Capacity and Queue Modeling for On-Ramp–Freeway Junctions

2003 ◽  
Vol 1852 (1) ◽  
pp. 256-264 ◽  
Author(s):  
Marina Albanese ◽  
Roberto Camus ◽  
Giovanni Longo
Keyword(s):  
Main Line ◽  
Highway Capacity ◽  
Total Delay ◽  
Traffic Dynamics ◽  
Highway Capacity Manual ◽  
Traffic Volumes ◽  
First Results ◽  
Measures Of Effectiveness ◽  
Gap Acceptance Theory

With reference to the procedure in the Highway Capacity Manual (HCM) 2000 for estimation of measures of effectiveness, a model is proposed to estimate merge-area capacity and to predict traffic dynamics and queue evolution for on-ramp–freeway junctions. The aims of the study are to analyze the behavior of flows within the merge area and to propose a methodology to dynamically estimate the capacity of both ramp and main line according to inflow patterns and to develop a mesoscopic model of merge facilities that allows the prediction of merge-area traffic outflow according to inflow patterns and to estimate traffic queue dynamics. The most relevant finding of the study is a methodology for estimation of the capacity of the merge area referred separately to both the main line and the ramp. The proposed approach could be considered as a link between the HCM hypotheses and those of gap-acceptance theory; the capacity of the competitive streams within the merge area depends on the opposing traffic volumes. The model gives information about traffic flows and queue dynamics (including total delay and maximum queue length). The first results of the application to a case study are briefly discussed, and some further developments are suggested.

Validation of Generalized Delay Model for Vehicle-Actuated Traffic Signals

1997 ◽  
Vol 1572 (1) ◽  
pp. 105-111 ◽  
Author(s):  
Nagui M. Rouphail ◽  
Mohammad Anwar ◽  
Daniel B. Fambro ◽  
Paul Sloup ◽  
Cesar E. Perez
Keyword(s):  
North Carolina ◽  
Field Data ◽  
Traffic Signals ◽  
Signalized Intersections ◽  
Delay Model ◽  
Highway Capacity ◽  
Generalized Model ◽  
Highway Capacity Manual ◽  
Traffic Volumes ◽  
Isolated Intersection

One limitation of the Highway Capacity Manual (HCM) model for estimating delay at signalized intersections is its inadequate treatment of vehicle-actuated traffic signals. For example, the current delay model uses a single adjustment for all types of actuated control and is not sensitive to changes in actuated controller settings. The objective in this paper was to use TRAF-NETSIM and field data to evaluate a generalized delay model developed to overcome some of these deficiencies. NETSIM was used to estimate delay at an isolated intersection under actuated control, and the delay values obtained from NETSIM were then compared with those estimated by the generalized delay model. In addition, field data were collected from sites in North Carolina, and delays observed in the field were compared with those estimated by the generalized delay model. The delays estimated by the generalized model were comparable with the delays estimated by NETSIM. The data compared favorably for degrees of saturation of less than 0.8. However, at higher degrees of saturation, the generalized model produced delays that were higher than NETSIM’s. Some possible explanations for this discrepancy are discussed. The delays estimated by the generalized model were comparable with delays observed in the field. Researchers have concluded that the generalized delay model is sensitive to changes in traffic volumes and vehicle-actuated controller settings and that the generalized delay model is much improved over the current HCM model in estimating delay at vehicle-actuated traffic signals.

scholarly journals Capacity of Advance Right-Turn Motorized Vehicles at Signalized Intersections for Mixed Traffic Conditions

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Bing Li ◽  
Wei Cheng ◽  
Yiming Bie ◽  
Bin Sun
Keyword(s):  
Arrival Rate ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Traffic Conditions ◽  
Capacity Model ◽  
Conflict Zone ◽  
Traffic Conflict ◽  
Motorized Vehicles ◽  
The Relationship ◽  
Gap Acceptance Theory

