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  • Mobility and traffic research  (20)
  • 1
    Online Resource
    Online Resource
    Modeling of Passing Events in Mixed Bicycle Traffic with Cellular Automata
    SAGE Publications ; 2013
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2387, No. 1 ( 2013-01), p. 26-34
    Details
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2387, No. 1 ( 2013-01), p. 26-34
    Abstract: The primary objective of this study was to use the cellular automata (CA) method to model the characteristics of bicycle passing events in mixed bicycle traffic on separated bicycle paths. The mixed traffic was composed of two types of bicycles: the conventional bicycle (c-bicycle) and the electric bicycle (e-bicycle). The number of passing events and the characteristics of mixed bicycle traffic were investigated in the field on eight physically separated bicycle paths in China. Then a CA model was calibrated with the use of the field data to simulate the passing events in the mixed bicycle traffic. The results showed that the CA model could simulate the features of bicycle passing events well. The simulation results were consistent with field observations. An increase in the ratio of e-bicycles would not significantly increase the number of passing events, but e-bicycles did contribute substantially to passing events in mixed bicycle traffic. E-bicycles were shown to have more stability than c-bicycles, especially in traffic with a high flow rate. The findings of this study could improve the performance of simulation techniques to reflect the actual characteristics of mixed bicycle traffic.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    URL: Article
    DOI: 10.3141/2387-04
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2013
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  • 2
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    Optimal Structure Combination for Inverted Asphalt Pavement Incorporating Cracks in Cement-Treated Subbase
    SAGE Publications ; 2020
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2674, No. 1 ( 2020-01), p. 68-78
    Details
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2674, No. 1 ( 2020-01), p. 68-78
    Abstract: The structure design and mechanistic calculation of inverted asphalt pavements are mainly based on linear layer elastic theory with the assumption that the cement-treated subbase (CTB) is complete without cracks. This study investigates the optimal structure combination for inverted pavements according to calculated critical responses considering cracks in the CTB layer. A three-dimensional finite element (3D FE) model of inverted pavement with a transverse crack through the CTB layer was developed. Four full-scale inverted pavement sections were built, and a crack 0.01 m wide and 0.05 m deep was sawn on top of each CTB layer after construction. The 3D FE model was validated by strain and deformation measured in falling weight deflectometer tests and used for a parametric study of dominating structure combination factors. Variance analysis results show that interactions with thickness or stiffness of the asphalt concrete (AC) layer presented the most significant effect on critical responses, while CTB stiffness (12588~7668 MPa) had the least impact. Structure variation effect analysis results illustrated that 0.1 m aggregate base (AB) thickness is enough to prevent the CTB crack propagating to the surface. Thin AC structures are highly sensitive to variations in AC and AB stiffness. A thin AC and AB combination (0.05 and 0.10 m) can provide low critical strains similar to a thick AC and thin AB (0.15 and 0.10 m) combination if the stiffness of AC and AB can be maintained at 7175 and 358 Mpa, respectively, or higher. AC thickness of 0.1 m and the combination of thin AC and thick AB are two unfavorable conditions for inverted pavements.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    URL: Article
    DOI: 10.1177/0361198119899056
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2020
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  • 3
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    Surrogate Evaluation Model for Assessing Lane Detection Reliability of Automated Vehicles in Complex Road Environments
    SAGE Publications ; 2023
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2677, No. 7 ( 2023-07), p. 185-195
    Details
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2677, No. 7 ( 2023-07), p. 185-195
    Abstract: The reliability of environmental perception is the key to ensuring the stability and safety of autonomous vehicles. Complex road environments pose attentional challenges to automated driving, especially for vehicle perception systems. Therefore, evaluating the performance of autonomous driving algorithms in complex road environments is of great significance. However, as road geometry is complex, with many factors, including curvature, slope, lane marking conditions, and so on, the existing approach in assessing an algorithm through detection tests is of low efficiency. Therefore, this study relies on failure prediction modeled by extreme gradient boosting and recursive feature elimination. An evaluation model that could accomplish a quick set of road evaluations is developed. The proposed model generates recognition reliability merely by such features as road design parameters. In addition, road curvature is the most significant environmental factor affecting the perception of autonomous vehicles. The failure rates of the algorithm in different scenarios demonstrate a negative correlation between the radius of curvature and failure perception. The partial dependence involving the radius of curvature and the perception ability is obtained. Furthermore, other features, such as missing lane lines and illumination conditions, are taken into consideration to explore the potential failure perception mode. The proposed method has a particular significance for finding the failure mode of an autonomous driving perception algorithm.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    URL: Article
    DOI: 10.1177/03611981231152260
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2023
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  • 4
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    Convolutional Neural Network with Attention Module for Identification of Tunnel Seepage
    SAGE Publications ; 2022
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2676, No. 11 ( 2022-11), p. 112-123
    Details
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2676, No. 11 ( 2022-11), p. 112-123
    Abstract: As tunnel construction proceeds ever more rapidly, the efficiency of seepage detection by engineers with expert knowledge is facing unprecedented challenges. Moreover, it suffers from strong subjectivity. In recent years, deep learning, as an algorithm of machine learning, has achieved state-of-the-art performance in pattern recognition. In this paper, we address such a problem by building convolutional neural networks that operate on conventional graphics processing units. Within the project, the data is obtained by an infrared thermal imager since there exist different characteristics of temperature between the area of seepage and non-seepage. Considering the difficulty of collecting many images, generative adversarial nets and other data augmentation skills are applicable to enlarge data sets. We design several novel architectures where the attention mechanism is plugged into various traditional models, considered as VGG16 network with Attention Module and RestNet34 with Attention Module, and the overall identification accuracy achieved is more than 97%. The codes of this project can be found at https://github.com/Scotter-Qian/cnn .
