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排序方式： 共有1103条查询结果，搜索用时 15 毫秒
201.
To mitigate airport congestion caused by increasing air traffic demand, the trajectory‐based surface operations concept has been proposed to improve surface movement efficiency while maintaining safety. It utilizes decision support tools to provide optimized time‐based trajectories for each aircraft and uses automation systems to guide surface movements and monitor their conformance with assigned trajectories. Whether the time‐based trajectories can be effectively followed so that the expected benefits can be guaranteed depends firstly on whether these trajectories are realistic. So, this paper first deals with the modeling biases of the network model typically used for taxi trajectory planning via refined taxiway modeling. Then it presents a zone control‐based dynamic routing and timing algorithm upon the refined taxiway model to find the shortest time taxi route and timings for an aircraft. Finally, the presented algorithm is integrated with a sequential planning framework to continuously decide taxi routes and timings. Experimental results demonstrate that the solution time for an aircraft can be steadily around a few milliseconds with timely cleaning of expired time windows, showing potential for real‐time decision support applications. The results also show the advantages of the proposed methodology over existing approaches. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
202.
Work zones exist widely on urban arterials in the cities that are undergoing road construction or maintenance. However, the existing studies on arterial work zones are very limited, especially on the work zones at urban intersections, although they have a severe negative impact on the urban traffic system. For the first time, this study focuses on how work zones reduce intersection capacity. A type of widely observed work zone, the straddling work zone that straddles on a road segment and an intersection, is studied. A linear regression model and a multiplicative model suggested by Highway Capacity Manual are proposed respectively to determine the saturation flow rate of the signal intersection with the straddling work zone. The data of 22 straddling work zones are collected and used to evaluate the performances of the proposed models. The results display that the linear regression model outperforms the multiplicative model suggested by Highway Capacity Manual. The study also reveals that reducing approach (or exit) lanes and the mixture of motor vehicles and non‐motor vehicles (and pedestrians) can significantly decrease the capacity of the intersection with straddling work zone. Therefore, in setting a straddling work zone, workers should try to ensure that the intersection approach and exit are unobstructed and set a separation for non‐motors and pedestrians to avoid mixed traffic flow. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
203.
Integrated land use and transportation forecasting models are used to assist decision-makers in the policy analysis and infrastructure capital improvement selection process. These models are typically given precise, point-estimate inputs that are mathematically linked, through a series of submodels, to forecasted model outputs. These point-estimate inputs represent an unrealistic level of precision and a growing body of research is focusing on statistical techniques to model uncertainty in model inputs and parameters and tracking the effects of this uncertainty through the various submodels to the model outputs. This paper presents an uncertainty analysis of the Large Zone Economic Module (LZEM) of the Simple, Efficient, Elegant, and Effective Model (SE3M) of land use and transportation. Three case-study implementations of the model are used to obtain a reasonably sound approximation of how uncertainty affects LZEM outputs: Guam, Puerto Rico, and Oahu, Hawaii. These case studies were the subject of an early transferability study with SE3M and were selected based on both their insularity and diverse physical, economic, and demographic geographies. The findings of this research demonstrate that LZEM has a robust framework, with the potential to estimate error both in the positive and negative direction under uncertain input/parameter conditions. 相似文献
204.
Highway work zones caused excessive delay to road users. To reduce user and maintenance costs, work zones shall be designed and scheduled accordingly. An analytical model is developed to jointly optimize work zone lengths and schedule as well as diverted traffic volume for highway maintenance projects, considering time‐varying demand, variable maintenance cost, and various production rates of maintenance crew. With a genetic algorithm, an iterative procedure is developed to search for the optimal solution. A numerical example is illustrated, in which various traffic mitigation plans for a highway maintenance project are evaluated. A sensitivity analysis is conducted, and results indicate the threshold volumes for various conditions (e.g., maintenance crews and capacity of the work zone) at which diverting traffic is desirable. This study demonstrates an effective approach to search for the optimal work zone schedule, which is also applicable to evaluate the effectiveness of traffic diversion plans for a pre‐planned work zone schedule. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
205.
