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.

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.

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.

Validation of Generalized Delay Model for Oversaturated Conditions

1997 ◽  
Vol 1572 (1) ◽  
pp. 122-130 ◽  
Author(s):  
Roelof J. Engelbrecht ◽  
Daniel B. Fambro ◽  
Nagui M. Rouphail ◽  
Aladdin A. Barkawi
Keyword(s):  
Simulation Model ◽  
Close Agreement ◽  
Signalized Intersections ◽  
Delay Model ◽  
Traffic Operations ◽  
Microscopic Simulation ◽  
Highway Capacity ◽  
Traffic Demand ◽  
Highway Capacity Manual ◽  
The U.S

With today’s ever-increasing traffic demand, more and more signalized intersections are experiencing congestion for longer periods of time. To better quantify oversaturated conditions, it is necessary to accurately estimate oversaturation delay. The generalized delay model, proposed for inclusion in the next update of the U.S. Highway Capacity Manual (HCM), is introduced here. The generalized delay model differs from the model in the 1994 edition of the HCM as it is sensitive to the duration of the analysis period and is not restricted to degrees of saturation less than 1.2. The TRAF-NETSIM microscopic simulation model was used to verify the generalized delay equation for oversaturated conditions. A simulation model was used, because it is extremely difficult to measure oversaturated delay in the field. The study was designed to cover as much of the domain of oversaturated traffic operations as possible. The variability in simulated delays was investigated, and an equation was developed to predict the standard deviation of oversaturated delay estimates. It was found that delays estimated by the proposed generalized delay model are in close agreement with those simulated by TRAF-NETSIM. On average, simulated delays are overestimated slightly, but the error is small compared with actual delays. The proposed generalized delay model is expected to provide a good estimate of actual oversaturation delays that occur in the field.

scholarly journals Evaluation of the Quality of Service of Pedestrian Flows on a Signalized Intersections

2019 ◽  
Vol 65 (2) ◽  
pp. 37-42
Author(s):  
Vuk Bogdanović ◽  
Nemanja Garunović ◽  
Valentina Basarić ◽  
Jelena Mitrović Simić
Keyword(s):  
Quality Of Service ◽  
Signalized Intersections ◽  
Highway Capacity ◽  
Local Conditions ◽  
Highway Capacity Manual ◽  
Traffic Conditions ◽  
Novi Sad ◽  
First Time

In 5th edition of Highway Capacity Manual (2010) the methodology for evaluating the quality of service provided to pedestrians traveling through a signalized intersection first time was shown. The same methodology has been retained in the latest edition of the aforementioned manual. Provided methodology include determination of the key parameters for evaluation the quality of service of pedestrian flows on signalized intersections. In this paper mentioned methodology was shown through the short procedural steps. In order to verify the possibility of applying this procedure in local conditions, an analysis of traffic conditions at an intersection in Novi Sad was performed as an example.

Predicting Lane-by-Lane Flows and Speeds for Freeway Segments

2020 ◽  
Vol 2674 (9) ◽  
pp. 1052-1068
Author(s):  
Fabio Sasahara ◽  
Luan Guilherme Staichak Carvalho ◽  
Tanay Datta Chowdhury ◽  
Zachary Jerome ◽  
Lily Elefteriadou ◽  
...  
Keyword(s):  
Field Data ◽  
Performance Estimation ◽  
Free Flow ◽  
Highway Capacity ◽  
Distribution Models ◽  
Highway Capacity Manual ◽  
Speed Flow ◽  
Flow Speeds ◽  
The Relationship

The Highway Capacity Manual is a major reference for evaluating the capacity and quality of service of road facilities. However, it holds the assumption that lanes perform equally, which can result in inaccuracies in performance estimation. The main purpose of this research is to develop a series of models for estimating flows and speeds by lane for various types of freeway segments, including basic, merge, and diverge types. These models consider the demand-to-capacity ratio, the presence of trucks, grade, and the presence of upstream and downstream ramps. To predict lane performance effectively, it is critical that capacity and free-flow speeds are also determined for individual lanes. Therefore, this study also investigates the relationship between segment average values and lane values for free-flow speeds and capacities, and proposes a method to estimate these parameters for each lane as a function of the segment average. Observed field data has shown that free-flow speeds and capacities have lowest values on the shoulder lanes and highest values on the median lanes. Speed and flow data were collected from 48 segments throughout the U.S.A., including basic, merge, and diverge segments, to develop flow and speed distribution models. A case example is provided to illustrate the application of the developed model and the predicted speed–flow relationship is compared with field data, with satisfactory results.

