Many bridge design specifications consider multi-lane factors(MLFs)a critical component of the traffic load model.Measured multi-lane traffic data generally exhibit significant lane disparities in traffic loads over m...Many bridge design specifications consider multi-lane factors(MLFs)a critical component of the traffic load model.Measured multi-lane traffic data generally exhibit significant lane disparities in traffic loads over multiple lanes.However,these disparities are not considered in current specifications.To address this drawback,a multi-coefficient MLF model was developed based on an improved probabilistic statistical approach that considers the presence of multiple trucks.The proposed MLF model and approach were calibrated and demonstrated through an example site.The model sensitivity analysis demonstrated the significant influence of lane disparity of truck traffic volume and truck weight distribution on the MLF.Using the proposed approach,the experimental site study yielded MLFs comparable with those directly calculated using traffic load effects.The exclusion of overloaded trucks caused the proposed approach,existing design specifications,and conventional approach of ignoring lane load disparity to generate comparable MLFs,while the MLFs based on the proposed approach were the most comprehensive.The inclusion of overloaded trucks caused the conventional approach and design specifications to overestimate the MLFs significantly.Finally,the benefits of the research results to bridge practitioners were discussed.展开更多
The on-ramp merging in multi-lane highway scenarios presents challenges due to the complexity of coordinating vehicles’merging and lane-changing behaviors,while ensuring safety and optimizing traffic flow.However,the...The on-ramp merging in multi-lane highway scenarios presents challenges due to the complexity of coordinating vehicles’merging and lane-changing behaviors,while ensuring safety and optimizing traffic flow.However,there are few studies that have addressed the merging problem of ramp vehicles and the cooperative lane-change problem of mainline vehicles within a unified framework and proposed corresponding optimization strategies.To tackle this issue,this study adopts a cyber-physical integration perspective and proposes a graph-based solution approach.First,the information of vehicle groups in the physical plane is mapped to the cyber plane,and a dynamic conflict graph is introduced in the cyber space to describe the conflict relationships among vehicle groups.Subsequently,graph decomposition and search strategies are employed to obtain the optimal solution,including the set of mainline vehicles changing lanes,passing sequences for each route,and corresponding trajectories.Finally,the proposed dynamic conflict graph-based algorithm is validated through simulations in continuous traffic with various densities,and its performance is compared with the default algorithm in SUMO.The results demonstrate the effectiveness of the proposed approach in improving vehicle safety and traffic efficiency,particularly in high traffic density scenarios,providing valuable insights for future research in multi-lane merging strategies.展开更多
Existing studies on modern roundabouts performance are mostly based on data fron： singe lane roundabouts that are not heavily congested. For planners and designers interested in building multilane roundabouts for int...Existing studies on modern roundabouts performance are mostly based on data fron： singe lane roundabouts that are not heavily congested. For planners and designers interested in building multilane roundabouts for intersections with potential growth i~ future traffic, there has been a lack of existing studies with field data that provide reference values in terms of capacity and delay measurements. With the intent of providing such reference values, a case study was conducted by using the East DowlinC Road Roundabouts in Anchorage, Alaska, which are currently operating with extensive queues during the evening peak hours. This research used multiple video camcorders t（ capture vehicle turning movements at the roundabouts as well as the progressior~ of vehicle queues at the roundabout entrance approaches. With these video records, the number of vehicles in the queues can be accurately counted in any single minute during the peak hours. This study shows that unbalanced entrance flow patterns （i.e., ~ne entrance has significant higher flow than others） can intensify the queue and delay fo., the overall roundabouts. Then various software packages including RODEL, SIDRA and VISSIM were used to estimate several performance measurements, such as capacity. queue length, and delay, compared with the collected field data. With the comparison, it is found that all the three software packages overestimate multi-lane roundabout ca pacity before calibration. With default parameters, SIDRA and VISSIM tend to underes timate delays and queue lengths for the multi-lane roundabouts under congestion, while RODEL results in higher delay and queue length estimations at most of the entrance approaches.展开更多
为缓解逆向可变车道交叉口左转流压力导致的通行效率低、运行不稳定及能耗问题,本文考虑不同自动化水平下自动驾驶车辆(Autonomous Vehicle,AV)与网联自动驾驶车辆(Connected and Autonomous Vehicle,CAV)的混行趋势,构建一种可变车道...为缓解逆向可变车道交叉口左转流压力导致的通行效率低、运行不稳定及能耗问题,本文考虑不同自动化水平下自动驾驶车辆(Autonomous Vehicle,AV)与网联自动驾驶车辆(Connected and Autonomous Vehicle,CAV)的混行趋势,构建一种可变车道背景下左转车辆的轨迹控制方法。在控制时域内建立以通行效率最大化与能耗最小化为目标的多目标轨迹优化模型,引入AV与CAV在信息感知和协同能力上的差异,实现动态调控车队加减速和变道行为,并采用分支定界算法求解变道信息与行驶轨迹。进一步设计持续型、集中型与均衡型3类典型交通情境,结合不同CAV渗透率进行数值模拟分析。结果表明:轨迹优化控制模型能够有效改善车队的纵向时空分布,降低停车次数与队列波动;在持续型、集中型与均衡型情境下,分别在CAV渗透率为20%、50%与100%时效果最佳,相较于能耗优先与效率优先方法,持续型场景综合指标分别下降约51.5%与38.9%,集中型分别下降16.2%与40.8%,均衡型情境分别下降10.7%与33.2%;同时,轨迹控制模型在车头时距与可变车道长度变化下表现出较强的鲁棒性。展开更多
基金This work was supported by the National Natural Science Foundation of China(Grant No.51808148)Natural Science Foundation of Guangdong Province,China(No.2019A1515010701)Guangzhou Municipal Science and Technology Project(No.201904010188).