Many accidents occurring at signalized intersections are closely related to drivers’ decisions of running through intersections during yellow light, i.e., yellow-light running (YLR). Therefore it is important to understand the relationships between YLR and the factors which contribute to drivers’ decision of YLR. This requires collecting a large amount of YLR cases. However, existing data collection method, which mainly relies on video cameras, has difficulties to collect a large amount of YLR data. In this research, we propose a method to study drivers’ YLR behaviors using high-resolution event-based data from signal control systems. We used 8 months’ high-resolution data collected by two stop-bar detectors at a signalized intersection located in Minnesota and identified over 30,000 YLR cases. To identify the possible reasons for drivers’ decision of YLR, this research further categorized the YLR cases into four types: “in should-go zone”, “in should-stop zone”, “in dilemma zone”, and “in optional zone” according to the driver’s location when signal turns to yellow. Statistical analysis indicates that the mean values of approaching speed and acceleration rate are significantly different for different types of YLR. We also show that there were about 10% of YLR drivers who cannot run through intersection before traffic light turns to red. Furthermore, based on a strong correlation between hourly traffic volume and number of YLR events, this research developed a regression model that can be used to predict the number of YLR events based on hourly flow rate. This research also showed that snowing weather conditions cause more YLR events. 相似文献
206.
AbstractThis paper aims to clearly establish the origin and evolution of the shared space concept from a New Zealand perspective by reviewing the literature in the disciplines of both urban design and transportation engineering. The review process involves investigating the use and function of a public road space in the context of the changing of public expectations and how this can relate to a number of interconnected street design approaches (e.g. traffic calming and self-explaining roads (SERs)). These approaches have been used to minimise the influence of motor vehicles since the beginning of the automobile era. The shared space concept, when applied in public road environments in activity centres, has increasingly been embraced by urban planners, transportation engineers and regulatory agencies. A shared space diverges from a conventional road where all road users are encouraged to legitimately occupy the same road space with little physical separation. To achieve this in a safe and efficient manner, the design aims to reduce the dominance of the motor vehicle by promoting pedestrian and cycling activity and utilising the road space as a ‘place’ in addition to its ‘transport’ mobility and access purposes. Given the fundamental conceptual differentiation between a traffic-calmed street and a shared space, the paper argues that there are certain design elements, constituting a shared space, and without them, it would be difficult for a public street to function as a genuine shared space for all road users. 相似文献
207.
纤维沥青混合料在多年冻土地区的应用 总被引：3，自引：0，他引：3
通过两种纤维沥青混合料的马歇尔、低温抗裂、冻融劈裂、高温车辙等试验与试验路修筑观测,分析了纤维沥青混合料在多年冻土地区的适用性。研究得出,在相同沥青含量下,纤维沥青混合料的密度明显减小,空隙率和矿料间隙率增大,沥青饱和度、稳定度和流值有所降低。纤维沥青混合料的蠕变速率及其对沥青含量的敏感性减小,弯拉应变增大,柔性明显增强。在相同沥青含量下,纤维沥青混合料的抗冻性有所降低,但实际应用中通过提高最佳沥青用量,可以缓解这种不利的影响。纤维沥青混合料的动稳定度明显增大,对改善沥青混合料的高温稳定性十分有利。纤维沥青混凝土试验路的裂缝间距明显增大,使用状况良好。结果表明,纤维沥青混合料在多年冻土地区有良好的使用价值。 相似文献
208.
以贵州某高速公路一浅埋偏压连拱隧道为背景,从工程实际出发,结合有限元数值模拟探讨挤压带对偏压隧道边坡稳定性的影响及治理措施。分析结果表明,挤压带对边坡稳定性起到主要控制作用。有限元数值模拟结果显示,由于挤压带的存在,边坡顶部沿挤压带下缘处开裂,这与实际观察结果一致;计算结果还表明,在右硐室、强风化带及挤压带交接处,出现剪应力集中,导致局部剪切破坏,边坡可能沿着此条潜在滑动面失稳。针对挤压带力学性能差以及由此引起强风化带开裂、剪切损伤而导致强度下降的情形,提出了抗滑桩与钢花管注浆共同作用的治理方案。地表注浆有利于提高隧道顶板岩体的完整性和强度,对隧洞施工安全及为重要。 相似文献
209.
210.