Queue Length at Signalized Intersections from Red-Time Formula and the Highway Capacity Manual Compared with Field Data

2017 ◽  
Vol 2615 (1) ◽  
pp. 159-168 ◽  
Author(s):  
Xueying Liu ◽  
Rahim (Ray) F. Benekohal ◽  
Mohammed Abdul Rawoof Shaik
Keyword(s):  
Correction Factor ◽  
Queue Length ◽  
Field Data ◽  
Signalized Intersections ◽  
Highway Capacity ◽  
Significant Discrepancy ◽  
Peak Period ◽  
Highway Capacity Manual ◽  
Lower Volume ◽  
Queue Lengths

This study compared the Highway Capacity Manual 2010 (HCM 2010) procedure (the procedure in HCM 2016 is the same) and the red-time formula (RTF) estimations of the back-of-queue with field data results. The comparisons were made for the 50th and 95th percentile field queue lengths at four signalized intersections along a corridor in one off-peak period and a.m., noon, and p.m. peak periods. For the 50th percentile queue length, the HCM estimates had significant differences from the field data in 52% of the cases (major and minor street cases combined); in 93% of which the HCM overestimated the queue length and in 7% it underestimated the queue length. For the major street, in 28% of the cases the HCM significantly overestimated the queue length on average by 66%, and in 4% of the cases the HCM significantly underestimated on average by 42%. For minor streets, in 70% of the cases the HCM significantly overestimated the queue length on average by 44%, and in 5% of the cases it significantly underestimated on average by 20%. To lower the number of cases with significant discrepancy and to balance the frequency of overestimation and underestimation, a multiplicative correction factor of 0.93 for the major street and 0.78 for the minor streets could be applied to the HCM estimates. For the 95th percentile queue length comparison, in general the HCM presented a better estimation than the RTF. And for minor streets, the RTF tends to overestimate the queue length at higher-volume approaches, while it underestimates at lower-volume approaches. But on a major street with heavier traffic than the minor, such a trend is not clear.

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.

Accounting for Nonrandom Arrivals in Estimate of Delay at Signalized Intersections

1996 ◽  
Vol 1555 (1) ◽  
pp. 9-16 ◽  
Author(s):  
Janice Daniel ◽  
Daniel B. Fambro ◽  
Nagui M. Rouphail
Keyword(s):  
Field Data ◽  
Empirical Studies ◽  
Primary Objective ◽  
Signalized Intersections ◽  
Degree Of Saturation ◽  
Delay Model ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Research Show

The primary objective of this research was to determine the effect of nonrandom or platoon arrivals on the estimate of delay at signalized intersections. The delay model used in the 1994 Highway Capacity Manual (HCM) accounts for nonrandom arrivals through the variable m, which can be shown to be equal to 8kI, where k describes the arrival and service distributions at the intersection and I describes the variation in arrivals due to the upstream intersection. The 1994 HCM delay model m-values are a function of the arrival type, where the arrival type describes the quality of progression at the intersection. Although an improvement to the fixed k I-value used in the 1985 delay model, the 1994 m values are based on empirical studies from limited field data and do not account for the decrease in random arrivals as the volume approaches capacity at the downstream intersection. This research provides an estimate of the variable kI for arterial conditions. An analytical equation was developed as a function of the degree of saturation, and a separate equation was developed for each signal controller type. The results from this research show that the proposed kI's provide delay estimates closer to the measured delay compared with the delay estimates using the kI-values in the 1994 HCM delay model.

scholarly journals Indonesian Highway Capacity Guidance (IHCG) correction factor for signalized intersection

2018 ◽  
Vol 159 ◽  
pp. 01024 ◽  
Author(s):  
Amelia K. Indriastuti ◽  
Eko Yulipriyono
Keyword(s):  
Correction Factor ◽  
Queue Length ◽  
Signalized Intersection ◽  
Performance Parameters ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Traffic Characteristics ◽  
Dependent Variables ◽  
Independent Variable ◽  
Preliminary Study

Indonesian Highway Capacity Guidance or IHCG is a manual developed in 2014 to accommodate traffic characteristics which are no longer appropriate to the preceding manual (Indonesian Highway Capacity Manual or IHCM, established in 1997). From a preliminary study, there are still some differences between theoretical analysis (using IHCG) with the actual conditions. This study aims to obtain IHCG correction factor based on a comparison between predicted performance parameter of a signalized intersection (using IHCG) and measured data, in order to optimize IHCG development. Intersection performance parameters analyzed are the number of queue vehicles (NQ1 and NQ2), and queue length (QL). The model of the correction factor was determined with regression analysis, using DS value as the independent variable, and NQ1, NQ2, or QL differences value as the dependent variables. Implementation of the proposed correction factor of queue length on nearby intersections resulted that the corrected guidance could produce more accurate queue length against measured one by 12% deviation.

