Authors: Xiaorong Lai, Minseok Kim, Gang-Len Chang, and Saed Rahwanji
Conference: The PTV America Users Group Meeting 2007
Abstract:
Rising as a new alternative to relieve arterial congestion, the UAID concept generally attempts to enhance operational efficiency at major arterial intersections by reducing the negative impacts of turning movements through various innovative intersection designs. General principles of operation and management strategies of the UAID include: 1) an emphasis on throughtraffic movements along the arterial, 2) a reduction in the number of signal phases (e.g., left-turn arrow phases), and 3) a reduction in the number of intersection conflict points. As a collaborative research effort among the University of Maryland at College Park, Maryland State Highway Administration, and Parsons Brinckerhoff Inc., the knowledge base web interface (https://attap.umd.edu/uaid.php ) has been built to help traffic engineers, community planners, and elected officials to consider the UAID as a feasible solution for relieving arterial congestion and to select proper unconventional design schemes given
actual traffic patterns.
Authors: Pei-Wei Lin (pwlin@wam.um.edu) and Gang-Len Chang
Conference: the 9th International Conference on Applications of Advanced Technology in Transportation, Chicago, IL
Date: August 13-16, 2006
Abstract:
This study presents a robust algorithm that can deal with the incomplete volume information so as to significantly improve the estimation accuracy. To tackle the inevitable measurement data error or only partially available information, the proposed robust algorithm converts each model input data into one interval with its upper and lower bounds best approximated from historical data or/and prior knowledge. A simulated system, the I-95 freeway corridor between I-495 and I-695, has been created to generate example data and to perform the numerical evaluation of the developed robust algorithm.
Authors: Ying Liu and Gang-Len Chang
Conference: The 9th international conference on Applications of Advanced Technologies in Transportation Engineering, 2006
Abstract:
This study presents a new approach for estimating travel time information along freeway corridors, which experience recurrent congestions but have only a limited number of available detectors due to budget constraints. The proposed iterative estimation procedure, based on a set of empirically calibrated regression models, intends to rebuild the relations between travel times and accumulated flows within each segment of the target freeway corridor. To evaluate the effectiveness of the proposed methodology, this study has conducted extensive numerical experiments with simulated data from a CORSIM simulator. Experimental results under various traffic volume levels have revealed that the proposed method offers a promising property for use in travel time estimation based on sparsely distributed sensors.
Authors: Ying Liu, Xiaorong Lai, Gang-len Chang
Conference: the 8th International Conference on Applications of Advanced Technology in Transportation, Chicago, IL
Date: May 26-28, 2004
Abstract:
This paper has investigated critical issues associated with Optimal Detector Locations for OD matrix estimation, including a discussion of limitations embedded in existing models and heuristic algorithms. Grounded on the core methodology of existing literature (Yang, 1998), this paper has proposed a heuristic algorithm for identifying the optimal set of detector locations under a given budget constraint for effective OD matrix estimation. The algorithm tries to simultaneously optimize OD coverage, net OD flow intercepted and link-OD flow fraction. Our numerical experiment results have indicated that the proposed algorithm is quite promising for potential applications.
Authors: Yue Liu, Gang-Len Chang, Ruihua Tao, Eric Tabacek, and Thomas Hicks
Conference: Application of Advanced Technology in Transportation (AATT), Chicago, IL
Date: August 13-16, 2006
Abstract:
Understanding the response and acceleration/deceleration rate of driving populations to a yellow phase is essential for estimating the dynamic distribution of intersection dilemma zones. This paper presents a video-based method for measuring driver responses during a yellow phase, including their speed evolution profile, acceleration/deceleration rate, and the approximate reaction time. Such information is critical for understanding the spatial distribution of dynamic dilemma zones and the design of strategies to improve intersection safety. This paper details the key components of the proposed system and the systematic procedures for both field operations and data extraction. The results of a rigorous validation with an advanced experimental vehicle provided by Nissan are also reported in this paper.
