Dr Xiaobo Qu joins the School of Civil and Environmental Engineering, University of Technology Sydney (UTS) as a Senior Lecturer (Transport Engineering) since July 2016. Prior to his UTS appointment, he was a Senior Lecturer (Transport Engineering) in Griffith School of Engineering, Griffith University. Dr Qu obtained his PhD, Master's degree, Bachelor's degree from the National University of Singapore, Tsinghua University, and Jilin University, respectively.
Dr Qu's research is focused on practically improving transport safety, efficiency, equity, and sustainability through traffic flow and network modelling and optimisation. He has authored or co-authored over 40 journal articles published by leading international peer reviewed transportation journals such as Transportation Research Part A, Part B, Part C, Part E, Accident Analysis and Prevention, ASCE - Journal of Transportation Engineering, and Risk Analysis. He is a recipient of Ministry of Transport (Singapore) Minister's Innovation Award in 2009, President's Graduate Fellowship (Singapore) in 2010-2011, ASCE - Journal of Transportation Engineering Outstanding Reviewer Award in 2013, Griffith University Pro-Vice Chancellor Early Career Research Excellence Award in 2015, Griffith University Pro-Vice Chancellor Research Excellence Award (Group Category) in 2015, and EPPM 2015 best paper award.
Dr Qu also has a great passion for teaching profession. From Feb 2012 to June 2016, he has been single-handedly looking after all three transport engineering subjects in Griffith School of Engineering, Griffith University. His teaching performance has always been among the best in Griffith School of Engineering (average teaching evaluation = 4.35/5). His teaching has been distinguished by the Griffith University Dean's letter of outstanding in teaching in 2012, Griffith University Dean's Learning and Teaching Commendation in 2014, Griffith University Dean's Learning and Teaching Citation in 2015, nominee of lecturer of the year (finalist) in 2015, and three peer reviewed artciles in Learning & Teaching scholarship. Dr Qu has supervised two PhD students towards completion as their primary supervisor, and is currently supervising four PhD students as their primary supervisor. Please click here for details.
Can supervise: YES
Representative Publications (+: PhD students or academics under my supervision)
15. Zhou, M., Qu, X., and Jin, S., 2016. On the impact of cooperative autonomous vehicles in improving freeway merging: An modified intelligent driver model based approach. IEEE Transactions on Intelligent Transportation Systems. 10.119/TITS.2016.2606492.
14. Wang, S., and Qu, X., 2016. Station choice for Australian commuter rail lines: equilibrium and optimal fare design. European Journal of Operational Research, http://dx.doi.org/10.1016/j.ejor.2016.08.040.
13. Qu, X., Wang, S., and Zhang, J., 2015. On the fundamental diagram for freeway traffic: A novel calibration approach for single-regime models. Transportation Research Part B, 73, 91-102.
12. Ren, L. +, Qu, X., Guan, H., Easa, S., and Oh, E., 2016. Evaluation of Roundabout Capacity Models: An Empirical Case Study. Journal of Transportation Engineering – ASCE, DOI: 10.1061/(ASCE)TE.1943-5436.0000878.
11. Jin, S. +, Qu, X., Xu, C., Ma, D., and Wang, D., 2015. An improved multi-value cellular automata model for heterogeneous bicycle traffic flow. Physics Letters A, 379(39), 2409-2416.
10. Kuang, Y. +, Qu, X., and S. Wang, 2015. A tree-structured crash surrogate measure for freeways. Accident Analysis and Prevention, 77, 137-148.
9. Jin, S. +, Qu, X., Zhou, D., Xu, C., Ma, D., and Wang, D., 2015. Estimating Capacity and Bicycle Equivalent Units for Electric Bicycles on Shared Bicycle Paths. Transportation Research Part A, 77, 225-248.
8. Wang, S., Qu, X., and Yang, Y., 2015. Estimating containers' value of transit time for planning liner shipping services. Transportation Research Part A, 78, 298-308.
7. Qu, X., Yang, Y., Liu, Z., Weng, J., and Jin, S., 2014. Potential crash risks of expressway on-ramps and off-ramps: a case study in Beijing, China. Safety Science, 70, 58-62.
6. Qu, X., Ren, L.+, Wang, S., and Oh, E., 2014. Estimation of entry capacity for single-lane modern roundabouts: A case study in Queensland, Australia. Journal of Transportation Engineering - ASCE, 140(7), 05014002.
5. Meng, Q., and Qu, X., 2013. Bus dwell time estimation at a bus bay: A probabilistic approach. Transportation Research Part C, 36, 61-71.
4. Meng, Q., and Qu, X., 2012. Estimation of vehicle crash frequencies in road tunnels. Accident Analysis and Prevention, 48, 254-263.
3. Qu, X., and Meng, Q., 2012. The economic importance of the Straits of Malacca and Singapore: an extreme-scenario analysis. Transportation Research Part E, 48, 258-265.
2. Li, S., Meng, Q., and Qu, X., 2012. An overview of maritime waterway quantitative risk assessment models. Risk Analysis, 32, 496-512.
1. Qu, X., Meng, Q., and Li, S., 2011. Ship collision risk assessment for the Singapore Strait. Accident Analysis and Prevention, 43, 2030-2036.
