Increasing Freeway Merge Capacity Through On-ramp Metering PDF Download
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Author: Jittichai Rudjanakanoknad
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 84
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Book Description
Author: Jittichai Rudjanakanoknad
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 84
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Book Description
Author: Michael J. Cassidy
Publisher:
ISBN:
Category : Express highway interchanges
Languages : en
Pages : 24
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Book Description
Observations of two freeway/on-ramp merges unveil the mechanism that causes their capacities to diminish when queues form just upstream. Field experiments at one of the sites demonstrate that by responding to occupancies measured near the merge, ramp metering can reverse this mechanism, or postpone its occurrence, and thereby generate higher merge capacities. Detailed observations at the second site imply that higher merge capacities can also be achieved using traffic control schemes that regulate inflows to the merge from the freeway shoulder lane. Collectively, the findings point to further experiments needed to refine capacity-enhancing control schemes so that such schemes might enjoy wide spread deployment.
Author: Michael James Cassidy
Publisher:
ISBN:
Category : Highway capacity
Languages : en
Pages : 48
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Book Description
Measurements taken downstream of freeway/on-ramp merges have verified that discharge flow diminishes when a merge becomes an active bottleneck. We show that metering the on-ramp can recover the higher discharge flow and thereby increase merge capacity. Detailed observations collected using video revealed that the outflow drop following activation was triggered by a queue that formed near the merge in the freeway shoulder lane and then spread laterally, as drivers changed lanes to maneuver around slow traffic. Once restrictive metering mitigated this shoulder lane queue, high outflows often returned to the median lane. Merge outflow could be increased to levels measured prior to the bottleneck activation by then relaxing the metering rate so that inflows from the on-ramp increased. Although outflows recovered in this fashion were unstable and never persisted for periods greater than 13 mins, the findings are the first real evidence that ramp metering can favorably affect the capacity of an isolated merge. The findings point to control strategies that might stabilize outflow and increase merge capacity even more.
Author: Michael James Cassidy
Publisher:
ISBN:
Category : Express highway interchanges
Languages : en
Pages : 52
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Book Description
This report describes traffic details measured at a freeway merge before and after it became a bottleneck during six observation days. Findings indicate that flows departing this merge can be made substantially higher by metering the on-ramp to restrict the rate its vehicles enter the freeway. It follows then that ramp meters can postpone a bottleneck's activation.
Author: James Robinson
Publisher:
ISBN:
Category : Electronic traffic controls
Languages : en
Pages : 28
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Book Description
Author: Michael DeGaspari
Publisher:
ISBN:
Category :
Languages : en
Pages : 164
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Book Description
Increasing demand on freeway facilities is a major challenge facing urban areas in the United States and throughout the world. Active Traffic Management (ATM) strategies can be used to increase the performance of these facilities through improved operations without the significant expenditure associated with adding capacity. One ATM strategy that has been widely deployed in the current state of practice is ramp metering, which controls the traffic demand placed on a freeway. Merge control strategies are less prevalent and largely undeveloped. This study examines the recurrently congested northbound section of Interstate Highway 35 that approaches downtown Austin, Texas. Using the VISSIM microsimulation platform, a model of this segment was developed and calibrated to reflect current peak-hour congestion. Within this model, ramp metering and merge control technologies were implemented. The impacts on traffic throughput, speed and travel time for each of these proposed systems are evaluated.
Author: Xingan David Kan
Publisher:
ISBN:
Category :
Languages : en
Pages : 105
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Book Description
On-ramp metering at freeway bottlenecks is an effective method of reducing a freeway system's delay because empirical studies have previously shown that metering can prevent capacity drop, or reduction of outflow as a result of queue formation. However, arterial traffic signals that facilitate access to freeway on-ramps operate independent of the traffic conditions on the freeway on-ramp. Consequently, the traffic signals employ long signal cycle lengths and thus long green durations to maximize capacity at the arterial signalized intersections, which result in long platoons of freeway-bound traffic advancing toward the on-ramps. This often causes queue spillback on the freeway on-ramps and the surface street network. Queue override, a function that terminates or significantly relaxes the on-ramp metering rate whenever a sensor placed at the entrance of the on-ramp detects a potential queue spillover of the on-ramp vehicles on the adjacent surface streets, has become a widely accepted method of resolving queue spillback on the freeway on-ramps and nearby surface streets. Unfortunately, queue override releases the queue into the freeway and negates the benefit of ramp metering during the peak hours with recurrent freeway congestion. Video data collected downstream of freeway/on-ramp merge in San Jose, California show that the bottleneck discharge flow diminishes when queue override is activated for a sustained period of time. Observations over a two-week period suggest that queue override reduces the bottleneck discharge flow by an average of 10%. Recently, there has been significant interest in integrated corridor management (ICM) of facilities comprised of freeways and adjacent arterial streets. Significant benefits can be realized by preventing queue override and effectively storing the queued vehicles on the nearby arterial surface streets if the arterial traffic signals can account for traffic conditions on freeway on-ramps and avoid sending long platoons to the freeway on-ramp. A signal control strategy was developed and evaluated in this study. The algorithm takes available on-ramp storage and freeway ramp metering rate into account and dynamically reduces the cycle length and adjusts the green durations to prevent on-ramp queue spillback and mitigate unnecessary delay in the conflicting arterial directions. The proposed algorithm was tested through simulation and the results show that the proposed strategy reduces the freeway and system-wide delay even under fluctuations in traffic demand, at a modest penalty on the on-ramp bound traffic.
Author: Carroll J. Messer
Publisher:
ISBN:
Category : Electronic traffic controls
Languages : en
Pages : 114
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Book Description
Freeway ramp metering systems have been used to improve urban freeway flow. However, control strategies must be properly adjusted to account for ramp queues overflowing onto surface streets and provide equitable on-ramp control during various operating periods. An improved solution can be obtained by optimizing this problem simultaneously for a group of time slices. This study identifies and examines a microcomputer-based optimization scheme that can assist in developing efficient freeway control strategies for on-line freeway surveillance and control. A multi-level freeway control structure is employed for which ramp metering control algorithms are developed for each level of control. Flow-based and lane occupancy-based system algorithms are presented. Detailed data file requirements are provided for each control level. A microcomputer prototype, or laboratory test version of the system level, will be described in a companion project report.
Author: Kwangho Kim
Publisher:
ISBN:
Category : Highway capacity
Languages : en
Pages : 46
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Book Description
Author: Jorge Andrés Laval
Publisher:
ISBN:
Category : Ramp metering (Traffic engineering)
Languages : en
Pages : 42
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Book Description
