Authors:  Xianfeng Yang, Gang-Len Chang, Yang Lu, and Saed Rahwanji
Conference:  92th TRB Annual Meeting in 2013

Abstract:
Despite the increasing use of continuous flow intersections (CFI) to contend with the congestion caused by heavy through and left-turn traffic flows, a reliable and convenient tool for the traffic community to identify potential deficiencies for CFI’s geometry design are not available yet. This is due to the unique geometric feature of CFI which comprises one primary intersection and several crossover intersections. The interdependent relation between the traffic delays and queues at a CFI’s five closely-spaced intersections cannot be fully captured with the existing analysis models developed for conventional intersections. In response to such a need, this study presents a comprehensive analysis for the overall CFI delay, identifies the potential queue spillback locations, and develops a planning framework for CFI’s geometry designs. To facilitate the application of our proposed models, this paper also includes a case study of a CFI at intersection MD 4 and MD 235 conducted by Maryland State Highway Administration.

Download (Yang_TRB_2011.pdf)

Authors: Xin Zhang and Gang-Len Chang

Authors: Xin Zhang and Gang-Len Chang
Conference:  90th TRB Annual Meeting in 2011
Abstract: In metropolitan areas, a potentially large number of pedestrians depend either on transit or other modes for evacuation, or need to walk a distance to access their passenger cars. In the process of
approaching some designated pick-up points for evacuation, the massive number of pedestrians may incur tremendous burden to the vehicles on the roadway network. Thus, an effective coordination between the
vehicle and pedestrian flow during the multi-modal evacuation process shall be devised. This paper presents an integrated linear model for design of routing plans for massive mixed pedestrian-vehicle flows
within the evacuation zone. The proposed model integrating the pedestrian and vehicle networks 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. An illustrating example concerning the evacuation around the M&T stadium area has been presented and seems to indicate promising properties to address the complex interactions between vehicle and pedestrian flows within the evacuation zone. Results of simulation experiments clearly indicate that the failure to account for the conflict movement will yield unrealistic plans that can’t be implemented during the actual evacuation process.

Download (Xin_Mixed_Flow_Optimization_Linear_TRB_2011.pdf)

Authors: Woon Kim, Yue Liu and Gang-Len Chang
Conference:  90th TRB Annual Meeting in 2011
Abstract:
This paper presents a detour decision model for freeway non-recurrent congestion management, based on the results of extensive simulation experiments and operational guidelines for highway agencies. The proposed model offers a reliable and effective tool for responsible traffic operators to make consistent detour decisions in response to a detected incident. Numerical results clearly indicate that a timely and well justified detour operation can yield substantial benefits to both the driving populations and the entire community.

Download (Woon_TRB_2011.pdf)

Authors: Woon Kim and Gang-Len Chang
Conference:  ITS World Congress 2010
Abstract:
This paper presents a detour decision model for freeway non-recurrent congestion management, based on the results of extensive simulation experiments and operational guidelines for highway agencies. The proposed model offers a reliable and effective tool for responsible traffic operators to make consistent detour decisions in response to a detected incident. Numerical results clearly indicate that a timely and well justified detour operation can yield substantial benefits to both the driving populations and the entire community.

Download (woon_ITS_World_Congress_2010.pdf)

Authors: Woon Kim, Gang-Len Chang, Steven M. Rochon
Conference: The 15th World Congress on Intelligent Transport Systems, New York, 2008
Abstract:
This paper presents a methodology for developing a model for estimating and predicting incident duration and identifying variables influencing the incident duration in the state of Maryland. The incident information from years 2003 to 2005 from the Maryland State Highway (MDSHA) database is used for model development, and year 2006 for the model validation. Classification Trees (CT) were used for a preliminary analysis to understand the influence of the variables associated with an incident. Based on the findings from CT, this study employed the Rule-Based Tree Model (RBTM) to develop the primary prediction model. The overall confidence for the estimated model was over 80% with several remarkable findings regarding the associations between factors and incident duration. Although the estimated results from RBTM are quite acceptable, supplemental models along with better quality database are required to improve the prediction accuracy for the duration of a detected incident.