Modeling Capacity of Through Movement at Signalized Intersection Affected by Short Left-Turn Bay under Different Signal Settings

2021 ◽  
pp. 036119812110064
Author(s):  
Zihang Wei ◽  
Yunlong Zhang ◽  
Xiaoyu Guo ◽  
Xin Zhang
Keyword(s):  
Cycle Length ◽  
Signalized Intersections ◽  
Signalized Intersection ◽  
Essential Factor ◽  
Highway Capacity ◽  
Left Turn ◽  
Highway Capacity Manual ◽  
Proposed Model ◽  
Vehicle Demand ◽  
The One

Through movement capacity is an essential factor used to reflect intersection performance, especially for signalized intersections, where a large proportion of vehicle demand is making through movements. Generally, left-turn spillback is considered a key contributor to affect through movement capacity, and blockage to the left-turn bay is known to decrease left-turn capacity. Previous studies have focused primarily on estimating the through movement capacity under a lagging protected only left-turn (lagging POLT) signal setting, as a left-turn spillback is more likely to happen under such a condition. However, previous studies contained assumptions (e.g., omit spillback), or were dedicated to one specific signal setting. Therefore, in this study, through movement capacity models based on probabilistic modeling of spillback and blockage scenarios are established under four different signal settings (i.e., leading protected only left-turn [leading POLT], lagging left-turn, protected plus permitted left-turn, and permitted plus protected left-turn). Through microscopic simulations, the proposed models are validated, and compared with existing capacity models and the one in the Highway Capacity Manual (HCM). The results of the comparisons demonstrate that the proposed models achieved significant advantages over all the other models and obtained high accuracies in all signal settings. Each proposed model for a given signal setting maintains consistent accuracy across various left-turn bay lengths. The proposed models of this study have the potential to serve as useful tools, for practicing transportation engineers, when determining the appropriate length of a left-turn bay with the consideration of spillback and blockage, and the adequate cycle length with a given bay length.

Validation Results for Four Models of Oversaturated Freeway Facilities

2000 ◽  
Vol 1710 (1) ◽  
pp. 161-170 ◽  
Author(s):  
Fred L. Hall ◽  
Loren Bloomberg ◽  
Nagui M. Rouphail ◽  
Brian Eads ◽  
Adolf D. May
Keyword(s):  
Field Data ◽  
Simulation Models ◽  
Highway Capacity ◽  
Highway Capacity Manual

Some researchers have noted that the current procedures in the Highway Capacity Manual (HCM) may not be appropriate for analyzing complex or oversaturated freeway facilities. The results of a comparison of an HCM-based procedure with field data from six such freeway sites are reported. Because simulation has often been suggested as an alternative to the HCM for oversaturated freeway facilities, three simulation models (CORSIM, FREQ, and INTEGRATION) were also used to analyze these same six sites. The results suggest that the HCM-based procedures do as well as the three simulation models in reproducing the average speeds across the freeway facilities.

Arrival-Based Uniform Delay Model for Oversaturated Signalized Intersections with Poor Progression

2005 ◽  
Vol 1920 (1) ◽  
pp. 86-94
Author(s):  
Rahim F. Benekohal ◽  
Sang-Ock Kim
Keyword(s):  
Signalized Intersections ◽  
Delay Model ◽  
Adjustment Factor ◽  
Highway Capacity ◽  
New Approach ◽  
Highway Capacity Manual ◽  
Traffic Conditions ◽  
Proposed Model ◽  
Uniform Delay ◽  
Control Delays

For oversaturated traffic conditions, the Highway Capacity Manual (HCM) does not apply a progression adjustment factor to the delay model for signalized intersections when there is an initial queue. This causes counterintuitive results in the calculation of delay; for some cases, delay for a nonzero initial queue condition ends up being less than the delay with zero initial queue conditions. Also, for oversaturated traffic conditions, the delay model in the 2000 edition of HCM yields the same uniform delay values for all arrival types when there is an initial queue. This does not seem reasonable because it ignores the effect of platooning on delay. This paper introduces a new approach for computing uniform delay for oversaturated traffic conditions when progression is poor. This approach directly considers the platooning effects in delay and thus eliminates the need to apply a progression adjustment factor. The proposed model is applicable whether there is an initial queue or not. The approach was validated by a comparison of the control delays obtained from a CORSIM simulation to the delays from the proposed model. Validation procedures were conducted on the basis of zero and nonzero initial queue conditions. The proposed approach resulted in more accurate delay values than the HCM model.

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.

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