A Comparative Analysis on Performance of Severe Crash Prediction Methods

Avelar, Raul; Dixon, Karen; Ashraf, Sruthi

doi:10.1177/0361198118794052

“…The results suggested that the SDF approach outperforms the approach of developing separate models for each injury severity category. More recently, Avelar et al, (2018) conducted a comparative analysis on performance of severe crash prediction alternatives to illustrate the strengths and weaknesses of each method. A comparison was made and it was found that the performance of direct estimation of severe crashes was similar to that of using the SDF approach.…”

Section: Predicting Crash Frequency By Severitymentioning

confidence: 99%

“…Examples of the development and application of the SDF approach includeShea et al (2015), Dixon et al (2015 andAvelar et al (2018). Other notable examples are cited in Chapter 3.…”

mentioning

confidence: 99%

Advancing the Methodology for Estimating the Effects of Safety Treatments

Anarkooli¹

2023

Preprint

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The Highway Safety Manual uses safety performance functions (SPFs) and crash modification factors (CMFs) to quantify the safety effects of a roadway design and operational changes. A number of substantial methodological issues in SPF and CMF estimation exist that have not yet been completely addressed. Notably, although applicability of SPFs and CMFs may significantly vary by crash severity, only limited consideration is given to severity distribution. Moreover, when developing crash modification functions (CMFunctions), most of the current state-of-the-art studies only rely on the functional forms that may not address the non-linear effects of roadway attributes on safety. In addition, while many studies advocate using traffic conflicts as surrogate measures of safety to address some issues in CMF estimation, most of the current measures do not sufficiently take into account the severity of conflicts. The thesis is based on an amalgamation of four research papers that separately delve into these topics in Chapters 3 to 6. Chapter 3 develops and compares alternative approaches for predicting number of crashes for each severity level. The applicability of a two-stage SDF (severity distribution function) modeling approach is the main focus of this chapter. Chapter 4 applies Bayesian Markov Chain Monte Carlo (MCMC) simulation to investigate the functional forms used to derive CMFunctions in cross- sectional regression models. This chapter mainly focuses on the methodology and uses freeway median width as a case study. Chapter 5 aims to demonstrate the versatility of the approach by applying that to passing lanes on two-lane roads. The results of these two applications highlight the importance of using the functional forms that can capture non-linear effects of road attributes for CMF estimation in cross- sectional models, while providing robust CMFs for practical applications. Chapter 6 investigates a novel traffic technique using the data obtained from video observations at signalized intersections. The measures of post encroachment times and corresponding conflicting vehicle speeds are integrated to define a risk score which classifies conflicts into three severity levels. The results show strong relationships between the classified conflicts and both total and fatal/injury crashes and conform the promise of the approach for estimating CMFs where there are insufficient crash data for directly estimating them.

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“…The results suggested that the SDF approach outperforms the approach of developing separate models for each injury severity category. More recently, Avelar et al, (2018) conducted a comparative analysis on performance of severe crash prediction alternatives to illustrate the strengths and weaknesses of each method. A comparison was made and it was found that the performance of direct estimation of severe crashes was similar to that of using the SDF approach.…”

Section: Predicting Crash Frequency By Severitymentioning

confidence: 99%

“…Examples of the development and application of the SDF approach includeShea et al (2015), Dixon et al (2015 andAvelar et al (2018). Other notable examples are cited in Chapter 3.…”

mentioning

confidence: 99%

Advancing the Methodology for Estimating the Effects of Safety Treatments

Anarkooli¹

2023

Preprint

0

View full text Add to dashboard Cite

The Highway Safety Manual uses safety performance functions (SPFs) and crash modification factors (CMFs) to quantify the safety effects of a roadway design and operational changes. A number of substantial methodological issues in SPF and CMF estimation exist that have not yet been completely addressed. Notably, although applicability of SPFs and CMFs may significantly vary by crash severity, only limited consideration is given to severity distribution. Moreover, when developing crash modification functions (CMFunctions), most of the current state-of-the-art studies only rely on the functional forms that may not address the non-linear effects of roadway attributes on safety. In addition, while many studies advocate using traffic conflicts as surrogate measures of safety to address some issues in CMF estimation, most of the current measures do not sufficiently take into account the severity of conflicts. The thesis is based on an amalgamation of four research papers that separately delve into these topics in Chapters 3 to 6. Chapter 3 develops and compares alternative approaches for predicting number of crashes for each severity level. The applicability of a two-stage SDF (severity distribution function) modeling approach is the main focus of this chapter. Chapter 4 applies Bayesian Markov Chain Monte Carlo (MCMC) simulation to investigate the functional forms used to derive CMFunctions in cross- sectional regression models. This chapter mainly focuses on the methodology and uses freeway median width as a case study. Chapter 5 aims to demonstrate the versatility of the approach by applying that to passing lanes on two-lane roads. The results of these two applications highlight the importance of using the functional forms that can capture non-linear effects of road attributes for CMF estimation in cross- sectional models, while providing robust CMFs for practical applications. Chapter 6 investigates a novel traffic technique using the data obtained from video observations at signalized intersections. The measures of post encroachment times and corresponding conflicting vehicle speeds are integrated to define a risk score which classifies conflicts into three severity levels. The results show strong relationships between the classified conflicts and both total and fatal/injury crashes and conform the promise of the approach for estimating CMFs where there are insufficient crash data for directly estimating them.

show abstract