Operational Evaluation of U-Turns at At-Grade Signalized Diamond Interchanges

Zhou, Hongmin; Tydlacka, Jonathan; Ding, Liang

doi:10.1177/0361198119840341

Cited by 2 publications

(2 citation statements)

References 9 publications

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“…Five of them were on IH 45 North southbound (SB), and one was on IH 610 North westbound (WB) in Houston, Texas, U.S. All six sites are single lane ramps as with all other ramp meters in Houston. The five ramps on IH 45 are associated with an X-ramp configuration, that is, an entrance (exit) ramp exists immediately upstream (downstream) of an intersection on the same side of the freeway (12). The popular X-ramp pattern in Texas often creates a situation where an exit ramp exists immediately upstream of the entrance ramp.…”

Section: Study Sites and Study Planmentioning

confidence: 99%

Results from Phase I of a Pilot Study on Dynamic Ramp Metering in Houston

Zhou

Kozman

2020

Transportation Research Record

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Traffic in Houston, U.S., has continued growing over the past decade. The Houston District of the Texas Department of Transportation (TxDOT) recently began a pilot study to evaluate a dynamic ramp metering system. The project is aimed to convert ramp metering from local control to system-wide dynamic operation. In Phase I of the project, major control parameters and different metering strategies were tested and evaluated in simulation and field settings for a study corridor installed with six ramp meters. The study identified a base metering plan that overall worked well for sites without restrictive queue conditions. This base plan was that average speed of 50 mph or lower in the right-most two mainlanes will call for metering at a constant metering rate of 850 vehicles per hour for at least 4 min, and that queue occupancy of 50% or higher will call for meter shutdown for at least 1 min. Ramp metering coordinated with the downstream intersection performed well by accommodating diverted traffic caused by ramp metering. When operating ramp meters in a group, metering the immediately upstream meter performed best compared with metering further upstream meters. It is evident that ramp metering caused traffic diversion to the frontage road and also caused reduced queue-jumping behaviors on the frontage road at ramp meters with an immediately upstream exit ramp. The coordinated ramp metering strategy can potentially generate a benefit/cost ratio of 117:1 compared with local metering in the District.

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Section: Study Sites and Study Planmentioning

confidence: 99%

Results from Phase I of a Pilot Study on Dynamic Ramp Metering in Houston

Zhou

Kozman

2020

Transportation Research Record

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“…Furthermore, U-turns in medians are also widely applied to freeway interchanges [16][17][18]. Scholars have conducted analyses from the perspective of safety sight distances to understand their impact on safety [19,20].…”

Section: Introductionmentioning

confidence: 99%

The Impact of Parallel U-Turns on Urban Intersection: Evidence from Chinese Cities

Shi,

Tian,

et al. 2023

Sustainability

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As the number of motor vehicles in China’s cities continues to increase, the imbalance between the capacity that existing urban roads have for construction and the demand for motor vehicles is becoming increasingly evident. Indeed, the design of the intersection U-turn scheme has garnered significant attention from researchers. However, as the number of vehicles requiring U-turns increases, the traditional U-turn in the median or U-turn at the intersection fails to meet the timely demand for U-turns. In such cases, vehicles needing to make U-turns are required to queue first. As the queue length grows, it ultimately impacts the operational efficiency of the intersection. To optimize the imbalance between supply and demand at these intersections and promote the sustainable development of intersections, an innovative form of U-turn organization called the Parallel U-turn has been developed. In the engineering practice of reconstructing existing intersections or constructing new ones, it is crucial to investigate the compatibility between various U-turn design forms and traffic volumes. This exploration helps ensure that the chosen U-turn design effectively accommodates the specific traffic demands at the intersection. Therefore, in this paper, a typical intersection in Xi’an was chosen as the study intersection to investigate traffic data. The researchers calibrated and simulated four U-turn organization schemes using VISSIM microsimulation software. The four schemes included a traditional U-turn at the intersection, a Parallel U-turn at the intersection, a traditional U-turn in the median, and a Parallel U-turn in the median. Then, the researchers used the entropy-weighted TOPSIS method (EWTM) to evaluate the compatibility of each U-turn organization scheme for different traffic combinations. This assessment was conducted based on three criteria: operational efficiency, environmental protection, and safety performance. The results of this study indicate that the Parallel U-turn design is advantageous for the XiaoZhai intersection in Xi’an, China, under specific traffic conditions. When the traffic volume at the intersection exceeds 5940 vehicles per hour but remains below the intersection’s maximum capacity, implementing the Parallel U-turn design could yield positive outcomes in terms of operational efficiency, safety performance, and a reduction in intersection pollution. In summary, by enhancing operational efficiency, safety, and environmental impact, the Parallel U-turn design promotes the overall performance and sustainability of the XiaoZhai intersection and the transportation system in Xi’an, China.

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Operational Evaluation of U-Turns at At-Grade Signalized Diamond Interchanges

Cited by 2 publications

References 9 publications

Results from Phase I of a Pilot Study on Dynamic Ramp Metering in Houston

Results from Phase I of a Pilot Study on Dynamic Ramp Metering in Houston

The Impact of Parallel U-Turns on Urban Intersection: Evidence from Chinese Cities

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