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    URL: Article
    DOI: 10.1177/03611981221091774
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2022
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  • 5
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    Online Resource
    Traffic Safety Assessment with Integrated Communication System of Connected and Automated Vehicles at Signalized Intersections
    SAGE Publications ; 2023
    In:  Transportation Research Record: Journal of the Transportation Research Board
    Details
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications
    Abstract: Connected and automated vehicles (CAVs) are expected to improve traffic safety effectively at signalized intersections. Considerable studies have been conducted to investigate the benefits of CAVs in improving traffic mobility and efficiency. However, in most previous research, vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication have been considered separately rather than concurrently, to study the characteristics of CAVs, resulting in the potential of CAVs not being fully exploited and inconsistency with reality. In this paper, an integrated communication system of CAVs (ICSC), which incorporates V2V and V2I communication, is proposed, to assess traffic safety at signalized intersections. In this study, the intelligent driver model (IDM) is used to approximate V2V communication between a subject CAV and preceding CAVs. A reinforcement learning algorithm is adopted to model V2I communication between a CAV and a traffic light. The traffic safety effect of ICSC, V2V-only, and V2I-only scenarios is evaluated for different market penetration rates (MPRs). The results show that the ICSC scenario significantly reduces traffic conflicts and outperforms V2V-only, V2I-only, and benchmark scenarios when the MPR is equal to or higher than 50% with different surrogate safety measures (SSMs), such as time-exposed deceleration (TED) to avoid crashing, time exposed time-to-collision (TET), and use of a spacing gap (SGAP). Moreover, the mobility effect of the ICSC scenario is studied, and appears to increase average speed and reduce delay time. Finally, the results suggest that the ICSC can improve traffic safety and mobility concurrently and exploit the potentials of CAVs at signalized intersections.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    URL: Article
    DOI: 10.1177/03611981231201107
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2023
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  • 6
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    Spatial Analysis of Maritime Accidents Using the Geographic Information System
    SAGE Publications ; 2013
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2326, No. 1 ( 2013-01), p. 39-44
    Details
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2326, No. 1 ( 2013-01), p. 39-44
    Abstract: Despite the tremendous efforts of maritime organizations to achieve a safe and secure maritime transportation system, the losses through maritime accidents and incidents are still increasing. This paper analyzes the spatial distribution of maritime accidents occurring from January 1, 2002, to December 31, 2011, based on the Marine Casualties and Incidents module of the Global Integrated Shipping Information System. The geographic information system, an effective and efficient tool for spatial analysis with high visualization, is used to carry out the analysis. Hot-spot analysis of maritime accidents identifies the hot spots. Buffer analysis is used to calculate accidents that occurred in coastal areas. Finally, the following two important results are obtained from the analysis. First, the identification of hot spots reveals the area around the United Kingdom as the area with the greatest number of accidents and the coastal areas around East Asian countries (such as China, Japan, and South Korea) and the Mediterranean Sea as the areas with the next highest number of accidents. These results compare well with a previously published paper. Second, maritime accidents may not frequently occur in the open sea; however, accidents frequently happen in coastal areas, with 51.1% of the total accidents happening within 25 mi of the continents and 62.2% within 50 mi.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    URL: Article
    DOI: 10.3141/2326-06
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2013
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  • 7
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    Online Resource
    Generalized Sign Recognition Based on the Gaussian Statistical Color Model for Intelligent Road Sign Inventory
    SAGE Publications ; 2016
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2596, No. 1 ( 2016-01), p. 28-35
    Details
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2596, No. 1 ( 2016-01), p. 28-35
    Abstract: The rapid progress in sensor and information technologies makes it possible to develop intelligent road sign inventory (IRSI) by automatically collecting and processing vehicle-borne multisensor data. This study developed a framework for IRSI with a vehicle-borne multisensor system. The IRSI framework consists of four modules: ( a) sensor vehicle design for multisensor data collection, ( b) sign recognition, ( c) sign data integration and attribute computation, and ( d) IRSI-based applications. Within the framework, sign recognition is the key to IRSI. The study proposed a novel Gaussian statistical color model (G-SCM) for image segmentation and color feature extraction. The G-SCM has good capability to model actual sign color distributions and has fast implementation for G-SCM-based color segmentation. With color features integrated into sign texture, shape, location, and other features, a novel generalized recognition algorithm is proposed for sign inventory. The proposed G-SCM model and the sign recognition method were tested with actual video log images. The experimental results show that the G-SCM can model actual sign colors and segment sign images accurately. The fast implementation can greatly enhance computation speed compared with existing color analysis methods. The developed sign recognition algorithm was tested to recognize all speed limit signs from video log images collected along a 140-km highway segment. The algorithm recognized 30 of 31 signs and achieved a 96.8% site recognition rate. Of the 136 images containing speed limit signs, the algorithm had only eight false positives. The results demonstrate that the proposed sign recognition method is promising for the development of IRSI.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    URL: Article
