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  • Mobility and traffic research  (3)
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  • Mobility and traffic research  (3)
  • 1
    Online Resource
    Online Resource
    SAGE Publications ; 2014
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2443, No. 1 ( 2014-01), p. 21-31
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2443, No. 1 ( 2014-01), p. 21-31
    Abstract: Traffic flow prediction is considered a key technology of intelligent transportation systems. This paper presents a hybrid model that combines double exponential smoothing (DES) and a support vector machine (SVM) to predict traffic flow patterns on the basis of weekly similarities in traffic flow. First, in the hybrid model, DES is applied to predict the future data, and its smoothing parameters are determined by the Levenberg–Marquardt algorithm. Second, the SVM is employed to estimate the residual series between the prediction results by the DES model and actual measured data. In the SVM model, the cross-correlation rule is used to optimize its parameters. Third, a case study to test the proposed model with the data at different temporal scales is presented. Furthermore, data-smoothing strategies, including difference and ratio schemes based on weekly similarities, are applied as data processes before prediction. The proposed hybrid model along with the processing scheme demonstrates superiority in prediction accuracy compared with autoregressive integrated moving average, DES, and DES-SVM models.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2014
    detail.hit.zdb_id: 2403378-9
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  • 2
    Online Resource
    Online Resource
    SAGE Publications ; 2015
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2528, No. 1 ( 2015-01), p. 86-95
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2528, No. 1 ( 2015-01), p. 86-95
    Abstract: The lack of some traffic flow data seriously affects the quality of data collection and analysis in the traffic system. Completing the missing data is one of the most important steps in achieving the functions of intelligent transportation systems. In this paper an approach based on fuzzy C-means (FCM) imputes missing traffic volume data in loop detectors. With spatial–temporal correlation between detectors, the conventional vector-based data structure is first transformed into a matrix-based data pattern. Then, the genetic algorithm is applied to optimize the parameters of cluster size and weighting factor in the FCM model. Finally, the actual traffic flow volume collected at different locations is designed as a testing data set, and two indicators including root mean square error and relative accuracy are used to evaluate the imputation performance of the proposed method by comparison with some conventional methods (multiple linear regression, autoregressive integrated moving average model, and average historical method) by missing ratio. The applications in four scenarios demonstrate that the FCM-based imputation method outperforms conventional methods.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2015
    detail.hit.zdb_id: 2403378-9
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  • 3
    Online Resource
    Online Resource
    SAGE Publications ; 2023
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2677, No. 5 ( 2023-05), p. 1030-1045
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2677, No. 5 ( 2023-05), p. 1030-1045
    Abstract: With the widespread application of unmanned aerial vehicles (UAVs), flight safety issues have gradually become prominent. To improve the safety level of UAV flight, a conceptual model was constructed through groups of unsafe behaviors of UAV flight based on the Swiss cheese model (reason model). The relationship network model of unsafe behaviors of UAV flight was built after using the two-mode and one-mode social network analysis, and the unsafe behaviors of UAV flight influence mechanism were studied by basic characteristics of network analysis, centrality analysis, core-periphery structure analysis, in/out-degree analysis, and structural hole analysis. The results showed that the two-mode network is closely related: unreasonable safety management structure of the organization and weak supervision of UAV flight operation were those unsafe behaviors of UAV supervision that had great influence. The unsafe behaviors of UAV supervision, such as the organization’s illegal deployment of unqualified personnel for tasks and lack of ground commander for the mission plan, were in the core position of the network. The proposed model can effectively reduce the unsafe behaviors of UAV operations by eliminating critical unsafe behaviors of UAV supervision in the network and reducing UAV flight accidents.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2023
    detail.hit.zdb_id: 2403378-9
    Location Call Number Limitation Availability
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