Authors: Nan Zou and Jianwei Wang
Conference: Application of Advanced Technology in Transportation (AATT), Chicago, IL
Date: August 13-16, 2006
Abstract:
This paper presents a video-based method for evaluating and validating volume and speed data collected with traffic detectors. Assessing the detector data reliability is a critical task for all Intelligent Transportation Systems (ITS). Their performance will be significantly impacted by the data quality. Most existing studies mainly use volume as the only variable for evaluating the detector quality. A cost-efficient and rigorous method that can concurrently evaluate both volume and speed from the detectors is not available yet. The video-based method presented in this study is both cost-efficient and sufficiently reliable for evaluating detector data for ITS system operations. For example, the performance of a travel time prediction system is very sensitive to the quality of the detector data. This paper will mainly detail the key features of the proposed system and its application in a case study of RTMS detector data on I-70 corridor in Maryland.
Authors: Xianfeng Yang, Gang-Len Chang, Saed Rahwanji
Conference: 92th TRB Annual Meeting in 2013
Unconventional Design: DDI
Purpose:
- Developed a set of planning models for DDI geometry design based on the estimated maximal queue length for each link.
- Developed a signal optimization plan for DDI to achieve signal progressions.
Abstract:
As one of the most popular unconventional interchange designs, diverging diamond intersection (DDI) has received increasing attention over the past decade. This study, responding to the needs, has produced a reliable and convenient system for traffic engineers to perform operational analysis of DDI. The entire system comprises three modules for planning analysis, signal optimization, and operational evaluation. At the planning stage, this system presents a set of empirical equations for engineers to compute the overall interchange delay and identify the potential queue spillback locations in a DDI design. The second module aims to provide the optimal signal plans to prevent the potential queue blockage. This module is unique in its consideration of the interdependent relations between queues at a DDI’s closely-spaced intersections, and the impacts by both geometrical constraints and traffic volumes. Given the traffic volumes, geometrical features, and signal timings, the system’s third module provides users to link a VISSIM-based simulation model to estimate the resulting traffic queues and interchange delays. Numerical analysis with four real-world DDI designs has revealed the effectiveness of the proposed system.
Authors: Zichuan Li, Gang-Len Chang, Suhasini Natarajan
Conference: the 11th International IEEE Conference on Intelligent Transportation System, October 2008 in Beijing, China
Status: Presented
Abstract:
This study presents a mixed integer model for an integrated control between off-ramp and arterial traffic flows. The proposed study intends to minimize the queue spillback from off-ramp to the freeway mainline that may significantly degrade the performance quality of the entire freeway system. In this study, the Cell Transmission Model (1, 2) is employed to capture the traffic propagation on both freeway an surface streets, and to capture the interactions between those two types of flows within the target control boundaries. An efficient solution method based on Genetic Algorithm is provided along with a numeric case study to demonstrate the benefit of this proposed model.
Authors: Xin Zhang and Gang-Len Chang
Conference: TRB 2010 Annual Meeting, January 12, 2010
Status: Presented
Abstract:
This paper presents an integrated model for design of signal plans for massive mixed pedestrian-vehicle flows within the evacuation zone. The proposed model with its embedded formulations for pedestrians and vehicles in the same network can effectively take into their potential conflicts during the evacuation, and generate the optimal routing strategies for guiding evacuees moving toward either the pick-up locations or their parking areas. The core formulations is based on the cell-transmission concept, but the proposed model has been enhanced with the notion of sub cells proposed mainly to capture the complex movements in the pedestrian flows so that it can concurrently optimize both the signals for pedestrian-vehicle flows and the movement directions for evacuees. An illustrating example concerning the evacuation around the M&T stadium area has been used to demonstrate the promising properties of our model.
Authors: Xin Zhang, Gang-Len Chang, and Alvin Marquess
Abstract: Evacuating large municipal areas during emergencies in an efficient manner is one of the critical concerns of most responsible management agencies. Previous studies focus mainly on strategic evacuation plans or controls for the passenger cars, giving inadequate attention to those pedestrians community with transit systems or other modes especially in metropolitan areas. This study has developed an evacuation planning module for pedestrians in Washington D.C. and integrates it with the system developed for passenger-car evacuation. The proposed module first guides people to the nearest metro-stations, and then applies the knowledge-based method to choose proper evacuation routes for shuttles to pick up evacuees. It also includes the plans for guiding pedestrians to the nearest evacuation route, and for dispatching shuttles need for their evacuation.