    DOI: 10.3141/2596-04
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2016
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  • 8
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    Study on Service-Level Classification of Platforms in Beijing Urban Rail Transit
    SAGE Publications ; 2009
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2112, No. 1 ( 2009-01), p. 127-135
    Details
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2112, No. 1 ( 2009-01), p. 127-135
    Abstract: The classification standards of levels of service (LOSs) for urban rail transit platforms are the foundation of platform design and evaluation. To study platform LOSs in urban rail transit, the passenger perception method and stated preference investigation concept were adopted, and a questionnaire was designed to investigate the factors influencing LOSs. The survey results showed that the congestion level of the platform was the most important factor influencing the LOS of the platform, followed by passenger order, air quality, information signs, and waiting time. On the basis of the results of the survey, the congestion level was used as the basis for the development of a LOS standard for platforms. A stated preference questionnaire was designed to investigate platform LOSs by using photos showing different congestion levels. According to the survey results, the membership curve of different LOSs was drawn, and the perceived LOS of the platform was classified into five levels on the basis of the congestion level. With linear interpolation, critical values of pedestrian density corresponding to different LOSs were calculated. Finally, the LOS standards developed for transit platforms were compared with the LOS criteria for pedestrian queuing areas offered by the Highway Capacity Manual, and possible reasons for the differences were analyzed. The proposed LOS standards for urban rail transit platforms can be used as a reference for transit design and evaluation.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    URL: Article
    DOI: 10.3141/2112-16
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2009
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  • 9
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    Capacities of Unsignalized Intersections under Mixed Vehicular and Nonmotorized Traffic Conditions
    SAGE Publications ; 2009
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2130, No. 1 ( 2009-01), p. 129-137
    Details
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2130, No. 1 ( 2009-01), p. 129-137
    Abstract: Unsignalized intersections consist of three types–-two-way stop-controlled, all-way stop-controlled, and uncontrolled intersections–- all with different priority relationships between traffic movements according to traffic laws. A conflict technique method was used to develop capacity models for the three types of unsignalized intersections under mixed traffic conditions involving vehicular, bicycle, and pedestrian movements. With field data collected from several unsignalized intersections, the model parameters were calibrated by a comparison analysis of traffic conditions in China and were modified on the basis of actual traffic conditions. The capacities obtained by the proposed models matched well with the observed capacities and the capacities calculated by conventional methods, both of which verified the effectiveness of the proposed models. The models proved to be valuable tools for determining capacities of vehicular movements at unsignalized intersections.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    URL: Article
    DOI: 10.3141/2130-16
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2009
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  • 10
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    Cybersecurity Attacks in Vehicle-to-Infrastructure Applications and Their Prevention
    SAGE Publications ; 2018
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2672, No. 19 ( 2018-12), p. 66-78
    Details
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2672, No. 19 ( 2018-12), p. 66-78
    Abstract: A connected vehicle (CV) environment is comprised of diverse computing infrastructure, data communication and dissemination, and data collection systems that are vulnerable to the same cyberattacks as all traditional computing environments. Cyberattacks can jeopardize the expected safety, mobility, energy, and environmental benefits from CV applications. As cyberattacks can lead to severe consequences such as traffic incidents, it has become one of the primary concerns in CV applications. In this paper, we evaluate the impact of cyberattacks on the vehicle-to-infrastructure (V2I) network from a V2I application point of view. Then, we develop a novel V2I cybersecurity architecture, named CVGuard, which can detect and prevent cyberattacks on the V2I applications. In designing CVGuard, key challenges, such as scalability, resiliency and future usability were considered. A case study using a distributed denial of service (DDoS) attack on a V2I application, “Stop Sign Gap Assist (SSGA)” application, shows that CVGuard was effective in mitigating the adverse safety effects created by a DDoS attack. In our case study, because of the DDoS attack, conflicts between the minor and major road vehicles occurred at an unsignalized intersection, which could have caused crashes. A reduction of conflicts between vehicles occurred because CVGuard was in operation. The reduction of conflicts was compared based on the number of conflicts before and after the implementation and operation of the CVGuard security platform. Analysis revealed that the strategies adopted by CVGuard were successful in reducing the conflicts by 60% where a DDoS attack compromised the SSGA application at an unsignalized intersection.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    URL: Article
    DOI: 10.1177/0361198118799012
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2018
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