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  • Mobility and traffic research  (5)
  • 1
    Online Resource
    Online Resource
    SAGE Publications ; 2023
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2677, No. 4 ( 2023-04), p. 168-180
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2677, No. 4 ( 2023-04), p. 168-180
    Abstract: The research team has utilized privacy-protected mobile device location data, integrated with COVID-19 case data and census population data, to produce a COVID-19 impact analysis platform that can inform users about the effects of COVID-19 spread and government orders on mobility and social distancing. The platform is being updated daily, to continuously inform decision-makers about the impacts of COVID-19 on their communities, using an interactive analytical tool. The research team has processed anonymized mobile device location data to identify trips and produced a set of variables, including social distancing index, percentage of people staying at home, visits to work and non-work locations, out-of-town trips, and trip distance. The results are aggregated to county and state levels to protect privacy, and scaled to the entire population of each county and state. The research team is making their data and findings, which are updated daily and go back to January 1, 2020, for benchmarking, available to the public to help public officials make informed decisions. This paper presents a summary of the platform and describes the methodology used to process data and produce the platform metrics.
    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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  • 2
    Online Resource
    Online Resource
    SAGE Publications ; 2011
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2255, No. 1 ( 2011-01), p. 58-68
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2255, No. 1 ( 2011-01), p. 58-68
    Abstract: “Accessibility,” defined as the ease (or difficulty) with which opportunities for activity can be reached from a given location, can be measured with the cumulative amount of opportunities from an origin within a given amount of travel time. These indicators can be used in regional planning and modeling efforts to integrate land use and travel demand, and an attempt should be made to calculate these indicators for the smallest geographic area. The primary objective of this paper is to illustrate the creation of realistic space-sensitive and time-sensitive block-level accessibility indicators to track the availability of opportunities. These indicators support the development of an activity-based travel demand model by Southern California Association of Governments to provide second-by-second and parcel-by-parcel modeling and simulation. The indicators also provided the base information for mapping opportunities of access to 15 types of industries at different times during a day. The indicators and their maps were defined for the entire region of Southern California through largely available data that included the Census Transportation Planning Package, Dun & Brad-street postprocessed data, detailed highway networks and travel times from the four-step regional models, and arrival and departure times of workers by industry.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2011
    detail.hit.zdb_id: 2403378-9
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  • 3
    Online Resource
    Online Resource
    SAGE Publications ; 2014
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2448, No. 1 ( 2014-01), p. 28-36
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2448, No. 1 ( 2014-01), p. 28-36
    Abstract: Railways are required to operate with a high level of reliability and safety for transporting passengers. Because the wheel is one of the key subsystems of a railway train, it can contribute significantly to the train's reliability and safety. One important way to meet the requirements is to implement proper maintenance activities. A modeling approach is developed on the basis of Petri nets for the maintenance analysis of wheels. The detailed maintenance and renewal options to be explored for wheel maintenance are discussed. The model is solved with Monte Carlo simulation to investigate the effectiveness of maintenance actions. Moreover, the developed model can be flexible, and different ways in which the complexity of the model can be extended are discussed. A case study is conducted to demonstrate the execution of the model. Analysis of the results shows that the model is useful in predicting life-cycle wheel maintenance activities and costs throughout the train's life, and this information can be used in maintenance optimization.
    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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  • 4
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2676, No. 9 ( 2022-09), p. 407-420
    Abstract: The purpose of this study was to determine the quantitative time conversion relationship between indoor accelerated weathering aging (AWA) and outdoor natural aging of the high-content polymer modified asphalt (HCPMA) applied in porous asphalt pavement from both theoretical and experimental aspects. Firstly, the calculated aging acceleration rate of the AWA test was determined based on orthogonal analysis and chemical reaction kinetics. The indoor AWA test (0–12 days) and outdoor natural aging (0–12 months) were then performed on HCPMA, and the dynamic shear rheology test and multiple stress creep recovery test were conducted to investigate the rheological properties of HCPMA. Furthermore, the measured aging acceleration rate of the AWA test was determined according to rheological index comparison and then compared with the calculated aging acceleration rate to obtain the ultimate time conversion relationship between indoor and outdoor aging. Results show that it is practical to simulate the natural aging by using the AWA test. HCPMA exhibits similar changes in macroscopic rheological properties in indoor AWA and outdoor natural aging. According to the comparison of rheological indexes, the measured aging acceleration rate of HCPMA under the harshest aging condition is 57.5–120, which is basically consistent with the calculated aging acceleration rate (66) by the chemical reaction kinetics. This further demonstrates the feasibility of this study for determining the indoor-outdoor aging time conversion relationship from theoretical and experimental aspects.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2022
    detail.hit.zdb_id: 2403378-9
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  • 5
    Online Resource
    Online Resource
    SAGE Publications ; 2018
    In:  Transportation Research Record: Journal of the Transportation Research Board Vol. 2672, No. 25 ( 2018-12), p. 89-98
    In: Transportation Research Record: Journal of the Transportation Research Board, SAGE Publications, Vol. 2672, No. 25 ( 2018-12), p. 89-98
    Abstract: Eco-driving behavior is able to improve vehicles’ fuel consumption efficiency and minimize exhaust emissions, especially with the presence of infrastructure-to-vehicle (I2V) communications for connected vehicles. Several techniques such as dynamic programming and neural networks have been proposed to study eco-driving behavior. However, most techniques need a complicated problem-solving process and cannot be applied to dynamic traffic conditions. Comparatively, reinforcement learning (RL) presents great potential for self-learning to take actions in a complicated environment to achieve the optimal mapping between traffic conditions and the corresponding optimal control action of a vehicle. In this paper, a vehicle was treated as an agent to select its maneuver, that is, acceleration, cruise speed, and deceleration, according to dynamic conditions while approaching a signalized intersection equipped with I2V communication. An improved cellular automation model was utilized as the simulation platform. Three parameters, including the distance between the vehicle and the intersection, signal status, and instant vehicle speeds, were selected to characterize real-time traffic state. The total CO 2 emitted by the vehicle on the approach to the intersection serves as a measure of reward policy that informs the vehicle how good its operation was. The Q-learning algorithm was utilized to optimize vehicle driving behaviors for eco-driving. Vehicle exhaust emissions and traffic performance (travel time, stop duration, and stop rate) were evaluated in two cases: (1) an isolated intersection, and (2) a medium-scale realistic network. Simulation results showed that the eco-driving behavior obtained by RL can not only reduce emissions but also optimize traffic performance.
    Type of Medium: Online Resource
    ISSN: 0361-1981 , 2169-4052
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2018
    detail.hit.zdb_id: 2403378-9
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