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.
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.
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.
Authors: Woon Kim, Hyeonmi Kim, and Gang-Len Chang
Conference: Transportation Research Board, 2015
Abstract: This study proposed a general framework of real-time emergency response operations for highway networks experiencing a high frequency of concurrent traffic emergency events. The proposed system consists of three principal models, working collectively for estimating the probabilities of event occurrences, projecting the incident clearance time, and optimizing the location and coverage of available response units. The system is designed to assist responsible agencies in assessing the need to relocate available incident response units in real time operations, based on the available resources and detected traffic information. The empirical evaluation results showed that the dynamic real-time dispatch strategy can outperform the static dispatch and state-of-the-practice patrolling strategies with respect to minimizing the network-wide delay induced by events and waiting times of vehicles involved in the events for response.
Authors: Yang (Carl) Lu and Dr. Gang-Len Chang
Conference: Transportation Research Board, 2015
Abstract: Due to the apparent capacity difference between Hsuehshan tunnel and its connected roadway segments, identifying the optimal activation time for available control strategies has emerged as a critical issue. This study presents an exploratory system that integrates an existing macroscopic model with a dynamic monitoring function that serves as the basis to guide the selection of a new set of parameters when the traffic condition within the tunnel is evolving into the unstable state. Using one year of field data, our experimental results show the promising properties of the system which can serve as the basis for guiding the activation of the control strategies
Authors: Chien-Lun Lan and Gang-Len Chang
Conference: Transportation Research Board, 2015
Abstract: Scooters are one of the primary transportation modes in many developing countries, but design guidelines and software for arterial signals accommodating heavy scooter-vehicle mixed flows are still
in their infancy. Traffic professionals often have no choice but to apply existing models that cannot address scooters’ complex maneuvers. This study conducts field observations of the mixed traffic flow from their discharging to the formation of stop queues. Based on the statistical analysis results, this study develops a series of formulations to describe the behavior of mixed traffic flows. The developed models are evaluated and
confirmed to be reliable to serve as the basis for designing arterial control plans.
Authors: Hyeonmi Kim, Woon Kim, Gang-Len Chang and Steve M. Rochon
Conference: Transportation Research Board, 2014
Abstract: This study presents a model for optimizing the deployment locations of emergency response units. Unlike most existing studies, the proposed model is designed to assign the available units to minimize the total delay caused by incidents, rather than just to minimize their average response times. The proposed model with the Maryland incident data outperforms both the popular p-median model and the current practice. Extensive sensitivity analyses with respect to various traffic volumes and incident frequencies have also confirmed the superior performance of the proposed model with respect to minimizing the total delay caused by incidents.
Authors: Ying Liu, Pei-Wei Lin, Xiaorong Lai, Gang-Len Chang, and Alvin Marquess
Conference: Transportation Research Board 85th Annual Meeting, 2005
Abstract: The paper presents the framework and field application of a simulation-based on-line system for travel time prediction. The proposed system features its design to contend with most critical issues associated with real-time operations, which includes: estimation of missing volumes, detection of incidents, data filtering, and computation of traffic volumes over the projected time intervals so as to activate the simulation function. The proposed system was deployed over two routes of 30 miles between Salisbury and Ocean City, based on a total of 10 detectors. The preliminary application results clearly indicate that, with a proper integration the proposed system offers a cost-effective tool for real-time travel time predictions.
Authors: Pei-Wei Lin, Nan Zou, and Gang-Len Chang
Conference: The 83rd Annual meeting of the Transportation Research Board, Jan., 2004
ABSTRACT: This paper presents a system that integrates the discrete choice model with a rule-based supplemental module for estimating the duration of a detected incident. The entire system is developed with the archived incident information in Year 2001 from Maryland State Highway Administration, and tested with the Year 2002 incident data. The primary function of the embedded discrete model is to estimate those incidents having durations less than 60 minutes. For severe incidents that may last more than one hour, the system will employ a rule-based supplemental module constructed with information from previous incident management to perform the estimation. With such a system, the control center operators can estimate the potential impact of a detected incident, and select proper real-time incident management strategies, such as detour operations or ramp closure.
Antalya Escort Bayanlar
Authors: Nan Zou, Jianwei Wang, and Gang-Len Chang
Conference: 2007′ World Congress on ITS, Beijing in China
Status: Presented
Abstract: This study develops a hybrid model that can reliably estimate travel times on freeways with sparsely distributed detectors having the spacing of more than one mile. The developed model, which includes a clustered linear regression model as the main component and a supplemental enhanced trajectory-based model, can effectively capture impacts of various geometric features, such as ramps and merging lanes, and different traffic patterns on the variability of travel times. The experimental results based on a field demonstration on a 25-mile stretch of I-70 eastbound with 10 detectors have demonstrated the promising properties of the developed model under various congestion levels.