Effect of Geometry and Control on the Probability of Breakdown and Capacity at Freeway Merges

Asgharzadeh, Mohamadamin; Kondyli, Alexandra

doi:10.1061/jtepbs.0000381

Cited by 8 publications

(5 citation statements)

References 24 publications

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“…Further comparison between the optimum volumes and the conventional capacity values indicated that the optimum volume is a reasonable estimator of freeway design capacity. This was also supported by other researchers (16)(17)(18).…”

Section: Literature Reviewsupporting

confidence: 86%

Optimum Volume of Freeway Corridors

Shojaat

Geistefeldt

Wolshon

2020

Transportation Research Record: Journal of the Transportation R

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Conventional methods to assess the quality of service on freeways are based on the comparison of a specific peak hour traffic demand to the capacity of the facility, which is usually measured at a single uniform bottleneck section. However, estimating the quality of service of one bottleneck section may not be sufficient to assess the performance of an entire freeway facility. A driver traveling along a freeway corridor may actually encounter multiple flow breakdowns at independent bottleneck sections, which affect the overall quality of service. This paper introduces a comprehensive approach that considers an entire freeway corridor as a system consisting of successive independent bottlenecks with different characteristics, and can be used to estimate the optimum sustainable volume. The methodology is based on the sustained flow index, which is defined as the product of traffic volume and the probability of survival at this volume. Optimum volumes of two real-world corridors are estimated based on the new derivations. The empirical results reveal that the optimum volume and the capacity of an entire corridor is less than those of its most restrictive bottleneck.

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Section: Literature Reviewsupporting

confidence: 86%

Optimum Volume of Freeway Corridors

Shojaat

Geistefeldt

Wolshon

2020

Transportation Research Record: Journal of the Transportation R

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“…However, the omission or shortening of auxiliary lanes does not appear to significantly affect operational efficiency in certain conditions [32]. The detrimental impact of overflow traffic from ramps on the capacity in merging areas has also been established, suggesting a correlation between the number of lanes and capacity bottlenecks [33], [34]. These studies provide important references and inspiration for the design of three-lane ramps.…”

Section: Introductionmentioning

confidence: 80%

Evaluation of Sustainable Design Method for Three-Lane Entrance Ramps on Expressways in Urban Areas: A Case Study of Xi’an, China

Liu,

Pan,

Song

et al. 2023

IEEE Access

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Owing to the challenges faced by two-lane entrance ramps in merging areas on expressways in handling the growing traffic volume, designers are considering implementing three-lane entrance ramps. This approach alleviates capacity bottlenecks and facilitates efficient, safe, and green operations. However, according to the traditional design strategy, the long auxiliary lanes will bring large land occupation and construction consumption, creating obstacles to the reconstruction. To address this issue, this study proposes two new strategies and discusses the applicability of each scheme. A VISSIM microsimulation model was developed and calibrated using the collected data, and five evaluation indicators assessing environmental protection, capacity, traffic efficiency, safety, and construction consumption were selected. This study also presents a comprehensive evaluation(CE) method that combines the CRITIC (Criteria Importance Through Intercriteria Correlation) method and TOPSIS(Technique for Order Preference by Similarity to an Ideal Solution), which considers the association between indicators and offers a more rational evaluation, aiming to recommend optimal designs for various traffic cases. The results indicate that two-lane ramps are still the preferred choice for lower traffic volumes and merging ratios, whereas three-lane ramps demonstrate excellent potential for application under heavy traffic conditions. The CE reveals substantial improvements in optimal designs, with capacity, delay, CO emissions, and conflicts showing maximum enhancements of approximately 20%, 45%, 5%, and 55%, respectively.

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“…The analysis of the speed data shows that the speed drop initially occurs at the downstream RTMS (#410) compared with upstream RTMS (#409). This speed drop order shows that the upstream demand is not high enough to generate a bottleneck effect even though the number of lanes drops from three to two; consequently, the upstream flow considered as two lanes, because merging flow is compromise of two lanes [16]. As the total number of merging lanes at upstream and on-ramp flows are four and at the downstream three, this lane combination leads to define the FM1 as one lane drop merge.…”

Section: Study Areamentioning

confidence: 99%

“…It is concluded that speed drop is a superior indicator for estimation of breakdown compared to occupancy or volume-occupancy relationship on FMs [15]. Asgharzadeh and Kondyli [16] analyzed breakdown probability flow rates with considering number of lanes, ramp flow rate, presence of lane drops and ramp-metering. They concluded that number of lanes exposed inverse relationship with the average pre-breakdown flow rate per lane.…”

Section: Literature Reviewmentioning

confidence: 99%

Investigation of the Relationship Between Upstream and on-Ramp Flows at Downstream Capacity Level on Istanbul Freeway Merges

Aksoy

Öğüt

2021

Mugla Journal of Science and Technology

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Traffic congestion usually occurs at freeway merges due to the inequality of lane numbers at upstream and downstream. The freeway entry, defined as on-ramp, is the main cause of this irregularity and in order to clarify its effect, three freeway merges are investigated in this study with macroscopic flow parameters where a variety of geometric properties are present. In each merge, when the capacity flow is achieved at downstream, the on-ramp and upstream flows are determined and the relationship between upstream flow rate and 'on-ramp ratio', which is calculated by dividing the on ramp flow rate to the sum of on-ramp and upstream flow rates, is investigated. An inverse relationship is determined between total upstream flows (upstream flow plus on-ramp flow) with respect to on-ramp ratio. As a result, the merge with one lane drop and three-lanes at downstream seems to be least influenced type while the merge with two lanes drop and four lanes at downstream is the highest. For the former, 1% increase in on-ramp ratio causes a reduction of 20 pcu/h/lane on sum of total upstream flows while for the latter 26 pcu/h/lane. It is seen that the term on ramp ratio, can be quite useful variable for establishing capacities of freeway merges with the help of upstream and on-ramp traffic demands.

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Effect of Geometry and Control on the Probability of Breakdown and Capacity at Freeway Merges

Cited by 8 publications

References 24 publications

Optimum Volume of Freeway Corridors

Optimum Volume of Freeway Corridors

Evaluation of Sustainable Design Method for Three-Lane Entrance Ramps on Expressways in Urban Areas: A Case Study of Xi’an, China

Investigation of the Relationship Between Upstream and on-Ramp Flows at Downstream Capacity Level on Istanbul Freeway Merges

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