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  • Mobility and traffic research  (18)
  • 11
    Online Resource
    Online Resource
    SAGE Publications ; 2021
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2675, No. 4 ( 2021-04), p. 181-200
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2675, No. 4 ( 2021-04), p. 181-200
    Abstract: The matching of crowdsourced drivers and delivery tasks is an important decision problem for the crowdsourced delivery platform. Although the existence of uncertainty of transportation duration in logistics delivery has been verified, uncertain transportation duration has not been considered in previous studies on the matching of crowdsourced drivers and delivery tasks. This would lead to the limitation that the results of the existing methods cannot meet the time requirements of senders. In this case, the profit and customer satisfaction of the crowdsourced delivery platform would decrease. In this paper, a model-based rolling matching strategy to match crowdsourced drivers and delivery tasks considering uncertain transportation duration is proposed. In addition, it is assumed that the crowdsourced delivery platform also has some dedicated drivers to implement the delivery tasks that cannot be implemented by crowdsourced drivers. First, a simpler problem is described, which is to match crowdsourced drivers and delivery tasks considering uncertain transportation duration in a static data environment. Then, a model is proposed to solve the above problem. Based on the proposed model, this paper further proposes a rolling procedure to solve the problem in a data refreshing environment. Moreover, a heuristic algorithm is presented for combining multiple delivery tasks to solve the one-to-many matching. Finally, a case study and comparison are given to illustrate the validity and the contribution of the proposed matching strategy. The results show that the proposed matching strategy has a distinct advantage of cost savings.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2021
    detail.hit.zdb_id: 2403378-9
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  • 12
    Online Resource
    Online Resource
    SAGE Publications ; 2023
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2677, No. 1 ( 2023-01), p. 1311-1326
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2677, No. 1 ( 2023-01), p. 1311-1326
    Abstract: As a new form of shared mobility similar to bike-sharing, there is an increasing trend of people starting to use shared electric bicycles (SEB) for travel in China. Understanding the psychosocial factors that affect residents’ intention to use SEB is essential for the implementation of policies to develop sustainable transportation. Most research focuses on bike-sharing, while research on SEB is relatively rare. As such, this study proposes a theoretical framework based on the Theory of Planned Behavior (TPB) and the Technology Acceptance Model (TAM) to explore the mechanisms that influence the acceptance of and intention to use SEB. Drawing on this, it further addresses the moderating role of group heterogeneity and the residual effect of bike-sharing. An online survey of 313 SEB users in China was conducted in 2021. The results are constructed by structural equation modeling (SEM) and multiple-indicator multiple-cause (MIMIC) model. The results show that the research model can well explain people’s intention to use SEB. Perceived usefulness, attitude, subjective norm, and perceived behavioral control have direct positive effects on the intention to use SEB. However, there is group heterogeneity between social-economic attributes and latent variables. Moreover, satisfaction with bike-sharing could moderate the relationship between perceived usefulness and intention toward SEB. Based on the findings, some policy insights from users, government, and enterprises are proposed to guide the development of SEB.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2023
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  • 13
    Online Resource
    Online Resource
    SAGE Publications ; 2017
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2631, No. 1 ( 2017-01), p. 20-29
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2631, No. 1 ( 2017-01), p. 20-29
    Abstract: Rutting and cracking occur simultaneously in asphalt mixtures as observed in the field and in the laboratory. Existing mechanical models have not properly addressed viscoelastic and viscoplastic deformation together with cracking attributable to model deficiencies, parameter calibration, and numerical inefficiency. This study developed viscoelasticplastic–fracture (VEPF) models for the characterization of viscoelasticity by Prony model and viscoplasticity by Perzyna’s flow rule with a generalized Drucker–Prager yield surface and a nonassociated plastic potential. Viscofracture damage was modeled by a viscoelastic Griffith criterion and a pseudo J-integral Paris’s law for crack initiation and propagation, respectively. The VEPF models were implemented in a finite element program by using a weak form partial differential equation modeling technique without the need