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Transportation planning and management, Urban planning, Traffic engineering, Environment
As international trade and freight volumes increase, there is a growing port congestion problem, leading to the long truck queues at US marine terminal gates. To address this problem, some countermeasures have been proposed and implemented for reducing truck queue length at marine terminals. To assess the effectiveness of these countermeasures, a method for accurately estimating terminal gate truck queue length is needed. This study developed a new method, named the state-dependent approximation method, for estimating the truck queue length at marine terminals. Based on the simulation of the truck queuing system, it was found that it takes several hours for the truck queue length to reach its steady state, and neglecting the queue formation (queue dispersion) processes will cause overestimation (underestimation) of truck queue length. The developed model can take into account the queue formation and dispersion processes, and it can be used to estimate the truck queue length caused by short-term oversaturation at marine terminals. For model evaluation, a simulation-based case study was conducted to evaluate the prediction accuracy of the developed model by comparing its results with the simulated queue lengths and the results of other four existing methods, including the fluid flow model, the M/M/S queuing model, and a simulation-based regression model developed a previous study. The evaluation results indicate that the developed model outperformed the other four modeling methods for different states of queue formation and dispersion processes. In addition, this new method can accurately estimate the truck queue length caused by the short-term system oversaturation during peak hours. Therefore, it will be useful for assessing the effectiveness of the countermeasures that are targeted at reducing the peak-hour congestion at marine terminals.
Wenrui Qu; Tao Tao; Bo Xie; Yi Qi. A State-Dependent Approximation Method for Estimating Truck Queue Length at Marine Terminals. Sustainability 2021, 13, 2917 .
AMA StyleWenrui Qu, Tao Tao, Bo Xie, Yi Qi. A State-Dependent Approximation Method for Estimating Truck Queue Length at Marine Terminals. Sustainability. 2021; 13 (5):2917.
Chicago/Turabian StyleWenrui Qu; Tao Tao; Bo Xie; Yi Qi. 2021. "A State-Dependent Approximation Method for Estimating Truck Queue Length at Marine Terminals." Sustainability 13, no. 5: 2917.
Displaced left-turn (DLT) intersections are designed to increase the mobility of vehicles by relocating the left-turn lane (lanes) to the far-left side of the road upstream of the main signalized intersection. Since DLT is a relatively new design and very limited crash data are available, previous studies have focused mainly on the analysis of its operational performance rather than its safety performance. To fill this gap, in this study, we investigated the safety performance of two DLT intersections located in San Marcos, Texas. Crash data from 2011 to April 2018 were extracted from the TxDOT Crash Record Information System (CRIS). These crash data were analyzed using two different approaches, i.e., statistical analysis and collision diagram-based analysis. The results of this study indicated that DLT did not increase the overall crash frequencies at the studied intersections. Traffic crashes related to left turns and right turns were reduced significantly by DLT. Meanwhile, it also caused safety issues related to traffic signage, traffic signal, geometric design, and access management at DLT intersections. Thus, in the implementation of DLT intersections, traffic engineers need to carefully consider different aspects of the DLT intersection design, including access management, traffic signal coordination, and driver acceptance. As a result of these analyses, recommendations were provided for the safe implementation of the DLT design in the future.
Wenrui Qu; Qiao Sun; Qun Zhao; Tao Tao; Yi Qi. Statistical Analysis of Safety Performance of Displaced Left-Turn Intersections: Case Studies in San Marcos, Texas. International Journal of Environmental Research and Public Health 2020, 17, 6446 .
AMA StyleWenrui Qu, Qiao Sun, Qun Zhao, Tao Tao, Yi Qi. Statistical Analysis of Safety Performance of Displaced Left-Turn Intersections: Case Studies in San Marcos, Texas. International Journal of Environmental Research and Public Health. 2020; 17 (18):6446.
Chicago/Turabian StyleWenrui Qu; Qiao Sun; Qun Zhao; Tao Tao; Yi Qi. 2020. "Statistical Analysis of Safety Performance of Displaced Left-Turn Intersections: Case Studies in San Marcos, Texas." International Journal of Environmental Research and Public Health 17, no. 18: 6446.
Due to their size and weight, trucks require more space and time to make left turns when exiting or entering a roadway. Therefore, appropriate median treatments are critical for roadways with substantial truck traffic. The two-way left-turn lane (TWLTL) and raised median (RM) are the two types of median most commonly used to improve roadway mobility and manage roadway accessibility. However, previous studies on these median treatments have focused primarily on the general traffic conditions and geometric roadway features without considering the truck traffic impact. To fill this gap, this study investigates the truck impacts on TWLTL and RM by considering two major influencing factors – truck percentage and roadway access point density. First, a negative binomial regression is developed to analyze the relationship between crash frequency and various influencing factors. Next, the crash rate difference analysis between the TWLTL and RM is conducted to identify critical points for these two factors. The findings indicate that, compared with RM, TWLTL has significantly higher crash frequency, especially for roadways with a higher percentage of trucks. This suggests that the percentage of trucks should be taken into consideration when selecting an appropriate type of roadway median.
Wenrui Qu; Tao Tao; Qun Zhao; Qiao Sun; Yi Qi. Two-way left turn lane or raised median? A truck safety based study. Journal of Safety Research 2020, 74, 109 -117.
AMA StyleWenrui Qu, Tao Tao, Qun Zhao, Qiao Sun, Yi Qi. Two-way left turn lane or raised median? A truck safety based study. Journal of Safety Research. 2020; 74 ():109-117.
Chicago/Turabian StyleWenrui Qu; Tao Tao; Qun Zhao; Qiao Sun; Yi Qi. 2020. "Two-way left turn lane or raised median? A truck safety based study." Journal of Safety Research 74, no. : 109-117.