Road and transport engineering
Traffic flow theory
Zhen, L, Wang, K, Wang, S & Qu, X 2018, 'Tug scheduling for hinterland barge transport: A branch-and-price approach', European Journal of Operational Research, vol. 265, no. 1, pp. 119-132.View/Download from: UTS OPUS or Publisher's site
© 2017 Elsevier B.V. In a hinterland barge transport system, barges are usually not self-propelled and need to be towed or pushed by tugs. This study investigates a tug-scheduling problem at a seaport that is located at a river mouth and that connects the hinterland ports along the river with the global maritime transportation network. A mixed-integer programming model is proposed to optimize the assignment of barges to tugs as well as the time when the tugs depart from the seaport and go to the hinterland ports. Some properties of the model are also investigated. Moreover, an exact solution method based on a branch-and-price approach is developed to solve the proposed model. Numerical experiments are also conducted to validate the effectiveness of the proposed model and the efficiency of the proposed solution method.
Xu, Z, Wei, T, Easa, S, Zhao, X & Qu, X 2018, 'Modeling Relationship between Truck Fuel Consumption and Driving Behavior Using Data from Internet of Vehicles', COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, vol. 33, no. 3, pp. 209-219.View/Download from: UTS OPUS or Publisher's site
Ghanbarikarekani, M, Qu, X, Zeibots, M & Qi, W 2018, 'Minimizing the Average Delay at Intersections via Presignals and Speed Control', Journal of Advanced Transportation, vol. 2018.View/Download from: UTS OPUS or Publisher's site
© 2018 Mina Ghanbarikarekani et al. Urban intersections have been well recognized as bottlenecks of urban transport systems. It is thus important to propose and implement strategies for increasing the efficiency of public and private transportation systems as a whole. In order to achieve this goal, an additional signal could be set up near the intersection to give priority to buses through stopping vehicles in advance of the main intersection as a presignal. It has been increasingly popular in urban cities. While presignals indeed reduce the average delay per traveler, they cause extra stops of private vehicles, which might compromise the overall efficiency, safety, and sustainability. This paper aims to propose a model to improve presignals by reducing the vehicles' number of stops behind the presignals. By applying the method, vehicles would be able to adjust their speed based on traffic conditions as well as buses' speed and approach. Numerical analyses have been conducted to determine the conditions required for implementing this method.
Zhou, M, Qu, X & Jin, S 2017, 'On the Impact of Cooperative Autonomous Vehicles in Improving Freeway Merging: A Modified Intelligent Driver Model-Based Approach', IEEE Transactions on Intelligent Transportation Systems, vol. 18, no. 6, pp. 1422-1428.View/Download from: UTS OPUS or Publisher's site
Transport researchers and practitioners have long been seeking capable solutions to deal with the traffic oscillations caused by freeway merging. Although existing approaches based on ramp metering have improved the overall efficiency of on-ramps, their performance is still far below the theoretical capacity. The recently proposed detecting technology of autonomous vehicles (AVs) provides an alternative for maximizing the merging efficiency by developing and using appropriate controllers for AVs. In this paper, we develop a cooperative intelligent driver model in order to examine the system performance under different proportions of AVs. The results show that, with a proper vehicle-to-vehicle controlling mechanism, an increasing percentage of AVs will reduce the total travel time and smooth traffic oscillations.
Wang, S & Qu, X 2017, 'Station choice for Australian commuter rail lines: Equilibrium and optimal fare design', European Journal of Operational Research, vol. 258, no. 1, pp. 144-154.View/Download from: UTS OPUS or Publisher's site
© 2016 Elsevier B.V. We examine how park-and-ride commuters living along a rail line compete for seats when they travel to their workplace in Australian metropolitan areas. First, we prove that at user equilibrium in which each commuter minimizes her expected travel cost, there exists one station on the rail line at which some commuters could find a seat and the others have to stand; all of the commuters boarding at its upstream stations have seats and all of the commuters boarding at its downstream stations must stand in the train. We derive a solution algorithm for obtaining a user equilibrium, which involves solving an equation with only one variable. We demonstrate that more than one user equilibrium may exist. Second, we examine the system optimal station choice that assumes all of the commuters cooperate and minimizes their total travel cost. An analytical solution approach is proposed based on the structure of the problem. Third, we investigate the optimal train fare design that leads to the system optimal station choice. We prove that the optimal train fare satisfies: there exists a particular train station that has some seats and the train is full after this station. All of its upstream stations have the same fare, which is higher than or equal to the fare of this particular station; and all of its downstream stations have the same fare, which is lower than the fare of this particular station.
