Modeling Capacity And Delay At Signalized Intersections With Channelized Right Turn Lanes Considering The Impact Of Blockage
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Modeling Capacity And Delay At Signalized Intersections With Channelized Right Turn Lanes Considering The Impact Of Blockage
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Author : Saeedeh Farivar
language : en
Publisher:
Release Date : 2015
Modeling Capacity And Delay At Signalized Intersections With Channelized Right Turn Lanes Considering The Impact Of Blockage written by Saeedeh Farivar and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with Electronic books categories.
Right-turn channelization is used to improve the capacity at busy intersections with a lot of right-turns. However, under heavy traffic conditions the through lane vehicles might backup and block the right-turn lane. This will affect the discharge rate of right-turning vehicles and reduce the approach capacity and, consequently, increase the approach delay. So if the right-turn channelization is blocked frequently, its advantage is neglected and serious capacity problems can be overlooked. This issue is not addressed in the Highway Capacity Manual (HCM) and no separate model is provided to estimate the capacity and delay of approaches with channelized right-turn lanes. Using conventional methods for estimating the capacity and delay without considering the effect of potential blockage results in overestimation of the approach capacity and underestimation of the approach delay. This research presents probabilistic capacity and delay models for signalized intersections with channelized right-turn lanes considering the possibility of the right-turning vehicles being blocked from accessing the lane. The capacity model was developed by considering the capacity under blockage and non-blockage conditions with respect to the probability of blockage. Subsequently, a model was developed to estimate the probability of blockage. The capacity model is significantly affected by the length of the short-lane section and proportion of right-turn traffic. The proposed capacity model under blockage conditions and also the blockage probability model were validated through VISSIM, a microscopic simulation model. The validation process showed that both models are reliable. For operational purposes, the recommended lengths of the short-lane section were developed which would be useful in evaluating adequacy of the current lengths, identifying the options of extending the short-lane section length, or changing signal timing to reduce the likelihood of blockage. The recommended lengths were developed based on different signal timing plans and several proportions of right-turn traffic. The queue accumulation polygons (QAPs) were used to estimate the approach uniform delay and the HCM procedure was followed for the computation of the incremental delay caused by the random fluctuation of vehicle arrivals. To investigate the effect of blockage on the uniform delay, two different QAPs were developed associated with arrival scenarios under blockage and non-blockage conditions. The proposed delay model was also validated through VISSIM. It was found that, the proposed model can provide accurate estimates of the delay by reflecting the delay increase due to the right-turn channelization blockage. The results showed that the delay of an approach with a channelized right-turn is influenced by the length of the short-lane section and proportion of through and right-turn traffic.
Delay Models At Signalized Intersections Considering Short Right Turn Lanes And Right Turn On Red
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Author : Hongyan Gao
language : en
Publisher:
Release Date : 2011
Delay Models At Signalized Intersections Considering Short Right Turn Lanes And Right Turn On Red written by Hongyan Gao and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with Thesis categories.
The most widely used procedures for estimating delay at signalized intersections are provided by the Highway Capacity Manual (HCM). Despite many revisions, the current HCM delay models lack consideration of short turn lanes and vehicles making a right turn on red (RTOR), both of which are commonly seen in real-life situations. Neglecting the delay caused by short-lane blockages and excluding RTOR traffic, the existing models can underestimate the delay for the signalized intersections. To eliminate these shortcomings of the current HCM, comprehensive delay models were developed by considering the chance of short-lane blockage and right turns proceeding during red. The proposed analytical models were constructed via two different approaches: probabilistic theories and queue accumulation polygons (QAP). They were capable of handling delay estimation given different inputs. The effectiveness and validity of the proposed models were verified by the microscopic simulation model, SimTraffic, which was calibrated based on intersection field data. The proposed models, developed with two different ideologies, showed their distinct advantages. By following the traditional HCM procedures, the probabilistic model only requires basic information as inputs, including traffic volume, saturation flow rate, signal timing plan, and short-lane length. It enhanced the HCM models by being able to handle delay estimation for short right-turn lane and RTOR. By incorporating the RTOR queuing and discharging information, the QAP model overcomes the shortcoming of HCM models where RTOR are directly removed before the capacity or delay analysis. It is better at modeling vehicular arrival and departure for both through and right-turn traffic under various signal control strategies and blockage scenarios. Using the probabilistic model, it was found that the length of the short right-turn lane strongly influences the intersection delay. Delay decreases as the length of the right-turn lane increases. RTOR can reduce the over-saturation, thereby reducing the approach delay substantially, especially when the length of the lane is insufficient to accommodate queuing vehicles. Based on the field data studied in this research, both QAP model and probabilistic model yield better estimates for the approach delay than the HCM model. The results also confirmed that the HCM tends to underestimate the approach delay by ignoring the short-lane blockage and delay contributed by RTOR traffic.
The Validation Of The Highway Capacity Manual Method For Estimating Delay At Actuated Signalized Intersections
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Author : Jason Keeshun Loo
language : en
Publisher:
Release Date : 1994
The Validation Of The Highway Capacity Manual Method For Estimating Delay At Actuated Signalized Intersections written by Jason Keeshun Loo and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1994 with categories.
