Authors: Jie Yu, Yue Lie, and Xiaoguang Yang
Conference: 2008 TRB Annual Meeting
Type: Accepted for Presentation
Abstract:
Choosing proper locations of urban transit hubs has always been one of the critical concerns facing urban transportation planning agencies in China. This study proposes a mixed integer optimal location model for urban transit hubs, with the objective to minimize the demand-weighted total travel time, when explicitly taking into account Traffic Analysis Zones (TAZs) as demand origins or destinations in a target urban area. An Integer Non-linear Programming (INLP) reformulation was developed to significantly reduce the number of variables. Bilinear constraints in the proposed INLP formulation were then re-modeled into linear functions to ensure global optimal solutions obtained. The model was successfully applied to optimize the hub locations in Suzhou Industrial Park, China, with the result of significantly improved system performance. The impacts of several critical factors, such as the number of hubs and the travel time discount coefficient on the system performance are also investigated.

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Authors: Jie Yu, Yue, Liu, and Gang-Len Chang
Journal: ASCE Journal of Infrastructure Systems
Abstract:
This paper presents a robust multi-criteria model for prioritizing highway safety improvement projects, in which a set of criteria related to the project’s technical, economic, social and environmental impacts are properly weighted in consideration. The proposed model features an analytical hierarchy process (AHP) framework to tackle the multi-criteria decision making problem. Different from the conventional AHP, this paper adds a fuzzy scale level between the criteria level and the alternative level which offers the advantage of preventing the vagueness and uncertainty on judgments of the decision-maker(s). Such a unique modeling feature is further embedded with a nonlinear optimization formulation to maximize the consistency in pair-wise comparison and weight estimation for each criterion. Case study results reveal that the proposed model is efficient not only for selecting the most suitable project for a specific site, but also for determining the priorities for implementation those suitable projects among multiple sites given the budget constraint. Comparative study between the proposed model and the existing ranking methods has also indicated its capability to capture the comprehensive impacts of all contributory factors which have been neglected by most existing approaches during the safety project selection process. The clarity of model inputs, ease of synthesizing the final score of each candidate project, and the interpretation of results with respect to different selection criteria offer its best potential to be used as an effective tool for highway infrastructure manager and transportation authorities to assess and refine the highway safety improvement investments.

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Authors: Yue Liu, Gang-Len Chang, and Jie Yu
Journal: IEEE transaction on Vehicular Technology
Abstract:
This study presents an integrated model and its solution algorithm for freeway corridor control during incident management. With a parallel arterial as the detour route, the proposed model aims to produce the optimal diversion rates from the freeway mainline to relieve the congestion at the incident segment, and concurrently adjust signal timings at the arterial intersections to best accommodate the detour traffic. Different from previous studies, the presented model and algorithm have the following two critical features: (1) modeling explicitly the evolution of detour traffic along the ramps and surface streets with a set of dynamic network flow formulations so as to capture the local bottlenecks caused by demand surge due to diversion operations, and to properly set the responsive signal timing plans; and (2) developing a multi-objective optimization framework to maximize the utilization of the available corridor capacity via detour operations, but not to incur excessive congestion on the arterials and ramps. This study employs a Genetic Algorithm (GA) based heuristic to efficiently yield the reliable solution depending on decision maker’s preference. Extensive numerical tests on a segment along the I-95 corridor with its neighboring arterials have demonstrated the potential of the developed model for integrated freeway corridor control.

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