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.

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.

Seismic hazard sensitivity analysis: A multi-parameter approach

1991 ◽  
Vol 81 (3) ◽  
pp. 796-817
Author(s):  
Nitzan Rabinowitz ◽  
David M. Steinberg
Keyword(s):  
Sensitivity Analysis ◽  
Seismic Hazard ◽  
Subjective Probability ◽  
Probability Distributions ◽  
Input Parameter ◽  
The Other ◽  
Probabilistic Assessment ◽  
Input Parameters ◽  
Parameter Approach

Abstract We propose a novel multi-parameter approach for conducting seismic hazard sensitivity analysis. This approach allows one to assess the importance of each input parameter at a variety of settings of the other input parameters and thus provides a much richer picture than standard analyses, which assess each input parameter only at the default settings of the other parameters. We illustrate our method with a sensitivity analysis of seismic hazard for Jerusalem. In this example, we find several input parameters whose importance depends critically on the settings of other input parameters. This phenomenon, which cannot be detected by a standard sensitivity analysis, is easily diagnosed by our method. The multi-parameter approach can also be used in the context of a probabilistic assessment of seismic hazard that incorporates subjective probability distributions for the input parameters.

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.

scholarly journals Capacity and Delay Estimation for Roundabouts Using Conflict Theory

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Zhaowei Qu ◽  
Yuzhou Duan ◽  
Hongyu Hu ◽  
Xianmin Song
Keyword(s):  
Queuing Theory ◽  
High Volume ◽  
Conflict Theory ◽  
Model Parameters ◽  
Delay Model ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Traffic Characteristics ◽  
Capacity Model ◽  
Proposed Model

To estimate the capacity of roundabouts more accurately, the priority rank of each stream is determined through the classification technique given in the Highway Capacity Manual 2010 (HCM2010), which is based on macroscopical analysis of the relationship between entry flow and circulating flow. Then a conflict matrix is established using the additive conflict flow method and by considering the impacts of traffic characteristics and limited priority with high volume. Correspondingly, the conflict relationships of streams are built using probability theory. Furthermore, the entry capacity model of roundabouts is built, and sensitivity analysis is conducted on the model parameters. Finally, the entrance delay model is derived using queuing theory, and the proposed capacity model is compared with the model proposed by Wu and that in the HCM2010. The results show that the capacity calculated by the proposed model is lower than the others for an A-type roundabout, while it is basically consistent with the estimated values from HCM2010 for a B-type roundabout.

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 PENGARUH SUKARELAWAN PENGATUR LALU LINTAS TERHADAP KINERJA SIMPANG TAK BERSINYAL GANESHA SURAKARTA

2019 ◽  
Vol 19 (2) ◽  
pp. 133-142
Author(s):  
Gus Maelan Irfana ◽  
Nurul Hidayati ◽  
Sri Sunarjono
Keyword(s):  
Traffic Control ◽  
Traffic Congestion ◽  
Motor Vehicle ◽  
Positive Influence ◽  
Degree Of Saturation ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
The Road ◽  
On The Road ◽  
The City

Abstract Traffic congestion in the City of Surakarta gave rise to a phenomenal figure among motor vehicle drivers, called the Traffic Control Volunteers or abbreviated as Supeltas. This Supeltas is present on the road to help organize the movement of traffic, as happened at the Surakarta Ganesha Unsignalized Intersection. This study aims to determine the influence of the existence of Supeltas on capacity, degree of saturation, delay, and queuing opportunities that occur at the intersection. The analysis was carried out using the 1997 Indonesian Highway Capacity Manual. The results showed that the intersection without Supeltas had a capacity of 3,114.03 pcu/hour and a degree of saturation of 1.47, while the same intersection but with Supeltas had a capacity of 3,136.81 pcu/hour and a degree of saturation of 1.51. These results indicate that Supeltas has a positive influence on the performance of the intersection. Nevertheless, the degree of saturation in the location increased due to the increase in traffic volume as well as increased capacity. Keywords: unsignalized intersection, intersection performance, intersection capacity, degree of saturation  Abstrak Kemacetan lalu lintas di Kota Surakarta memunculkan sosok fenomenal di kalangan pengendara kendaraan bermotor, yang disebut Sukarelawan Pengatur Lalu Lintas atau disingkat Supeltas. Supeltas ini hadir di jalan untuk membantu mengatur pergerakan lalu lintas, seperti yang terjadi di Simpang Tak Bersinyal Ganesha Surakarta. Penelitian ini bertujuan untuk menentukan pengaruh keberadaan Supeltas terhadap kapasitas, derajat kejenuhan, tundaan, dan peluang antrian yang terjadi di simpang tersebut. Analisis dilakukan dengan menggu-nakan Manual Kapasitas Jalan Indonesia 1997. Hasil analisis menunjukkan bahwa simpang tanpa Supeltas memiliki kapasitas sebesar 3.114,03 smp/jam dan derajat kejenuhan 1,47, sedangkan simpang yang sama tetapi dengan Supeltas memiliki kapasitas sebesar 3.136,81 smp/jam dan derajat kejenuhan 1,51. Hasil tersebut menunjukkan bahwa Supeltas mempunyai pengaruh positif terhadap kinerja simpang. Meskipun demikian, derajat kejenuhan di lokasi tersebut meningkat karena bertambahnya volume lalu lintas di samping kapasitas yang juga meningkat. Kata-kata kunci: simpang tak bersinyal, kinerja simpang, kapasitas simpang, derajat kejenuhan