Right-turn motorized vehicles turn right using channelized islands, which are used to improve the capacity of intersections. For ease of description, these kinds of right-turn motorized vehicles are called advance right-turn motorized vehicles (ARTMVs) in this paper. The authors analyzed four aspects of traffic conflict involving ARTMVs with other forms of traffic flow. A capacity model of ARTMVs is presented here using shockwave theory and gap acceptance theory. The proposed capacity model was validated by comparison to the results of the observations based on data collected at a single intersection with channelized islands in Kunming, the Highway Capacity Manual (HCM) model and the VISSIM simulation model. To facilitate engineering applications, the relationship describing the capacity of the ARTMVs with reference to the distance between the conflict zone and the stop line and the relationship describing the capacity of the ARTMVs with reference to the effective red time of the nonmotorized vehicles moving in the same direction were analyzed. The authors compared these results to the capacity of no advance right-turn motorized vehicles (NARTMVs). The results show that the capacity of the ARTMVs is more sensitive to the changes in the arrival rate of nonmotorized vehicles when the arrival rate of the nonmotorized vehicles is 500  (veh/h)~2000  (veh/h) than when the arrival rate is some other value. In addition, the capacity of NARTMVs is greater than the capacity of ARTMVs when the nonmotorized vehicles have a higher arrival rate.

scholarly journals A Novel Methodology for Estimating the Capacity and Level of Service for the New Mega Elliptical Roundabout Intersection

2020 ◽  
Vol 2020 ◽  
pp. 1-18 ◽  
Author(s):  
Ahmed I. Z. Mohamed ◽  
Yusheng Ci ◽  
Yiqiu Tan
Keyword(s):  
Geometric Design ◽  
Level Of Service ◽  
Highway Capacity ◽  
Operation Performance ◽  
Highway Capacity Manual ◽  
Federal Highway ◽  
Green Book ◽  
Traffic Operation ◽  
Gap Acceptance Theory ◽  
Better Than

Mega elliptical roundabout is a new intersection on rural multilane highways. This intersection was developed in a previous paper using simulation data, and the authors found that it is better than interchange (full cloverleaf) in most scenarios of traffic flow. Basically, there are no guidelines or procedures for designing mega elliptical roundabout in AASHTO Green Book, Federal Highway Administration guides, and Highway Capacity Manual. Thus, the purpose of this study is to analyze the traffic operation performance and propose a methodology for calculating the capacity of mega elliptical roundabout and also the level of service by gap acceptance theory. Moreover, this research studied the influence of different values of truck ratios and also different values of a major highway speed on geometric design and traffic operation performance for mega elliptical roundabout. To validate the thoroughness of the proposed methodology, VISSIM simulations were conducted. This research will assist practitioners in determining the appropriate geometric design, assessing mega elliptical roundabout intersections, and making comparisons with other alternatives.

scholarly journals Vehicle and Pedestrian Level of Service in Street Designs with Elements of Shared Space

2020 ◽  
Vol 2674 (9) ◽  
pp. 1084-1096
Author(s):  
Ioannis Kaparias ◽  
Rui Wang
Keyword(s):  
Video Data ◽  
Road User ◽  
Level Of Service ◽  
Highway Capacity ◽  
Vehicle Traffic ◽  
Highway Capacity Manual ◽  
Shared Space ◽  
Before And After ◽  
Traffic Volumes

Inspired by developments in urban planning, the concept of “shared space” has recently emerged as a way of creating a better public realm. This is achieved through a range of streetscape treatments aimed at asserting the function of streets as places by facilitating pedestrian movement and lowering vehicle traffic volumes and speeds. The characteristics of streets with elements of shared space point to the conjecture that traffic conditions and road user perceptions may be different to those on streets designed according to more conventional principles, and this is likely to have an impact on the quality of service. The aim of this paper is, therefore, to perform an analysis in relation to level of service (LOS) and to investigate how this may change as a result of the implementation of street layouts with elements of shared space. Using video data from the Exhibition Road site in London during periods before and after its conversion from a conventional dual carriageway to a layout featuring several elements of shared space, changes in relation to LOS for both vehicle traffic and pedestrians are investigated, by applying the corresponding methods from the 2010 Highway Capacity Manual. The results suggest that streets with elements of shared space provide a much improved pedestrian experience, as expressed by higher LOS ratings, but without compromising the quality of vehicle traffic flow, which, in fact, also sees slight improvements.