Wang, K, Wang, S, Zhen, L & Qu, X 2017, 'Cruise service planning considering berth availability and decreasing marginal profit', Transportation Research Part B: Methodological, vol. 95, pp. 1-18.View/Download from: UTS OPUS or Publisher's site
© 2016 Elsevier Ltd This paper addresses a decision problem on planning cruise services for a cruise ship so as to maximize the total profit during a planning horizon. The service is a sequence of ports (harbor cities) that the cruise ship visits. In this decision problem, the constraint about the availability of berths at each port is taken into account. In reality, if a cruise service is executed by the ship repeatedly for several times, the profit earned by the cruise service in each time decreases gradually. This effect of decreasing marginal profit is also considered in this study. We propose a nonlinear integer programming model to cater to the concavity of the function for the profit of operating a cruise service repeatedly. To solve the nonlinear model, two linearization methods are developed, one of which takes advantage of the concavity for a tailored linearization. Some properties of the problem are also investigated and proved by using the dynamic programming (DP) and two commonly used heuristics. In particular, we prove that if there is only one candidate cruise service, a greedy algorithm can derive the optimal solution. Numerical experiments are conducted to validate the effectiveness of the proposed models and the efficiency of the proposed linearization methods. In case some parameters needed by the model are estimated inexactly, the proposed decision model demonstrates its robustness and can still obtain a near-optimal plan, which is verified by experiments based on extensive real cases.
Qu, X, Yi, W, Wang, T, Wang, S, Xiao, L & Liu, Z 2017, 'Mixed-Integer Linear Programming Models for Teaching Assistant Assignment and Extensions', Scientific Programming, vol. 2017.View/Download from: UTS OPUS or Publisher's site
© 2017 Xiaobo Qu et al. In this paper, we develop mixed-integer linear programming models for assigning the most appropriate teaching assistants to the tutorials in a department. The objective is to maximize the number of tutorials that are taught by the most suitable teaching assistants, accounting for the fact that different teaching assistants have different capabilities and each teaching assistant's teaching load cannot exceed a maximum value. Moreover, with optimization models, the teaching load allocation, a time-consuming process, does not need to be carried out in a manual manner. We have further presented a number of extensions that capture more practical considerations. Extensive numerical experiments show that the optimization models can be solved by an off-the-shelf solver and used by departments in universities.
Wang, S, Qu, X, Wang, T & Yi, W 2017, 'Optimal container routing in liner shipping networks considering repacking 20 ft containers into 40 ft containers', Journal of Advanced Transportation, vol. 2017.View/Download from: UTS OPUS or Publisher's site
© 2017 Shuaian Wang et al. The volume of a 40 ft container is twice as large as that of a 20 ft container. However, the handling cost (loading, unloading, and transshipment) of a 40 ft container is much lower than twice the corresponding handling cost of two 20 ft containers. Enlightened by this observation, we propose a novel container routing with repacking problem in liner shipping, where two 20 ft containers can be repacked to a 40 ft container in order to reduce the handling cost. We develop a mixed-integer linear programming model that formulates the routing decisions and the repacking decisions in a holistic manner. An illustrative example is reported to demonstrate the applicability of the model. Results show that the benefit of repacking is the most significant when containers are transshipped several times.
Wang, S, Liu, Z & Qu, X 2017, 'Weekly container delivery patterns in liner shipping planning models', Maritime Policy and Management, vol. 44, no. 4, pp. 442-457.View/Download from: UTS OPUS or Publisher's site
© 2017 Informa UK Limited, trading as Taylor & Francis Group. This paper addresses a fundamental question related to nearly all container liner shipping planning models: whether the implicit assumption of identical container delivery pattern every week is valid in a situation of identical shipping services and identical cargo demand every week. We prove that when the number of containers transported from one port to the next is formulated as a continuous variable, the resulting mathematical model with an identical container delivery pattern is equivalent to the model with general container delivery patterns which can be different in different weeks. When the number of containers transported is formulated as an integer variable, the model with an identical container delivery pattern is not equivalent to the model with general container delivery patterns. However, the difference between the optimal objective values of the two models is negligible for practical applications. In sum, little, if not nothing, is lost by assuming an identical container delivery pattern in liner shipping planning models.
© 2017 "IISE". The Cruise Itinerary Schedule Design (CISD) problem determines the optimal sequence of a given set of ports of call (a port of call is an intermediate stop in a cruise itinerary) and the arrival and departure times at each port of call in order to maximize the monetary value of the utility at ports of call minus the fuel cost. To solve this problem, in view of the practical observations that most cruise itineraries do not have many ports of call, we first enumerate all sequences of ports of call and then optimize the arrival and departure times at each port of call by developing a dynamic programming approach. To improve the computational efficiency,we propose effective bounds on the monetary value of each sequence of ports of call, eliminating non-optimal sequences without invoking the dynamic programming algorithm. Extensive computational experiments are conducted and the results showthat, first, using the bounds on the profit of each sequence of ports of call considerably improves the computational efficiency; second, the total profit of the cruise itinerary is sensitive to the fuel price and hence an accurate estimation of the fuel price is highly desirable; third, the optimal sequence of ports of call is not necessarily the sequencewith the shortest voyage distance, especially when the ports do not have a natural geographic sequence.
Kuang, Y, Qu, X & Yan, Y 2017, 'Will higher traffic flow lead to more traffic conflicts? A crash surrogate metric based analysis.', PLoS ONE, vol. 12, no. 8.View/Download from: UTS OPUS or Publisher's site
In this paper, we aim to examine the relationship between traffic flow and potential conflict risks by using crash surrogate metrics. It has been widely recognized that one traffic flow corresponds to two distinct traffic states with different speeds and densities. In view of this, instead of simply aggregating traffic conditions with the same traffic volume, we represent potential conflict risks at a traffic flow fundamental diagram. Two crash surrogate metrics, namely, Aggregated Crash Index and Time to Collision, are used in this study to represent the potential conflict risks with respect to different traffic conditions. Furthermore, Beijing North Ring III and Next Generation SIMulation Interstate 80 datasets are utilized to carry out case studies. By using the proposed procedure, both datasets generate similar trends, which demonstrate the applicability of the proposed methodology and the transferability of our conclusions.