for programming user-defined material subroutines. Model parameters were derived from fundamental material properties by using dynamic modulus, strength, and repeated load tests. Simulations indicated that the viscoelastic–viscoplastic–viscofracture characteristics were effectively modeled by the VEPF models for asphalt mixtures at different confinements and temperatures. An asphalt mixture under monotonic compressive loads exhibited a sequenced process including a pure viscoelastic deformation stage, a coupled viscoelastic–viscoplastic deformation stage, a viscoelastic–viscoplastic deformation coupled with a viscofracture initiation and a propagation stage, and then a viscoelastic–viscofracture rupture stage with saturated viscoplastic deformation. The asphalt mixture under repeated loads yielded an increasing viscoplastic strain at an increasing rate during the first half of the haversine load, while the increment of the viscoplastic strain (per load cycle) decreased with load cycles. The finite element program, which is based on a partial differential equation, effectively modeled the coupled viscoelastic–viscoplastic–viscofracture behaviors of the asphalt mixtures.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2017
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  • 14
    Online Resource
    Online Resource
    SAGE Publications ; 2009
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2124, No. 1 ( 2009-01), p. 222-230
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2124, No. 1 ( 2009-01), p. 222-230
    Abstract: The distribution of time headway has long been a research topic because headway between vehicles is an important flow characteristic affecting safety, level of service, driver behavior, and capacity of a transportation system. However, almost all reported research on headway is focused on mixed vehicular flow without considering the difference in headway with respect to different vehicle types. In this paper, with the use of 1-day freeway traffic data from Interstate 35 in Austin, Texas, four time headway types based on different combinations of leading vehicles and following vehicles–-car–truck, truck–car, truck–truck, and car–car–-are analyzed at different traffic flow levels. Statistical comparisons between each vehicle type–specific headway and mixed vehicle–type headway are made to verify their significant differences. The paper demonstrates the necessity of vehicle type–specific headway study. The results of the paper not only identify qualitative differences between the vehicle type–specific headways and distributions, but also can be used as a reference for practical applications, especially for improving microscopic traffic simulation models.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2009
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  • 15
    Online Resource
    Online Resource
    SAGE Publications ; 2023
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2677, No. 3 ( 2023-03), p. 1340-1356
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2677, No. 3 ( 2023-03), p. 1340-1356
    Abstract: Dynamic traffic assignment (DTA) methods have been developed fruitfully in theory but are limited in application. Reasons may include the high computational complexity, the difficulty in model calibration, and the reliance on accurate and complete origin–destination (OD) data. Recognizing the incompleteness of OD data in the real world, this paper proposes a deep learning-based DTA model. Specifically, a convolution neural network (CNN) is chosen to account for the spatial correlation of OD pairs. The CNN-based DTA model is trained with the input of historical OD data (incomplete because of limited survey tools) and the output of link flow data (complete thanks to detection technologies). These data are obtained first by simulations in experimental networks and then from an empirical survey in Dazhou, China. Extensive experiments are done about various levels of data incompleteness (measured by the percentage of missing OD data). Comparisons show that the trained CNN-based DTA model performs better with higher accuracy than other common statistical/machine learning algorithms (e.g., feed-forward neural network, k-nearest neighbor, and Kriging). The proposed model also shows robustness to the small-sized dataset, data noise, and network changes. Additional examinations include employing the proposed framework to learn and estimate traffic flow characteristics (i.e., average speed and travel time) and the dynamic flow of turning movements at intersections. Lastly, a case study demonstrates the application of the proposed model using real data. Overall, this study indicates the promising prospect of the CNN-based DTA model as a supplement to traditional ones.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2023
    detail.hit.zdb_id: 2403378-9
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  • 16
    Online Resource
    Online Resource
    SAGE Publications ; 2019
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2673, No. 11 ( 2019-11), p. 296-308
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2673, No. 11 ( 2019-11), p. 296-308
