Two platoon variables were adopted as a simplification of the complex platoon scenarios to make analysis of the platoon effects on MSLT delay practical. The first two steps were to build simulation models for real-world unsignalized intersections and simulate scenarios with a combination of various factors related to platoons in VISSIM simulation. The models were calibrated with field data before simulation started. The next step was to define, derive, and calibrate two platoon variables for describing the duration and intensity of platoon arrivals in the opposing through traffic. This process effectively simplifi...
This paper presents an overview of the concept and features of the CORSIM traffic simulation prog... more This paper presents an overview of the concept and features of the CORSIM traffic simulation program and the TSIS package that provides an integrated, user-friendly interface and environment for executing CORSIM. The new functions and feature of CORSIM and TSIS in the most ...
Journal of Intelligent Transportation Systems, 2016
Short-term traffic flow forecasting is a critical function in advanced traffic management systems... more Short-term traffic flow forecasting is a critical function in advanced traffic management systems (ATMS) and advanced traveler information systems (ATIS). Accurate forecasting results are useful to indicate future traffic conditions and assist traffic managers in seeking solutions to congestion problems on urban freeways and surface streets. There is new research interest in short-term traffic flow forecasting due to recent developments in intelligent transportation systems (ITS) technologies. Previous research involves technologies in multiple areas, and a significant number of forecasting methods exist in the literature. However, most studies used univariate forecasting methods, and they have limited forecasting abilities when part of the data is missing or erroneous. While the historical average (HA) method is often applied to deal with this issue, the forecasting accuracy cannot be guaranteed. This article makes use of the spatial relationship of traffic flow at nearby locations and builds up two multivariate forecasting approaches: the vector autoregression (VAR) and the general regression neural network (GRNN) based forecasting models. Traffic data collected from U.S. Highway 290 in Houston, TX, were used to test the model performance. Comparison of performances of the three models (HA, VAR, and GRNN) in different missing ratios and forecasting time intervals indicates that the accuracy of the VAR model is more sensitive to the missing ratio, while on average the GRNN model gives more robust and accurate forecasting with missing data, particularly when the missing data ratio is high.
This paper presents an overview of the concept and features of the CORSIM traffic simulation prog... more This paper presents an overview of the concept and features of the CORSIM traffic simulation program and the TSIS package that provides an integrated, user-friendly interface and environment for executing CORSIM. The new functions and feature of CORSIM and TSIS in the most recent release are highlighted. Several successful TSIS/CORSIM applications are used to demonstrate that CORSIM is a very effective tool to perform traffic operations analysis and to evaluate new ITS technologies.
Transportation Research Record: Journal of the Transportation Research Board, 2003
In CORSIM (CORridor SIMulation) 4.32, a simplified gravity model was implemented in the freeway n... more In CORSIM (CORridor SIMulation) 4.32, a simplified gravity model was implemented in the freeway network to convert user input turning percentages to origin-destination (O-D) trip percentages. During the conversion, there were no O-D volume calculations or iterations to balance the destination volumes. The unbalanced destination volumes were directly converted to the turning percentages, which were different from the ones the user specified. These deficiencies in CORSIM 4.32 were corrected in the 5.0 and later versions with the procedures and methodologies described. First a linear system is introduced to obtain the O-D volumes from the entrance volumes and the ramp turning percentages, which are specified by the CORSIM user. The gravity model in CORSIM is different from the traditional gravity model in that a CORSIM user can specify certain O-D trips (in percentages) as constraints. Therefore, the O-D trip table is split into a user-specified O-D trip table and a table for the gravi...
Transportation Research Record: Journal of the Transportation Research Board, 2011
This research aimed to develop a methodology for analyzing the platoon impacts on major-street le... more This research aimed to develop a methodology for analyzing the platoon impacts on major-street left-turn (MSLT) delay at two-way stop-controlled intersections. The main idea was to use a microscopic simulation tool to simulate different platoon scenarios in opposing through traffic and then to apply regression models to capture the impacts of platoons on the delay of MSLT. Two platoon variables were adopted as a simplification of the complex platoon scenarios to make analysis of the platoon effects on MSLT delay practical. The first two steps were to build simulation models for real-world unsignalized intersections and simulate scenarios with a combination of various factors related to platoons in VISSIM simulation. The models were calibrated with field data before simulation started. The next step was to define, derive, and calibrate two platoon variables for describing the duration and intensity of platoon arrivals in the opposing through traffic. This process effectively simplifi...
This paper presents an overview of the concept and features of the CORSIM traffic simulation prog... more This paper presents an overview of the concept and features of the CORSIM traffic simulation program and the TSIS package that provides an integrated, user-friendly interface and environment for executing CORSIM. The new functions and feature of CORSIM and TSIS in the most ...
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