Qu, X, Zhang, J & Wang, S 2017, 'On the stochastic fundamental diagram for freeway traffic: Model development, analytical properties, validation, and extensive applications', Transportation Research Part B: Methodological, vol. 104, pp. 256-271.View/Download from: UTS OPUS or Publisher's site
© 2017 Elsevier Ltd In this research, we apply a new calibration approach to generate stochastic traffic flow fundamental diagrams. We first prove that the percentile based fundamental diagrams are obtainable based on the proposed model. We further prove the proposed model has continuity, differentiability and convexity properties so that it can be easily solved by Gauss–Newton method. By selecting different percentile values from 0 to 1, the speed distributions at any given densities can be derived. The model has been validated based on the GA400 data and the calibrated speed distributions perfectly fit the speed-density data. This proposed methodology has wide applications. First, new approaches can be proposed to evaluate the performance of calibrated fundamental diagr ams by taking into account not only the residual but also ability to reflect the stochasticity of samples. Secondly, stochastic fundamental diagrams can be used to develop and evaluate traffic control strategies. In particular, the proposed stochastic fundamental diagram is applicable to model and optimize the connected and automated vehicles at the macroscopic level with an objective to reduce the stochasticity of traffic flow. Last but not the least, this proposed methodology can be applied to generate the stochastic models for most regression models with scattered samples.
Easa, SM, Qu, X & Dabbour, E 2017, 'Improved pedestrian sight-distance needs at railroad-highway grade crossings', Journal of Transportation Engineering, vol. 143, no. 7.View/Download from: UTS OPUS or Publisher's site
© 2016 American Society of Civil Engineers. This paper presents an improved model for pedestrian crossing time that is used to establish preliminary guidelines for lateral clearance needs on railroad-highway grade crossings. The improved model includes new elements that are lacking in existing models such as pedestrian observation-reaction time, length of pedestrian unit, and safety margin. A general model for the required lateral clearance, that is applicable to any number of tracks on crossings located on horizontal curves or on tangent sections, was developed. The model can be used to determine the required lateral clearance to the right and to the left of the crossing, including maximum lateral clearance, its location, and lateral clearance at a specified location. A comparison of pedestrian crossing sight distance with intersection (vehicle) sight distance shows that lateral clearance needs for pedestrians are not generally satisfied by those currently available for vehicles. The presented design guidelines promote pedestrian safety and should be of interest to highway and railroad professionals.
Zhou, M, Qu, X & Li, X 2017, 'A recurrent neural network based microscopic car following model to predict traffic oscillation', Transportation Research Part C: Emerging Technologies, vol. 84, pp. 245-264.View/Download from: UTS OPUS or Publisher's site
This paper proposes a recurrent neural network based microscopic car following model that is able to accurately capture and predict traffic oscillation. Neural network models have gained increasing popularity in many fields and have been applied in modelling microscopic traffic flow dynamics due to their parameter-free and data-driven nature. We investigate the existing neural network based microscopic car following models, and find out that they are generally accurate in predicting traffic flow dynamics under normal traffic operational conditions. However, they do not maintain accuracy under conditions of traffic oscillation. To bridge this research gap, we first propose four neural network based models and evaluate their applicability to predict traffic oscillation. It is found that, with an appropriate structure and objective function, the recurrent neural network based model has the capability of perfectly re-establishing traffic oscillations and distinguish drivers characteristics. We further compare the proposed model with a classical car following model (Intelligent Driver Model). Based on our case study, the proposed model outperforms the classical car following model in predicting traffic oscillations with different driver characteristics.
Wang, K, Wang, S, Zhen, L & Qu, X 2017, 'Ship type decision considering empty container repositioning and foldable containers', Transportation Research Part E: Logistics and Transportation Review, vol. 108, pp. 97-121.View/Download from: UTS OPUS or Publisher's site
© 2017 Elsevier Ltd This paper addresses a problem of ship type decision considering empty container repositioning and foldable containers, which determines the capacity of ships deployed in a given shipping route at a tactical level and empty container repositioning between ports at an operational level. It considers the use of foldable containers and aims to find under what conditions, a shipping liner needs to use the foldable containers. To solve the problem, we formulate a network flow model with a revised network simplex algorithm, based on which an exact solution approach is designed to determine the optimal ship type.