Download (Woon_2.pdf)

Authors: Woon Kim, Suhasini Natarajan, and Gang-Len Chang
Conference: The 11th International IEEE Conference on Intelligent Transportation System, October 2008 in Beijing, China.
Status: Presented
Abstract:
This paper presents a methodology for developinga model to identify the variables influencing incident duration to estimate and predict incident duration in the state of Maryland. The incident information from years 2003 to 2005 from the Maryland State Highway (MDSHA) database was used for model development, and year 2006 for model validation. Classification Trees (CT) were employed for a preliminary analysis to understand the influence of the variables associated with an incident. Based on the findings from CT, this study employed the Rule-Based Tree Model(RBTM) to develop the primary prediction model. The overall confidence for the estimated model was over 80% with several remarkable findings regarding the association between the identified factors and incident duration. Although the estimated results from RBTM were quite acceptable, in cases where RBTM did not provide incident duration within a desirable short range, a discrete choice model was developed as a supplemental model. It is deduced that supplemental models along with better quality database are required to improve the prediction accuracy of the duration of a detected incident.

Download (Woon_1.pdf)

Authors: Jianwei Wang, Nan Zou, and Gang-Len Chang
Conference: 2008 TRB Annual Meeting
Status: Presentation
Abstract: As reported in the literature for Intelligent Transportation System (ITS) applications with traffic detectors, various missing data patterns are frequently observed in such systems and may dramatically degrade their performance. This study presents two imputation approaches for contending with the missing data issues in travel time prediction. The first model is based on the concept of multiple imputation technique to directly predict the travel times under various missing data patterns. The second model that serves as the supplemental component is to estimate the missing detector values using neighboring detector data and historical traffic patterns. Both models have been incorporated with reliability indicators so as to assess the quality of imputed data and its applicability for use in prediction. The numerical example based on 10 roadside detectors on I-70 in Maryland has demonstrated that both developed models outperformed existing methods and offers the potential for field implementation.

Download (Wang_1143.pdf)

Authors: Minseok Kim, Xiaorong Lai, Gang-Len Chang and Saed Rahwanji
Conference: 2007′ IEEE Conference on Intelligent Transportation Systems, Seattle, WA
Status: Presented
Abstract:
This paper addresses initiative works done in the state of Maryland in order to provide a clearing house for unconventional arterial intersection designs (UAIDs) and apply their concepts to selected locations. As a collaborative research effort among the University of Maryland at College Park, Maryland State Highway Administration (MSHA), and Parsons Brinckerhoff Inc., a knowledge base web interface 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 appropriate unconventional design schemes given actual traffic patterns. A great number of statistics on visits and page views show the beneficial effect of the website. The MSHA has also been active in adopting unconventional design concepts at local intersections that incurred operational or safety problems. This paper summarizes four case studies that have been conducted for those locations and treated relatively new UAID concepts, including: 1) superstreet intersection, 2) continuous flow intersection, 3) center turn overpass, and 4) roundabout at high speed approaches. Results of these case studies indicate that the unconventional intersection designs have promise of enhancing not only operational efficiency but also safety along the arterial.

Download (UAID_IEEEITS2007.pdf)

Authors: Xianfeng Yang, Yao Cheng, Gang-Len Chang
Conference: Transportation Research Board, 2015
Abstract:  Congestion at the downstream of a freeway off-ramp often propagates the traffic queue to the mainline, and thus reduces the freeway capacity at the interchange area. To prevent the potential queue spillback, this study proposes a two-stage control model to optimize the signal plans on an off-ramp connected arterial. The first-stage of the model aims to optimize the green splits with a specified off-ramp queue length constraint. The second stage of this model is focused on the coordination of both off- ramp flows and local through traffic.

Download (trb2015_Signal.pdf)