    Abstract: It is of interest to federal and state agencies to develop an advanced uniform method for estimation of vehicle miles traveled (VMT) on local roads which can be used as a guideline for agencies nationwide. The purpose of this study is to propose advanced innovative approaches for estimating VMT on local roads and analyze the feasibility of applying these methods. The paper presents a methodology and procedure for estimating local road VMT using GPS vehicle trajectory data and an all-street road network and expands these methodologies and results to determine the minimum required GPS sample size. The Federal Highway Administration and other transportation agencies may consider using these methodologies as a future guide to update VMT estimates with minimal additional cost requirements. The key finding of the research is that it is feasible to use new GPS vehicle trajectory data to estimate VMT on non-Federal Aid System roadways. The sample size of this data allows the application of this new method across the nation. The accuracy of this method was tested for the State of Maryland. Once such statewide GPS data is obtained by a given state, the methodology can be easily applied to that state as well.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2019
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  • 17
    Online Resource
    Online Resource
    SAGE Publications ; 2019
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2673, No. 11 ( 2019-11), p. 791-800
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2673, No. 11 ( 2019-11), p. 791-800
    Abstract: Because of limited access to global positioning system (GPS) signals, accurate and reliable localization for intelligent vehicles in underground parking lots is still an open problem. This paper proposes a multi-view and multi-scale localization method aiming at solving this problem. The proposed method is divided into an offline mapping stage and an online localization stage. In the mapping stage, the offline map is generated by fusing 3-D information, WiFi features, visual features, and trajectory from visual odometry (VO). In the localization stage, WiFi fingerprint matching is exploited for coarse localization. Based on the result of coarse localization, multi-view localization is exploited for image-level localization. Finally, metric localization is exploited to refine the localization results. By applying this multi-scale strategy, it is possible to fuse WiFi localization and visual localization and reduce the image matching and error rate to a great extent. Because of exploiting more information, multi-view localization is more robust and accurate than single-view localization. The method is tested in a 2,000 m 2 underground parking lot. The result demonstrates that this method can achieve sub-meter localization on average. The proposed localization method can be a supplement to the existing intelligent vehicle localization techniques.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2019
    detail.hit.zdb_id: 2403378-9
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  • 18
    Online Resource
    Online Resource
    SAGE Publications ; 2016
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2580, No. 1 ( 2016-01), p. 34-46
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2580, No. 1 ( 2016-01), p. 34-46
    Abstract: This study evaluated the benefits of geogrid reinforcement on unbound granular materials (UGMs) in terms of cross-anisotropy and stress-dependent permanent deformation by using repeated-load triaxial (RLT) tests. One type of crushed granite material and three types of geogrid were selected for the RLT tests. The influence of the aperture type, the sheet stiffness, and the location of the geogrid was quantified in terms of the increase of resilient modulus and the reduction of permanent deformation of the UGMs. The RLT test results indicated that the geogrid reinforced both the vertical and horizontal resilient moduli of the UGM but did not affect its anisotropic ratio. The geogrid with triangular apertures and high sheet stiffness placed in the middle of a UGM specimen provided the most benefits in reinforcing the cross-anisotropic resilient modulus and reducing the permanent deformation. To characterize the stress-dependent permanent deformation of geogrid-reinforced UGMs, a mechanistic–empirical rutting model was proposed by incorporating a softening stress term and a hardening stress term into the Tseng–Lytton model. A new permanent deformation test protocol was developed to determine the model coefficients and to examine the model’s prediction accuracy. The comparison of the model-predicted permanent strain curves with those measured in laboratory tests confirmed that the developed rutting model accurately captured the stress dependences of the permanent deformation for the geogrid-reinforced UGM. The determined rutting model coefficients can be used to predict the permanent deformation of UGMs at any stress level and number of load repetitions.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2016
    detail.hit.zdb_id: 2403378-9
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