Saturation Flow and Capacity of Shared Lanes: Comparative Evaluation of Estimation Methods

1996 ◽  
Vol 1555 (1) ◽  
pp. 50-58
Author(s):  
G. A. Glannopoulos ◽  
Muhammad A. S. Mustafa
Keyword(s):  
Flow Rate ◽  
Comparative Evaluation ◽  
Field Measurements ◽  
Estimation Methods ◽  
Highway Capacity ◽  
Operational Conditions ◽  
Highway Capacity Manual ◽  
Traffic Volumes ◽  
Saturation Flow Rate ◽  
Saturation Flow

The operation of shared lanes, especially in the case of permitted phasing control, is still considered a complicated task and one for which many procedures and methods have been introduced. Dealt with here is the complexity when left- or right-turn movements or both are made during the unsaturated part of the opposing traffic flow. Three main methods used for estimating the shared lane's saturation flow rate and capacity values—that used in the 1985 Highway Capacity Manual (HCM) and the Australian Road Research Board (ARRB) and the Canadian methods—were analyzed and evaluated. The methodology for the comparative evaluation was based on two main approaches. In the first approach, example 1 of Chapter 9 of the HCM was used as a case study in which left through and left through right shared lanes exist in permitted phase control. In this case several computer runs were performed using the programs SIDRA and SINTRAL to estimate saturation flow and capacity values of the shared lanes opposed by different traffic volumes of the conflicting movements. Results of this approach showed that the 1985 HCM and ARRB methods are fairly close in estimating saturation flow and capacity, whereas the Canadian method gave considerably different results. Analysis showed that the sensitivity of the Canadian method to estimate saturation flow rates of the shared lane in cases of different levels of opposing traffic was an average of 10 times higher than the average of the two other methods, which were very close in their estimation of levels of opposing traffic volumes. In the second approach, field measurements of saturation flow rate values of shared lanes at different locations and operational conditions were compared with the values estimated by the three methods under the same conditions. Results, based on field observations, revealed that the Canadian method estimates of saturation flow were always lower than the measured values. At low saturation flow values, HCM estimates were slightly higher than the observed values; however, at higher saturation flow rate values. HCM estimates closely matched the observed ones. The ARRB method estimates were quite close to the observed saturation flow values under all of the different conditions considered in the field observation task.

Comparison of Queue-Length Models at Signalized Intersections

2000 ◽  
Vol 1710 (1) ◽  
pp. 222-230 ◽  
Author(s):  
Fadhely Viloria ◽  
Kenneth Courage ◽  
Donald Avery
Keyword(s):  
Queue Length ◽  
Theoretical Models ◽  
Traffic Signals ◽  
Comprehensive Treatment ◽  
Highway Capacity ◽  
Left Turn ◽  
Highway Capacity Manual ◽  
Classification Framework ◽  
Queue Model ◽  
Measures Of Effectiveness

Several measures of effectiveness (MOEs) are associated with the queuing process at traffic signals, including delay, number of stops, fuel consumption, emissions, and queue length. The focus in this study is on queue length in general and on the storage requirements for left turns in particular. Queue length is an important MOE because queues that overflow the available storage space have an adverse effect on the overall operation of the intersection. Many traffic models now provide queue-length estimates, but the procedures used by these models are based on different queue definitions and have different computational approaches that lead to different results. A classification framework is developed for the existing models, their behavior is compared with that of the proposed Highway Capacity Manual (HCM) 2000 queue model, and queue conversion factors are provided for translating the various model outputs to their HCM 2000 equivalent. The proposed HCM 2000 model and its parent model from the Signalized and Unsignalized Intersection Design and Research Aid (SIDRA) provide a comprehensive treatment of the queuing process, accounting for control parameters such as controller type and progression quality as well as for the random and overflow effects associated with traffic flow. As such, the queue-length estimates from these models are more analytically defensible than those of the simpler theoretical models. The SIDRA and HCM 2000 queue estimates are generally higher than those of most other models and are somewhat higher than what conventional wisdom would suggest. It is suggested as a result of the comparisons presented that the queue estimates from some models are unduly optimistic when demand approaches capacity and that a goal of 90 percent confidence in the adequacy of left-turn storage lanes may be difficult to achieve under these conditions.