Modeling The Capacity Of Left Turn And Through Movement Considering Left Turn Blockage And Spillback At Signalized Intersection With Short Left Turn Bay
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Author : Kyoung Min Cho
language : en
Publisher:
Release Date : 2010
Modeling The Capacity Of Left Turn And Through Movement Considering Left Turn Blockage And Spillback At Signalized Intersection With Short Left Turn Bay written by Kyoung Min Cho and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
This research presents more realistic models for left-turn and through volume capacity by taking into account the probabilistic nature of the left-turn bay blockages and spillbacks at a signalized intersection under the leading phasing scheme with a short left-turn bay. Generally, the left-turn bay spillback situation has been overlooked in the leading left-turn signal because much attention has been given to the more common problem of left-turn blockage under the leading left signal. The left-turn spillback situation, however, might happen because the ratio of left-turning vehicle tends to be relatively high in the traffic after the occurrence of left-turn bay blockage. That is, left-turn bay blockage, spillback situations, left-turn capacity, and through capacity are closely connected with one another. Hence, this research estimates more precisely the capacity for through and left-turn movement by considering the left-turn bay blockage and spillback situations associated with left-turn bay under leading left-turn signal operations. In order to find general agreement between the results from this proposed model and a real-world situation, the developed capacity model is validated with the results from CORSIM simulations of a real-world signalized intersection. The binomial distribution is applied as the arrival distribution for through movement considering the characteristics of expected arrivals under heavy flow conditions. Finally, since left-turn bay blockage and spillback situation seem to have adverse impacts on each other, this research investigates if there are any dependent relationships between left-turn bay blockage and spillback. Here, this study confirmed that close relationships between left-turn bay blockage and spillback situations obviously exists.
Traffic Operations At All Way Stop Controlled Intersections Estimating Capacity And Delay At An All Way Stop Controlled Intersection
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Author :
language : en
Publisher:
Release Date : 1990
Traffic Operations At All Way Stop Controlled Intersections Estimating Capacity And Delay At An All Way Stop Controlled Intersection written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1990 with Electronic traffic controls categories.
Improving Highway Travel Time Estimation In Fsutms By Considering Intersection Delays
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Author : Fang Zhao
language : en
Publisher:
Release Date : 2006
Improving Highway Travel Time Estimation In Fsutms By Considering Intersection Delays written by Fang Zhao and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with Roads categories.
Modeling Of Delay Induced By Downstream Traffic Disturbances At Signalized Intersection
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Author : Kamran Ahmed
language : en
Publisher:
Release Date : 2006
Modeling Of Delay Induced By Downstream Traffic Disturbances At Signalized Intersection written by Kamran Ahmed and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with Roads categories.
A Delay Model For Exclusive Right Turn Lanes At Signalized Intersections With Uniform Arrivals And Right Turns On Red
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Author : Mohammad A. Qureshi
language : en
Publisher:
Release Date : 2000
A Delay Model For Exclusive Right Turn Lanes At Signalized Intersections With Uniform Arrivals And Right Turns On Red written by Mohammad A. Qureshi and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2000 with categories.
Assessing The Value Of Model Calibration For Signalized Intersection
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Author :
language : en
Publisher:
Release Date : 2004
Assessing The Value Of Model Calibration For Signalized Intersection written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with categories.
The Highway Capacity Manual (HCM) provides the most widely used methodologies for evaluating the quality of service on highway and street facilities. However, many users contend that the HCM models they are using are not accurate in emulating some real world conditions. In this thesis, the HCM control delay model for signalized intersections is assessed to identify where and when such deficiencies occur. Four signalized intersections within the Chicago central business district (CBD) area are selected to assess the accuracy of the HCM control delay model. The lane groups studied include three through lane groups and one permissive left-turn lane group. Input data (e.g. lane group volumes, proportion of vehicles arriving on green, effective green time, etc.) for the HCM model and empirical data (e.g. actual measured control delay) were collected cycle by cycle in the field. Saturation flow rates estimated from (a) the HCM default parameter values, (b) field calibration and (c) statistical optimization are entered into the HCM control delay model, respectively, to calculate control delays. Then, the control delays calculated from the model are contrasted to those measured from the field. For the through lane groups, the analysis indicates that the control delay calculated using the HCM default parameter values overestimates field delay in most of cases, and it may not accurately reflect the lane groups' performance. However, when field calibrated and/or optimized values are used, the control delay estimated using the model is close to that obtained from field measurements, and this indicates that the HCM control delay model is reliable. For the permissive left-turn lane group, no matter which values of saturation flow rate are used, the control delay estimated using the HCM model is not comparable with that obtained from field measurements due to the small sample size of the number of vehicles arriving per cycle, and other factors apparently not reflected in the delay.
Impact Of Lane Drops On Intersection Capacity
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Author :
language : en
Publisher:
Release Date : 2004
Impact Of Lane Drops On Intersection Capacity written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with categories.
Lane drops downstream of signalized intersections are found on many urban and suburban streets and highways. The short lane is typically under-utilized at the intersection since drivers avoid using the short lane due to the potential for stressful merges downstream of the signal. This unconventional geometric configuration downstream of the lane drop intersection affects intersection capacity and operations. The current Highway Capacity Manual (HCM) does not take into account downstream lane drop conditions, thereby resulting in significant discrepancy between the HCM defaults and field observed lane utilization factors (LUF). The primary objectives of this research were to identify whether and by how much lane drops affect performance of actuated signalized intersections under various traffic demand levels and lane drop geometries. The research developed LUF prediction models by intersection type from data on traffic, signal and intersection geometry collected in the field. The developed models imply that the downstream lane length and traffic intensity are positively correlated with the LUF and that other geometric variables at the approach may also influence lane utilization. Also, a traffic simulation model was used to quantify the impact of lane drops on intersection operations with various traffic volumes and geometric conditions. Through the simulation, it was found that additional green time, which should reduce delay, was created because of the overloaded full lane at the approach, however; a higher probability of green time termination with maximum green time dominates the benefit of extra green and the approach gains significant extra delays. Based on the data obtained from the simulation, this research quantified the amount of additional delay for the subject movement and established delay adjustment factors due to account for lane drop effects. Findings from this research are expected to contribute to the assessment of lane drop intersection performance.