Qu, X & Mao, G 2017, 'Guest Editorial: Selected Papers from the 23rd ITS World Congress, Melbourne 2016', IET Intelligent Transport Systems, vol. 11, no. 10, pp. 613-614.View/Download from: UTS OPUS or Publisher's site
Bie, Y, Cheng, S, Easa, SM & Qu, X 2016, 'Stop-Line Setback at a Signalized Roundabout: A Novel Concept for Traffic Operations', JOURNAL OF TRANSPORTATION ENGINEERING, vol. 142, no. 3.View/Download from: Publisher's site
Ren, L, Qu, X, Guan, H, Easa, S & Oh, E 2016, 'Evaluation of Roundabout Capacity Models: An Empirical Case Study', JOURNAL OF TRANSPORTATION ENGINEERING, vol. 142, no. 12.View/Download from: Publisher's site
© 2016 Pan Li and Xiaobo Qu. This paper addresses the issue of optimally selecting the tunnel safety provisions. Tunnel safety provisions are the assets of urban road tunnels which are installed and implemented to reduce the tunnel risks, which are basically selected by expert judgment in practice. An optimization model is proposed to obtain the optimal solution for the selection of tunnel safety provisions. The objective function is to minimize the life cycle costs of tunnel safety provisions, which is subject to the requirements for tunnel safety provisions and the safety targets. Finally, by taking advantage of the special structure of the optimization model, a Bi-Section Search and Bound Algorithm (BSSBA) is designed to efficiently solve the problem.
Wang, S, Liu, Z & Qu, X 2016, 'Minimax Regret Model for Liner Shipping Fleet Deployment with Uncertain Demand', TRANSPORTATION RESEARCH RECORD, no. 2549, pp. 45-53.View/Download from: UTS OPUS or Publisher's site
Kuang, Y, Qu, X, Weng, J & Etemad-Shahidi, A 2015, 'How Does the Driver's Perception Reaction Time Affect the Performances of Crash Surrogate Measures?', PLOS ONE, vol. 10, no. 9.View/Download from: UTS OPUS or Publisher's site
Qu, X & Wang, S 2015, 'Long-Distance-Commuter (LDC) Lane: A New Concept for Freeway Traffic Management', COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, vol. 30, no. 10, pp. 815-823.View/Download from: UTS OPUS or Publisher's site
Qu, X, Jin, S & Weng, J 2015, 'Analysis of the relationship between aggregated traffic volume and traffic conflicts on expressways', Transportmetrica A: Transport Science, vol. 11, no. 7, pp. 648-658.View/Download from: UTS OPUS or Publisher's site
© 2015 Hong Kong Society for Transportation Studies Limited. Numerous efforts have been made to examine the relationship between aggregated traffic volume and conflicts and some inconsistent findings (linear vs. non-linear) have been observed. In this study, we explore the causes of this inconsistency. It is found that traffic conflicts are very similar for all uncongested traffic states, which supports the proportional linear assumptions in many research. By contrast, the conflicts for congested traffic states are significantly higher, which results in a non-linear feature for combined traffic states.
Jin, S, Qu, X, Xu, C, Ma, D & Wang, D 2015, 'An improved multi-value cellular automata model for heterogeneous bicycle traffic flow', PHYSICS LETTERS A, vol. 379, no. 39, pp. 2409-2416.View/Download from: UTS OPUS or Publisher's site
Wang, S & Qu, X 2015, 'Rural bus route design problem: Model development and case studies', KSCE Journal of Civil Engineering, vol. 19, no. 6, pp. 1892-1896.View/Download from: UTS OPUS or Publisher's site
© 2015, Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg. Rural and suburban areas have a low density of population. The bus services for these areas have unique features such as no transfer exists as there is only one bus route for each area and nearly all passengers travel to the same destination of city center. These features make the design of suburban bus route a practical and interesting research topic. We formulate such a suburban bus route design problem as an optimization model. We subsequently prove that the problem is NP-hard. In view of the problem structure, a dynamic programming approach is developed to obtain the optimal solution efficiently for practical-size problems. The optimal solution contains information on which one of the two bus stops on both sides of a street to visit and the sequence of visiting the chosen bus stops. Two case studies based on a square-block example and a suburb in Australia are carried out to demonstrate the applicability of the proposed model and method.
