scholarly journals Analysis of passing sight distance using first-order reliability method

2021 ◽  
Author(s):  
Said Easa
Keyword(s):  
Safety Margin ◽  
Field Studies ◽  
Vehicle Speed ◽  
Second Moment ◽  
First Order ◽  
State Highway ◽  
Sight Distance ◽  
Design Variables ◽  
Reliability Method ◽  
First Order Second Moment

Current passing sight distance requirements for two lane highways by the American Association of State Highway and Transportation Officials are based on field studies conducted between 1938 and 1941 which use deterministic values for its design variables such as passing sight distance, speed of the passing vehicle, speed differential between the passed and passing vehicle etc. This report presents three methods to analyze reliability and serves as an extension to the revised model presented by Yasser Hassan, Said Easa and A.O.Abd El Halim whose model sought to improve older models by equally considering both observed passing behaviours of drivers and passing maneuvers that are consistent with two lane highways. Analysis of passing sight distance using first order second moment reliability method, advanced first order second moment and the ellipsoid approach to measure the probability of failure of the passing sight distance design, rely solely on the mean and variance (moments) of each randomly distributed variable in contrast to methods that rely only on deterministic values. Results show the advanced first order second moment and the ellipsoid approach provided more accurate results than first order second moment method which in turn provide a greater safety margin with the later also proving to be a much more robust and efficient method of performing a reliability

scholarly journals Analysis of passing sight distance using first-order reliability method

2021 ◽  
Author(s):  
Said Easa
Keyword(s):  
Safety Margin ◽  
Field Studies ◽  
Vehicle Speed ◽  
Second Moment ◽  
First Order ◽  
State Highway ◽  
Sight Distance ◽  
Design Variables ◽  
Reliability Method ◽  
First Order Second Moment

Current passing sight distance requirements for two lane highways by the American Association of State Highway and Transportation Officials are based on field studies conducted between 1938 and 1941 which use deterministic values for its design variables such as passing sight distance, speed of the passing vehicle, speed differential between the passed and passing vehicle etc. This report presents three methods to analyze reliability and serves as an extension to the revised model presented by Yasser Hassan, Said Easa and A.O.Abd El Halim whose model sought to improve older models by equally considering both observed passing behaviours of drivers and passing maneuvers that are consistent with two lane highways. Analysis of passing sight distance using first order second moment reliability method, advanced first order second moment and the ellipsoid approach to measure the probability of failure of the passing sight distance design, rely solely on the mean and variance (moments) of each randomly distributed variable in contrast to methods that rely only on deterministic values. Results show the advanced first order second moment and the ellipsoid approach provided more accurate results than first order second moment method which in turn provide a greater safety margin with the later also proving to be a much more robust and efficient method of performing a reliability

scholarly journals Reliability Analysis Approach For Intersection Sight Distance Of A Symmetrical Single-Lane Roundabout

2021 ◽  
Author(s):  
Paria Sarshar
Keyword(s):  
Reliability Analysis ◽  
Safety Margin ◽  
Random Variables ◽  
Analysis Approach ◽  
Deterministic Models ◽  
Second Moment ◽  
First Order ◽  
Sight Distance ◽  
Design Variables ◽  
First Order Second Moment

The current intersection sight distance values on a roundabout provided by ASSHTO and other worldwide guidelines are based on deterministic methods considering only single variables as the design inputs. However, most of the input design variables such as entering speed and the deceleration rate are random variables which are stochastic in nature. Therefore, this study proposes a reliability analysis approach to add uncertainty to the current deterministic models. Two different reliability approaches; the first order second moment and advanced first order second moment are presented in this paper. These approaches rely on the normal distribution of the random variables using the mean, variance and the covariance of the probability distribution of each variable rather than the single deterministic values. Results show that the AFOSM reliability methodology provides a more conservative outcome which ensures a greater safety margin comparing to FOSM which appears to be a more efficient and robust methodology.

scholarly journals Reliability analysis of truck escape ramp design

2021 ◽  
Author(s):  
Kaitlyn Ann Greto
Keyword(s):  
Reliability Analysis ◽  
Safety Margin ◽  
Rolling Resistance ◽  
Second Moment ◽  
First Order ◽  
Stopping Distance ◽  
Design Variables ◽  
Reliability Method ◽  
First Order Second Moment ◽  
Design Speed