scholarly journals Travel Time Estimation on Urban Street Segment

2018 ◽  
Vol 30 (1) ◽  
pp. 115-120 ◽  
Author(s):  
Jelena Kajalić ◽  
Nikola Čelar ◽  
Stamenka Stanković
Keyword(s):  
Travel Time ◽  
Time Estimation ◽  
Travel Speed ◽  
Degree Of Saturation ◽  
Level Of Service ◽  
Travel Time Estimation ◽  
Highway Capacity ◽  
Local Conditions ◽  
Highway Capacity Manual ◽  
Urban Streets

Level of service (LOS) is used as the main indicator of transport quality on urban roads and it is estimated based on the travel speed. The main objective of this study is to determine which of the existing models for travel speed calculation is most suitable for local conditions. The study uses actual data gathered in travel time survey on urban streets, recorded by applying second by second GPS data. The survey is limited to traffic flow in saturated conditions. The RMSE method (Root Mean Square Error) is used for research results comparison with relevant models: Akcelik, HCM (Highway Capacity Manual), Singapore model and modified BPR (the Bureau of Public Roads) function (Dowling - Skabardonis). The lowest deviation in local conditions for urban streets with standardized intersection distance (400-500 m) is demonstrated by Akcelik model. However, for streets with lower signal density (<1 signal/km) the correlation between speed and degree of saturation is best presented by HCM and Singapore model. According to test results, Akcelik model was adopted for travel speed estimation which can be the basis for determining the level of service in urban streets with standardized intersection distance and coordinated signal timing under local conditions.

scholarly journals Uncertainty Analysis and Characterization of the SOFAST Mirror Facet Characterization System

2011 ◽  
Author(s):  
Nolan S. Finch ◽  
Charles E. Andraka
Keyword(s):  
Uncertainty Analysis ◽  
Focal Length ◽  
Input Parameter ◽  
Fringe Analysis ◽  
Development Partner ◽  
Input Parameters ◽  
Deviation Measurement ◽  
Facet Surface ◽  
Setup Variables

Sandia Optical Fringe Analysis Slope Tool (SOFAST) is a mirror facet characterization system based on fringe reflection technology that has been applied to dish and heliostat mirror facet development at Sandia National Laboratories and development partner sites. The tool provides a detailed map of mirror facet surface normals as compared to design and fitted surfaces. In addition, the surface fitting process provides insights into systematic facet slope characterization, such as focal lengths, tilts, and twist of the facet. In this paper, a preliminary analysis of the sensitivities of the facet characterization outputs to variations of SOFAST input parameters is presented. The results of the sensitivity analysis provided the basis for a linear uncertainty analysis which is also included here. Input parameters included hardware parameters and SOFAST setup variables. Output parameters included the fitted shape parameters (focal lengths and twist) and the residuals (typically called slope error). The study utilized empirical propagation of input parameter errors through facet characterization calculations to the output parameters, based on the measurement of an Advanced Dish Development System (ADDS) structural gore point-focus facet. Thus, this study is limited to the characterization of sensitivities of the SOFAST embodiment intended for dish facet characterization. With reasonably careful setup, SOFAST is demonstrated to provide facet focal length characterization within 0.5% of actual. Facet twist is accurate within ± 0.03 mrad/m. The local slope deviation measurement is accurate within ± 0.05 mrad, while the global slope residual is accurate within ± 0.005 mrad. All uncertainties are quoted with 95% confidence.

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