Weng, J, Qiao, W, Qu, X & Yan, X 2015, 'Cluster-based lognormal distribution model for accident duration', TRANSPORTMETRICA A-TRANSPORT SCIENCE, vol. 11, no. 4, pp. 345-363.View/Download from: UTS OPUS or Publisher's site
Weng, J, Zheng, Y, Qu, X & Yan, X 2015, 'Development of a maximum likelihood regression tree-based model for Predicting subway incident delay', TRANSPORTATION RESEARCH PART C-EMERGING TECHNOLOGIES, vol. 57, pp. 30-41.View/Download from: UTS OPUS or Publisher's site
Wang, S, Qu, X & Yang, Y 2015, 'Estimation of the perceived value of transit time for containerized cargoes', TRANSPORTATION RESEARCH PART A-POLICY AND PRACTICE, vol. 78, pp. 298-308.View/Download from: UTS OPUS or Publisher's site
Jin, S, Qu, X, Zhou, D, Xu, C, Ma, D & Wang, D 2015, 'Estimating cycleway capacity and bicycle equivalent unit for electric bicycles', TRANSPORTATION RESEARCH PART A-POLICY AND PRACTICE, vol. 77, pp. 225-248.View/Download from: UTS OPUS or Publisher's site
Weng, J, Xue, S, Yang, Y, Yan, X & Qu, X 2015, 'In-depth analysis of drivers' merging behavior and rear-end crash risks in work zone merging areas', ACCIDENT ANALYSIS AND PREVENTION, vol. 77, pp. 51-61.View/Download from: UTS OPUS or Publisher's site
Qu, X, Wang, S & Zhang, J 2015, 'On the fundamental diagram for freeway traffic: A novel calibration approach for single-regime models', TRANSPORTATION RESEARCH PART B-METHODOLOGICAL, vol. 73, pp. 91-102.View/Download from: UTS OPUS or Publisher's site
Da Costa, S, Qu, X & Parajuli, PM 2015, 'A Crash Severity-Based Black Spot Identification Model', JOURNAL OF TRANSPORTATION SAFETY & SECURITY, vol. 7, no. 3, pp. 268-277.View/Download from: UTS OPUS or Publisher's site
Qu, X, Ren, L, Wang, S & Oh, E 2014, 'Estimation of Entry Capacity for Single-Lane Modern Roundabouts: Case Study in Queensland, Australia', JOURNAL OF TRANSPORTATION ENGINEERING, vol. 140, no. 7.View/Download from: UTS OPUS or Publisher's site
Kuang, Y, Qu, X & Wang, S 2014, 'Propagation and dissipation of crash risk on saturated freeways', TRANSPORTMETRICA B-TRANSPORT DYNAMICS, vol. 2, no. 3, pp. 203-214.View/Download from: UTS OPUS or Publisher's site
Wang, S, Wang, T, Qu, X, Liu, Z & Jin, S 2014, 'Liner Ship Fleet Deployment with Uncertain Demand', TRANSPORTATION RESEARCH RECORD, no. 2409, pp. 49-53.View/Download from: UTS OPUS or Publisher's site
Qu, X, Oh, E, Weng, J & Jin, S 2014, 'Bus travel time reliability analysis: a case study', PROCEEDINGS OF THE INSTITUTION OF CIVIL ENGINEERS-TRANSPORT, vol. 167, no. 3, pp. 178-184.View/Download from: UTS OPUS or Publisher's site
Qu, X, Yang, Y, Liu, Z, Jin, S & Weng, J 2014, 'Potential crash risks of expressway on-ramps and off-ramps: A case study in Beijing, China', SAFETY SCIENCE, vol. 70, pp. 58-62.View/Download from: UTS OPUS or Publisher's site
Qu, X, Kuang, Y, Oh, E & Jin, S 2014, 'Safety Evaluation for Expressways: A Comparative Study for Macroscopic and Microscopic Indicators', TRAFFIC INJURY PREVENTION, vol. 15, no. 1, pp. 89-93.View/Download from: UTS OPUS or Publisher's site
Qu, X, Zhang, J, Wang, S & Liu, Z 2014, 'Modelling follow up time at a single-lane roundabout', Journal of Traffic and Transportation Engineering (English Edition), vol. 1, no. 2, pp. 97-102.View/Download from: UTS OPUS or Publisher's site
© 2014 Periodical Offices of Chang'an University The follow up time is an important parameter for estimating the entry capacity of roundabouts. However, its variability and contributing factors have long been ignored in the literatures. In this study, 171 follow up samples and contributing factors (traffic volume, vehicle position, waiting vehicles behind, vehicle type, and drivers' gender) are collected at a roundabout in Pacific Pines, Australia. It is found that the follow up time is indeed significantly affected by traffic volume, waiting vehicles behind, vehicle type, and drivers' gender. In order to establish the relationship between the follow up time and its contributing factors, an inverse Gaussian regression model is further developed. This relationship could be applied to estimate the entry capacities by taking into account the variability of follow up samples. According to the model, the traffic volume and vehicle types are the most important contributing factors.
Bie, Y, Wang, D & Qu, X 2013, 'Modelling correlation degree between two adjacent signalised intersections for dynamic subarea partition', IET Intelligent Transport Systems, vol. 7, no. 1, pp. 28-35.View/Download from: UTS OPUS or Publisher's site
Correlation degree between adjacent signalised intersections is considered as the most important component in subarea partition algorithm. In this study, contributing factors for subarea partition are selected by taking into consideration the differences with respect to cycle lengths, link length and path flow between upstream and downstream coordinated phases. Their impacts on performance index of subarea partition are further studied using numerical experiments. The study then proceeds to propose a correlation degree index (CI) as an alternative for the performance index in order to reduce the computational complexity. The relationship between CI and the contributing factors is established to predict the correlation degree. Finally, the model is validated using field survey data. © The Institution of Engineering and Technology 2013.