The truck escape ramp design presented by the Transportation Association of Canada is based on deterministic values of the design variables which include the required stopping distance, design speed, rolling resistance, and grade. Currently, a reliability analysis of the design of truck escape ramps does not exist. This report presents two methods used to analyze the reliability of truck escape ramp design; the first order second moment reliability method and the advanced first order second moment reliability method. These methods do not rely on deterministic values rather the mean and variance (moments) of each random variable’s probability distribution. Each reliability method was used to analyze truck escape ramps with one grade and two grades, for a total of four cases. The results of each case are provided and discussed along with an application to two existing truck escape ramps. The results show that the advanced first order second moment reliability method ensures more accurate results as well as a larger safety margin in comparison to the first order second moment method due to the nature of the methodology itself which considers design points.

scholarly journals Reliability Analysis Approach For Intersection Sight Distance Of A Symmetrical Single-Lane Roundabout

2021 ◽  
Author(s):  
Paria Sarshar
Keyword(s):  
Reliability Analysis ◽  
Safety Margin ◽  
Random Variables ◽  
Analysis Approach ◽  
Deterministic Models ◽  
Second Moment ◽  
First Order ◽  
Sight Distance ◽  
Design Variables ◽  
First Order Second Moment

The current intersection sight distance values on a roundabout provided by ASSHTO and other worldwide guidelines are based on deterministic methods considering only single variables as the design inputs. However, most of the input design variables such as entering speed and the deceleration rate are random variables which are stochastic in nature. Therefore, this study proposes a reliability analysis approach to add uncertainty to the current deterministic models. Two different reliability approaches; the first order second moment and advanced first order second moment are presented in this paper. These approaches rely on the normal distribution of the random variables using the mean, variance and the covariance of the probability distribution of each variable rather than the single deterministic values. Results show that the AFOSM reliability methodology provides a more conservative outcome which ensures a greater safety margin comparing to FOSM which appears to be a more efficient and robust methodology.

scholarly journals Reliability of stopping and decision sight distance at roundabouts

2021 ◽  
Author(s):  
Jafar Faizi
Keyword(s):  
Probabilistic Method ◽  
Design Parameters ◽  
Second Moment ◽  
First Order ◽  
State Highway ◽  
Sight Distance ◽  
Design Variables ◽  
First Order Second Moment ◽  
Stopping Sight Distance ◽  
Lateral Clearance

The existing Stopping Sight Distance (SSD) and Decision Sight Distance (DSD) design methods for roundabouts are deterministic. This means that all of the design variables are predetermined, fixed values. This study presents a probabilistic method for the determination of SSD and DSD at roundabouts based on the equation recommended by the American Association of State Highway and Transportation Officials (AASHTO 2011). The reliability-based method considers all design parameters as random variables. Three types of SSD (SSD for approaches, SSD along the circulatory lane, and SSD for exiting vehicles to the pedestrian crosswalk) were considered in this study. DSD was considered for roundabout approaches. The First-Order Second-Moment and Advanced First-Order Second-Moment methods were used to model SSD and DSD. Once the required SSD and DSD were determined, the lateral clearance requirements at every point of the roundabout were calculated.

scholarly journals Reliability analysis of truck escape ramp design

2021 ◽  
Author(s):  
Kaitlyn Ann Greto
Keyword(s):  
Reliability Analysis ◽  
Safety Margin ◽  
Rolling Resistance ◽  
Second Moment ◽  
First Order ◽  
Stopping Distance ◽  
Design Variables ◽  
Reliability Method ◽  
First Order Second Moment ◽  
Design Speed

The truck escape ramp design presented by the Transportation Association of Canada is based on deterministic values of the design variables which include the required stopping distance, design speed, rolling resistance, and grade. Currently, a reliability analysis of the design of truck escape ramps does not exist. This report presents two methods used to analyze the reliability of truck escape ramp design; the first order second moment reliability method and the advanced first order second moment reliability method. These methods do not rely on deterministic values rather the mean and variance (moments) of each random variable’s probability distribution. Each reliability method was used to analyze truck escape ramps with one grade and two grades, for a total of four cases. The results of each case are provided and discussed along with an application to two existing truck escape ramps. The results show that the advanced first order second moment reliability method ensures more accurate results as well as a larger safety margin in comparison to the first order second moment method due to the nature of the methodology itself which considers design points.

scholarly journals Reliability of stopping and decision sight distance at roundabouts

2021 ◽  
Author(s):  
Jafar Faizi
Keyword(s):  
Probabilistic Method ◽  
Design Parameters ◽  
Second Moment ◽  
First Order ◽  
State Highway ◽  
Sight Distance ◽  
Design Variables ◽  
First Order Second Moment ◽  
Stopping Sight Distance ◽  
Lateral Clearance