文摘Many bridge design specifications consider multi-lane factors(MLFs)a critical component of the traffic load model.Measured multi-lane traffic data generally exhibit significant lane disparities in traffic loads over multiple lanes.However,these disparities are not considered in current specifications.To address this drawback,a multi-coefficient MLF model was developed based on an improved probabilistic statistical approach that considers the presence of multiple trucks.The proposed MLF model and approach were calibrated and demonstrated through an example site.The model sensitivity analysis demonstrated the significant influence of lane disparity of truck traffic volume and truck weight distribution on the MLF.Using the proposed approach,the experimental site study yielded MLFs comparable with those directly calculated using traffic load effects.The exclusion of overloaded trucks caused the proposed approach,existing design specifications,and conventional approach of ignoring lane load disparity to generate comparable MLFs,while the MLFs based on the proposed approach were the most comprehensive.The inclusion of overloaded trucks caused the conventional approach and design specifications to overestimate the MLFs significantly.Finally,the benefits of the research results to bridge practitioners were discussed.
基金supported by the National Key R&D Program of China(2022YFB2503200)the National Natural Science Foundation of China,Science Fund for Creative Research Groups(52221005).
文摘The on-ramp merging in multi-lane highway scenarios presents challenges due to the complexity of coordinating vehicles’merging and lane-changing behaviors,while ensuring safety and optimizing traffic flow.However,there are few studies that have addressed the merging problem of ramp vehicles and the cooperative lane-change problem of mainline vehicles within a unified framework and proposed corresponding optimization strategies.To tackle this issue,this study adopts a cyber-physical integration perspective and proposes a graph-based solution approach.First,the information of vehicle groups in the physical plane is mapped to the cyber plane,and a dynamic conflict graph is introduced in the cyber space to describe the conflict relationships among vehicle groups.Subsequently,graph decomposition and search strategies are employed to obtain the optimal solution,including the set of mainline vehicles changing lanes,passing sequences for each route,and corresponding trajectories.Finally,the proposed dynamic conflict graph-based algorithm is validated through simulations in continuous traffic with various densities,and its performance is compared with the default algorithm in SUMO.The results demonstrate the effectiveness of the proposed approach in improving vehicle safety and traffic efficiency,particularly in high traffic density scenarios,providing valuable insights for future research in multi-lane merging strategies.
基金sponsored by Alaska University Transportation Center(AUTC,No.RR08.08)Alaska Department of Transportation(AK DOT)
文摘Existing studies on modern roundabouts performance are mostly based on data fron： singe lane roundabouts that are not heavily congested. For planners and designers interested in building multilane roundabouts for intersections with potential growth i~ future traffic, there has been a lack of existing studies with field data that provide reference values in terms of capacity and delay measurements. With the intent of providing such reference values, a case study was conducted by using the East DowlinC Road Roundabouts in Anchorage, Alaska, which are currently operating with extensive queues during the evening peak hours. This research used multiple video camcorders t（ capture vehicle turning movements at the roundabouts as well as the progressior~ of vehicle queues at the roundabout entrance approaches. With these video records, the number of vehicles in the queues can be accurately counted in any single minute during the peak hours. This study shows that unbalanced entrance flow patterns （i.e., ~ne entrance has significant higher flow than others） can intensify the queue and delay fo., the overall roundabouts. Then various software packages including RODEL, SIDRA and VISSIM were used to estimate several performance measurements, such as capacity. queue length, and delay, compared with the collected field data. With the comparison, it is found that all the three software packages overestimate multi-lane roundabout ca pacity before calibration. With default parameters, SIDRA and VISSIM tend to underes timate delays and queue lengths for the multi-lane roundabouts under congestion, while RODEL results in higher delay and queue length estimations at most of the entrance approaches.
文摘为缓解逆向可变车道交叉口左转流压力导致的通行效率低、运行不稳定及能耗问题,本文考虑不同自动化水平下自动驾驶车辆(Autonomous Vehicle,AV)与网联自动驾驶车辆(Connected and Autonomous Vehicle,CAV)的混行趋势,构建一种可变车道背景下左转车辆的轨迹控制方法。在控制时域内建立以通行效率最大化与能耗最小化为目标的多目标轨迹优化模型,引入AV与CAV在信息感知和协同能力上的差异,实现动态调控车队加减速和变道行为,并采用分支定界算法求解变道信息与行驶轨迹。进一步设计持续型、集中型与均衡型3类典型交通情境,结合不同CAV渗透率进行数值模拟分析。结果表明:轨迹优化控制模型能够有效改善车队的纵向时空分布,降低停车次数与队列波动;在持续型、集中型与均衡型情境下,分别在CAV渗透率为20%、50%与100%时效果最佳,相较于能耗优先与效率优先方法,持续型场景综合指标分别下降约51.5%与38.9%,集中型分别下降16.2%与40.8%,均衡型情境分别下降10.7%与33.2%;同时,轨迹控制模型在车头时距与可变车道长度变化下表现出较强的鲁棒性。