Meng, Q & Qu, X 2013, 'Bus dwell time estimation at bus bays: A probabilistic approach', TRANSPORTATION RESEARCH PART C-EMERGING TECHNOLOGIES, vol. 36, pp. 61-71.View/Download from: UTS OPUS or Publisher's site
Liu, Z, Yan, Y, Qu, X & Zhang, Y 2013, 'Bus stop-skipping scheme with random travel time', TRANSPORTATION RESEARCH PART C-EMERGING TECHNOLOGIES, vol. 35, pp. 46-56.View/Download from: UTS OPUS or Publisher's site
Jin, S, Qu, X, Xu, C & Wang, D-H 2013, 'Dynamic characteristics of traffic flow with consideration of pedestrians' road-crossing behavior', PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS, vol. 392, no. 18, pp. 3881-3890.View/Download from: UTS OPUS or Publisher's site
Qu, X, Meng, Q & Liu, Z 2013, 'Estimation of number of fatalities caused by toxic gases due to fire in road tunnels', ACCIDENT ANALYSIS AND PREVENTION, vol. 50, pp. 616-621.View/Download from: UTS OPUS or Publisher's site
Meng, Q & Qu, X 2012, 'Uncertainty propagation in quantitative risk assessment modeling for fire in road tunnels', IEEE Transactions on Systems, Man and Cybernetics Part C: Applications and Reviews, vol. 42, no. 6, pp. 1454-1464.View/Download from: UTS OPUS or Publisher's site
Road tunnels are critical transportation infrastructures that provide underground passageways for motorists and commuters. Fire in road tunnels in combination with tunnel safety provisions failure may lead to catastrophic consequences, and thus, necessitates a robust and reliable approach to assess tunnel risks. This article proposes a quantitative risk assessment model for fire in road tunnel by taking into consideration two types of uncertainties. A Monte Carlo-based estimation method is developed to propagate parameter uncertainty in quantitative risk assessment model consisting of event tree analysis as well as consequence estimation models. The percentile-based individual risks and α-cut-based societal risks are put up and the risk indices are proven to be very useful for tunnel operators with distinct risk attitudes to assess the safety level of a road tunnel. Finally, the proposed research methodology is applied to Singapore KPE road tunnels. © 1998-2012 IEEE.
Qu, X & Meng, Q 2012, 'Development and applications of a simulation model for vessels in the Singapore Straits', Expert Systems with Applications, vol. 39, no. 9, pp. 8430-8438.View/Download from: UTS OPUS or Publisher's site
The traffic volume in the Singapore Strait will be significantly increased according to the prediction by the United Nations Conference on Trade and Development. Therefore, it is important for the maritime authorities (e.g. Maritime and Port Authority of Singapore) to capture a picture of ship movements in the Straits in the near future. This paper proposed a novel simulation model for ship movements in the narrow and busy shipping channel. The simulation approach is on the basis of a modified Cellular Automata model and takes interactions between consecutive ships into consideration by expert judgment from experienced personnel. Discrete event models are applied to generate vessels with different categories and velocities from four portals of the Strait. Ten ship following rules and five ship crossing rules are used to simulate the mariners' response to various navigational scenarios. The model is further verified by comparing the actual travel time through the Strait and the time derived from the model. At last, applications of the model are illustrated. © 2012 Elsevier Ltd. All rights reserved.
Qu, X & Meng, Q 2012, 'The economic importance of the Straits of Malacca and Singapore: An extreme-scenario analysis', TRANSPORTATION RESEARCH PART E-LOGISTICS AND TRANSPORTATION REVIEW, vol. 48, no. 1, pp. 258-265.View/Download from: UTS OPUS or Publisher's site
Jin, S, Qu, X & Wang, D 2011, 'Assessment of Expressway Traffic Safety Using Gaussian Mixture Model based on Time to Collision', International Journal of Computational Intelligence Systems, vol. 4, no. 6, pp. 1122-1130.View/Download from: UTS OPUS or Publisher's site
Traffic safety is of great significance, especially in urban expressway where traffic volume is large and traffic conflicts are highlighted. It is thus important to develop a methodology that is able to assess traffic safety. In this paper, we first analyze the time to collision (TTC) samples from traffic videos collected from Beijing expressway with different locations, lanes, and traffic conditions. Accordingly, some basic descriptive statistics of 5 locations' TTC samples are shown, and it is concluded that Gaussian mixture model (GMM) distribution is the best-fitted distribution to TTC samples based on K-S goodness of fit tests. Using GMM distribution, TTC samples can be divided into three categories: dangerous situations, relative safe situations, and absolute safe situations, respectively. We then proceeds to introduce a novel concept of the percentage of serious traffic conflicts as the percentage of TTC samples below a predetermined threshold value in dangerous situation. After that, assessment results of expressway traffic safety are presented using the proposed traffic safety indictor. The results imply that traffic safety on the weaving segment is lower than that on mainlines and the percentage of serious traffic conflicts on median lane is larger than that on middle lane and shoulder lane. © 2011 Copyright Taylor and Francis Group, LLC.