The existing Stopping Sight Distance (SSD) and Decision Sight Distance (DSD) design methods for roundabouts are deterministic. This means that all of the design variables are predetermined, fixed values. This study presents a probabilistic method for the determination of SSD and DSD at roundabouts based on the equation recommended by the American Association of State Highway and Transportation Officials (AASHTO 2011). The reliability-based method considers all design parameters as random variables. Three types of SSD (SSD for approaches, SSD along the circulatory lane, and SSD for exiting vehicles to the pedestrian crosswalk) were considered in this study. DSD was considered for roundabout approaches. The First-Order Second-Moment and Advanced First-Order Second-Moment methods were used to model SSD and DSD. Once the required SSD and DSD were determined, the lateral clearance requirements at every point of the roundabout were calculated.

scholarly journals Reliability analysis of pedestrian crossing sight distance

2021 ◽  
Author(s):  
Sadia Karim
Keyword(s):  
Reaction Time ◽  
Reliability Analysis ◽  
Coefficient Of Variation ◽  
Safety Margin ◽  
Vehicle Speed ◽  
Major Road ◽  
First Order ◽  
Sight Distance ◽  
First Order Second Moment ◽  
Pedestrian Crossing

The main objective of this study was to calculate the required sight distance corresponding to the various probabilities of failure by considering two methods of reliability analysis. This paper presents a probabilistic approach based on such random variables as major road vehicle speed, walking speed, pedestrian observation-reaction time, the length of the crossing unit, pedestrian setback from the nearest curb of the major road. A safety margin is defined as the difference between available and required sight distances. By using the first-order second moment (FOSM) method, relationships for the mean and standard deviation of the safety margin were developed. The advance first-order second-moment (AFOSM) was also used to find the supplied sight distance corresponding to reliability index. Comparison of two methods was done. Obtained results from the two methods were almost similar to a low coefficient of variation. Different design graphs were developed to calculate the required sight distance at a different coefficient of variation corresponding to the probability of failure and different vehicle design. Sensitivity analysis was performed to obtain the most sensitive variable to the pedestrian crossing sight distance. It was found that vehicle speed is more sensitive to required sight distance and perception-reaction time has least effect on supplied (required) sight distance. Application of these methods is presented with two examples. This probabilistic method is valuable in designing pedestrian crossing sight distance for any preferred reliability level.

scholarly journals Reliability analysis of pedestrian crossing sight distance

2021 ◽  
Author(s):  
Sadia Karim
Keyword(s):  
Reaction Time ◽  
Reliability Analysis ◽  
Coefficient Of Variation ◽  
Safety Margin ◽  
Vehicle Speed ◽  
Major Road ◽  
First Order ◽  
Sight Distance ◽  
First Order Second Moment ◽  
Pedestrian Crossing

The main objective of this study was to calculate the required sight distance corresponding to the various probabilities of failure by considering two methods of reliability analysis. This paper presents a probabilistic approach based on such random variables as major road vehicle speed, walking speed, pedestrian observation-reaction time, the length of the crossing unit, pedestrian setback from the nearest curb of the major road. A safety margin is defined as the difference between available and required sight distances. By using the first-order second moment (FOSM) method, relationships for the mean and standard deviation of the safety margin were developed. The advance first-order second-moment (AFOSM) was also used to find the supplied sight distance corresponding to reliability index. Comparison of two methods was done. Obtained results from the two methods were almost similar to a low coefficient of variation. Different design graphs were developed to calculate the required sight distance at a different coefficient of variation corresponding to the probability of failure and different vehicle design. Sensitivity analysis was performed to obtain the most sensitive variable to the pedestrian crossing sight distance. It was found that vehicle speed is more sensitive to required sight distance and perception-reaction time has least effect on supplied (required) sight distance. Application of these methods is presented with two examples. This probabilistic method is valuable in designing pedestrian crossing sight distance for any preferred reliability level.

Reliability analysis of a structural element based on the Advanced First-Order-Second-Moment Method.

1985 ◽  
Vol 51 (472) ◽  
pp. 2811-2816
Author(s):  
Yoshisada MUROTSU ◽  
Masaaki YONEZAWA ◽  
Hiroo OKADA ◽  
Satoshi MATSUZAKI ◽  
Toshiki MATSUMOTO
Keyword(s):  
Reliability Analysis ◽  
Moment Method ◽  
Structural Element ◽  
Second Moment ◽  
First Order ◽  
First Order Second Moment ◽  
Second Moment Method
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