Effects of Parameter Distributions and Correlations on Uncertainty Analysis of Highway Capacity Manual Delay Model for Signalized Intersections

2005 ◽  
Vol 1920 (1) ◽  
pp. 118-124 ◽  
Author(s):  
Xiaojin Ji ◽  
Panos D. Prevedouros
Keyword(s):  
Uncertainty Analysis ◽  
Confidence Intervals ◽  
Probability Distributions ◽  
Input Parameter ◽  
Major Effect ◽  
Degree Of Saturation ◽  
Delay Model ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Input Parameters

The uncertainty analysis of the Highway Capacity Manual (HCM) delay model often assumes parameter variances and distributions. In light of the difficulty in specifying distributions and estimating correlations, the present study investigated (a) the possibility of assumed distributions’ major effect on the results and (b) the effects of correlations on the accuracy of delay estimates. Field data from one intersection approach in Hawaii and nine intersection approaches in Illinois were used. All input variables in the delay model except for the analysis period were considered uncertain; the analysis period remained fixed at 15 min for consistency with HCM. The simulation results showed that the confidence intervals of delay can be large even if the variability of each input parameter is small. The degree of saturation (X) has a significant effect on the uncertainty of delay estimates for X values 0.9. The standard deviation of input parameters is the main factor affecting the uncertainty of delay estimates. The probability distributions have a slight effect. Correlations among input parameters are often overlooked, but they have a significant effect on the confidence intervals of delay estimates, especially when the variability of the input parameters is large and the input parameters are highly correlated. The frequency distribution of delay estimates is not normal; the shifted lognormal distribution provides a better statistical fit.

Comparison of Methods for Sensitivity and Uncertainty Analysis of Signalized Intersections Analyzed with the Highway Capacity Manual

2005 ◽  
Vol 1920 (1) ◽  
pp. 56-64 ◽  
Author(s):  
Xiaojin Ji ◽  
Panos D. Prevedouros
Keyword(s):  
Uncertainty Analysis ◽  
Confidence Intervals ◽  
Signalized Intersections ◽  
Sensitive Volume ◽  
Delay Model ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Point Estimate Method ◽  
Analysis Methods ◽  
Sensitivity And Uncertainty Analysis

Most users of the Highway Capacity Manual (HCM) would prefer to have confidence intervals around the estimate of delay, but no procedure measures the uncertainty in delay and level of service. Four sensitivity analysis methods-partial differential analysis (PDA), partial correlation coefficient analysis, standardized regression coefficient analysis, and the Fourier amplitude sensitivity test (FAST)-and four uncertainty analysis methods-first-order analysis (FOA), Monte Carlo simulation (MCS), FAST, and the point estimate method (PEM)-were investigated. They were applied to data from an actuated signalized intersection. All input variables in the delay model except for the duration of analysis period were considered uncertain, for consistency with HCM. Day-to-day variation was the source of errors. Progression factor, cycle length, green time, and saturation flow are the most sensitive parameters. The incremental delay and upstream metering factors are the least sensitive. Volume and peak hour factor fall in between. The four uncertainty methods produced similar results for the mean, standard deviation, and confidence intervals of control delay for the base case. When the standard deviations of input parameters were doubled, MCS, FAST, and PEM produced similar results. PDA and FOA appear to be less suitable for sensitivity and uncertainty analysis, respectively, of the HCM delay model for signalized intersections.

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.

Generalized Delay Model for Signalized Intersections and Arterial Streets

1997 ◽  
Vol 1572 (1) ◽  
pp. 112-121 ◽  
Author(s):  
Daniel B. Fambro ◽  
Nagui M. Rouphail
Keyword(s):  
Performance Measure ◽  
Signalized Intersections ◽  
Level Of Service ◽  
Delay Model ◽  
Highway Capacity ◽  
Average Delay ◽  
Variable Demand ◽  
Highway Capacity Manual ◽  
Arterial Streets ◽  
Proposed Model

Average delay per vehicle is the primary measure for determining the level of service at signalized intersections. This performance measure is also a major component in the calculation of average travel speed used to determine the level of service on arterial streets. The most widely used models for estimating delay at signalized intersections are those in Chapters 9 ("Signalized Intersections") and 11 ("Urban and Suburban Arterials") of the Highway Capacity Manual. This research reviewed the literature on models for estimating delay at signalized intersections to identify limitations and formulate revised models to address those limitations. Specific problems that were addressed included the inability to account for actuated-control parameters, oversaturation and variable demand, and metering and filtering by upstream traffic signals. The research team developed a generalized delay model to address these limitations and then validated the generalized model with both field and simulation data. The proposed model is sensitive to actuated-control parameter settings, oversaturation and variable demand conditions, and filtering and metering effects of upstream signals. The proposed model is also a good predictor of delays observed in the field and estimated by microscopic traffic simulation programs for the conditions studied. The generalized delay model is recommended for inclusion in future editions of the Highway Capacity Manual.

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.

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