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.
Authors: Yongjie Lin, Xianfeng Yang, Gang-Len Chang, and Nan Zou
Conference: 92th TRB Annual Meeting in 2013
Abstract: This paper presents a transit signal priority (TSP) model designed to consider the benefits of both bus riders and all intersection passenger car users. The proposed strategy, mainly for headway-based bus operations, offers the responsible agency a reliable way to determine the optimal green extension or red truncation duration in response to multiple bus priority requests from different routes. The control objective is to minimize bus passenger waiting time at the downstream bus stop while ensuring that the delays for all passengers are not increased. Using the field data from Jinan, China, the proposed strategy has shown its promise in reducing the bus passenger waiting time and the total intersection delay. Our further exploration with simulation experiments for sensitivity analysis has also found that TSP will be most effective if the ratio between bus and passenger volumes exceeds the threshold of 2 percent.
Download (Transit_Priority_Strategies_for_Multiple_Routes_under_Headway_based_Operations.pdf)
Authors: Seonyeong Cheong, Saed Rahwanji, and Gang-Len Chang
Conference: The 11th International IEEE Conference on Intelligent Transportation System, October 2008 in Beijing, China
Status: Presented
Abstract: This research is aimed to evaluate and compare the operational performance of three unconventional intersections: Continuous Flow Intersection (CFI), Parallel Flow Intersection (PFI) and Upstream Signalized Crossover (USC). For this purpose, various experimental designs, including traffic conditions, geometric features and signal plans, were set and the average delays were compared for movements of through-only traffic and left-turn-only traffic. From the results of analysis, all three unconventional intersections outperformed conventional one and among the unconventional intersections, CFI outperformed the others except for some traffic conditions. In the balanced traffic condition scenario, at the low traffic volume level, the average delays of through traffic for PFI were smaller than that of CFI and very similar at the moderate traffic volume level. And this research showed one possibility that the average delays of left-turn-only traffic at PFI will be closer to that of CFI as the traffic volume increases. In the unbalanced traffic condition scenario, under some traffic conditions, PFI outperformed CFI or showed very similar average delay with CFI. And generally, there were not much difference in the average delays between CFI and PFI as compared with that between CFI and USC under the experimental traffic conditions of this research. Considering the accessibility and land use problems of CFI, PFI is a good alternative to reduce the average delays, which is comparable to CFI, and as well reduce the property impact and cost.
Authors: Xianfeng Yang, Yao Cheng, Gang-Len Chang
Conference: ITS world congress, 2014
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. Hence, an accurate queue estimation model can help the traffic engineers to select proper control strategy to mitigate queue spillback at off-ramps. In responds to such a need, this study presents a queue estimation system using dual-zone detectors, where each detector can provide two detection zones. Particularly, the short detection zones are used to count traffic flow rates and the information from long detection zone can indicate the presence of traffic queues. With respect to different congestion levels, the off-ramp queue may be fully discharged during the green time or not. Therefore, this study has developed two queue estimation models for each condition. Based on the field data from the freeway interchange in Zhubei, Taiwan, this study has conducted extensive simulation experiments, and demonstrated the effectiveness of the proposed system on off-ramp queue estimations.
Download (Real-Time-Traffic-Queue-Length-Estimation-at-Freeway-Off-ramps.pdf)