Meng, Q, Qu, X, Wang, X, Yuanita, V & Wong, SC 2011, 'Quantitative Risk Assessment Modeling for Nonhomogeneous Urban Road Tunnels', RISK ANALYSIS, vol. 31, no. 3, pp. 382-403.View/Download from: UTS OPUS or Publisher's site
Meng, Q, Qu, X, Yong, KT & Wong, YH 2011, 'QRA Model-Based Risk Impact Analysis of Traffic Flow in Urban Road Tunnels', RISK ANALYSIS, vol. 31, no. 12, pp. 1872-1882.View/Download from: UTS OPUS or Publisher's site
Meng, Q & Qu, X 2011, 'A probabilistic quantitative risk assessment model for fire in road tunnels with parameter uncertainty', International Journal of Reliability and Safety, vol. 5, no. 3-4, pp. 285-298.View/Download from: UTS OPUS or Publisher's site
Fire in road tunnels can lead to catastrophic consequences in combination with tunnel safety provision failures, thus necessitating a need for a reliable and robust approach to assess tunnel risks caused by fire. In a quantitative risk assessment (QRA) model for road tunnels, uncertainty is an unavoidable component because input parameters of the model possess different levels of uncertainties which are inappropriate to be formulated by crisp numbers. In this paper, a Monte Carlo sampling-based QRA model is proposed to address parameter uncertainty of a QRA model. The tunnel risks are assessed in terms of percentile-based societal risk as well as expected number of fatalities (ENF) curve, which would facilitate tunnel managers to make decisions. A case study is carried out to demonstrate the approach. © 2011 Inderscience Enterprises Ltd.
Qu, X, Meng, Q, Yuanita, V & Wong, YH 2011, 'Design and implementation of a quantitative risk assessment software tool for Singapore road tunnels', Expert Systems with Applications, vol. 38, no. 11, pp. 13827-13834.View/Download from: UTS OPUS or Publisher's site
This paper presents an interesting approach to develop a quantitative risk assessment (QRA) software tool for road tunnels. It first introduces a QRA model for road tunnels, consisting of event trees, fault trees and consequence estimation models. The model is developed by taking into account the unique characteristics of Singapore road tunnels. The paper proceeds to describe design of the QRA software tool based on the QRA model by means of the object oriented design (OOD) method and eXtensible Markup Language (XML) technique. The XML files are used to store the numerous tree structures in the proposed model thus making the programming much more efficiently and effectively. The QRA software tool is robust and flexible such that users can easily add or modify the event trees, fault trees and the consequence estimation models. An application to Singapore road tunnels has been carried out to assess the robustness and effectiveness of the QRA software tool. © 2011 Elsevier Ltd. All rights reserved.
Qu, X, Meng, Q & Suyi, L 2011, 'Ship collision risk assessment for the Singapore Strait.', Accident Analysis and Prevention, vol. 43, no. 6, pp. 2030-2036.View/Download from: UTS OPUS or Publisher's site
The Singapore Strait is considered as the bottleneck and chokepoint of the shipping routes connecting the Indian and the Pacific Ocean. Therefore, the ship collision risk assessment is of significant importance for ships passing through the narrow, shallow, and busy waterway. In this paper, three ship collision risk indices are initially proposed to quantitatively assess the ship collision risks in the Strait: index of speed dispersion, degree of acceleration and deceleration, and number of fuzzy ship domain overlaps. These three risk indices for the Singapore Strait are estimated by using the real-time ship locations and sailing speeds provide by Lloyd's MIU automatic identification system (AIS). Based on estimation of these three risk indices, it can be concluded that Legs 4W, 5W, 11E, and 12E are the most risky legs in the Strait. Therefore, the ship collision risk reduction solutions should be prioritized being implemented in these four legs. This study also finds that around 25% of the vessels sail with a speed in excess of the speed limit, which results in higher potentials of ship collision. Analysis indicates that the safety level would be significantly improved if all the vessels follow the passage guidelines.
Kuang, Y & Qu, X 2015, 'Safety Fundamental Diagram on Freeways', CICTP 2015 - Efficient, Safe, and Green Multimodal Transportation - Proceedings of the 15th COTA International Conference of Transportation Professionals, COTA International Conference of Transportation Professionals (CICTP), CICTP, China, pp. 3143-3154.View/Download from: UTS OPUS or Publisher's site
With the increasing losses to society, traffic safety has become essential task to traffic engineers and researchers. In order to visually investigate the relationship between safety and flow condition without the historical crash data, we developed the Safety Fundamental Diagram (SFD) by using the surrogate radar diagram to demonstrate the risk level in a fundamental diagram. We first propose a surrogate radar diagram to describe the risk level by using five well recognised surrogate indicators. Furthermore, the traffic of the Pacific Motorway is simulated with the traffic data provided by the Queensland Department of Transport and Main Roads. By analyzing the different shapes generated in the surrogate radar diagrams, the safety levels of different regimes can be represented in a fundamental diagram visually. This methodology on SFD can also be applied to evaluate the safety impact of different proposed projects proactively before implementation.
Jin, S, Wang, D & Qu, X 2008, 'Maximum likelihood method of speed estimation from single loop outputs', Proceedings of the 8th International Conference of Chinese Logistics and Transportation Professionals - Logistics: The Emerging Frontiers of Transportation and Development in China, pp. 4160-4166.View/Download from: Publisher's site
The importance of real-time speed estimation is undoubtedly significant for traveler information and traffic management systems. Unfortunately, the most common form of traffic detector, the single loop detector, is incapable of providing speed measurements. This paper presents a new method of speed estimation from single loop detector data by using the Maximum Likelihood Method (MLM). On the assumption that a vehicle's velocity obeys lognormal distribution in every sample, the average speed of each sample was estimated using MLM. The algorithm of the proposed method is implemented and evaluated using the field data from urban expressways in Beijing. The results show that the proposed method has more excellent estimation accuracy than the conventional method. © ASCE.