Operational Analysis of a Single-Lane Roundabout with a Mix of Driverless Vehicles

2017 ◽  
Vol 2615 (1) ◽  
pp. 123-131
Author(s):  
Liang Shi ◽  
Panos D. Prevedouros
Keyword(s):  
Sensitivity Analyses ◽  
Gap Acceptance ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Control Delay ◽  
Operational Analysis ◽  
Traffic Composition ◽  
Acceptance Model ◽  
Traffic Operation

Driverless cars (DLCs) are vehicles capable of managing several driving tasks by themselves under different degrees of human intervention. DLCs are able to maintain shorter headways in entering a roundabout and circulating in the roundabout. The Highway Capacity Manual (HCM) provides a regression-based gap acceptance model for estimating the capacity of roundabouts. The gap acceptance model captures driver behavior, which is characterized by headways. As automotive manufacturers and technology companies develop driverless capabilities for roadway vehicles, DLCs at various traffic compositions will likely have different effects on the traffic operation of roundabouts. This paper presents the operational analysis for a single-lane roundabout with driverless vehicles under different traffic compositions. Considering the uncertainty of the technological capabilities and the legal and behavioral acceptability of DLCs, sensitivity analyses were conducted. The simulation results for one sample case study show that when the roundabout operates at a Level of Service B (LOS B) or better, DLCs will not have an effect on either the capacity or the control delay. A reduction in control delay will occur when DLCs are set with shorter headways (as assumed for the connected DLC) under low traffic composition (1% to 10%) on a single-lane roundabout operating near capacity. When the share is below 1%, the effect of DLCs is very small. When the LOS of the roundabout approaches E, more reduction in delay is expected when the portion of DLCs in traffic increases.

MIDBLOCK U–TURN FACILITIES ON MULTILANE DIVIDED HIGHWAYS: AN ASSESSMENT OF DRIVER’S MERGING GAP AND STOP DELAYS

2015 ◽  
Vol 76 (14) ◽  
Author(s):  
Othman Che Puan ◽  
Che Ros Ismail ◽  
Mohd Rosli Hainin ◽  
Anil Minhans ◽  
Nur Syahriza Muhamad Nor
Keyword(s):  
Road Traffic ◽  
Video Recording ◽  
Primary Objective ◽  
Major Road ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Critical Gap ◽  
Planning And Design ◽  
Traffic Delays ◽  
Traffic Volumes

This paper discusses the results of a study which was carried out with a primary objective to evaluate the merging gaps and traffic delays at midblock U–turn facilities installed on multilane divided highways. A total of more than 2,000 U–turn drivers at a midblock U–turn facility on an urban multilane highway were observed using a camera–video recording technique. The data pertaining to the analysis of gap acceptance and rejection was abstracted from the video–playbacks using a computer event recording program. The analysis found that the critical gap of the drivers at a midblock U–turn facility is in the range of 4.0 – 4.5 seconds, which is different from the values reported for studies carried out in other countries. The effect of major road traffic volumes on the stop delays to the U–turn drivers could not be established because the data did not exhibit any specific trend. The drivers were observed to make forced merging maneuvers when traffic volumes in the main traffic stream are relatively heavy. Such maneuvers lead to flow breakdown in the major road to occur at a faster rate. The findings suggest that there is a need for a thorough study to be carried out to evaluate the current practice of U–turn facility design and assessment methods since traffic operations at such a facility is different from those at on–ramp facilities where their planning and design are generally based on the American Highway Capacity Manual. 

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