Digesting the safety effectiveness of cable barrier systems by numbers

Chimba, Deo; Ruhazwe, Evarist; Allen, Steve; Waters, Jim

doi:10.1016/j.tra.2016.11.013

Cited by 17 publications

(6 citation statements)

References 13 publications

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“…Overall, the cable barriers resulted in more single-vehicle crashes on wide medians; however, the severity of crashes were decreased in comparison with the before period. The similar results were found in the studies by Chimba et al [22] and Park et al [23]. Chimba et al [22] estimated averagely 82% and 76% less fatal and incapacitating injury crashes, respectively, after installing new cable barriers.…”

Section: Introductionsupporting

confidence: 86%

Modeling traffic barriers crash severity by considering the effect of traffic barrier dimensions

2019

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Traffic barriers are in widespread all around the USA as safety countermeasures for reducing the severity of runoff road crashes. The effect of traffic barriers' dimension had been ignored in past real-world crash studies due to the considerable cost and time needed for collecting field data. This paper presented two new analytical models to investigate the effect of different variables on the severity of crashes involving traffic barriers, and end treatments. For this reason, a field survey was conducted on over 1.3 million linear feet of traffic barriers (approximately 4,176 miles road) in Wyoming to measure traffic barriers' geometric features like height, length, offset, and slope rate. The collected data included 55% of all non-interstate roads of Wyoming. Based on results, the crashes involving box beam barriers were less severe than the crashes involved with W-beam or concrete barriers. The traffic barriers with a height between 28 and 31 in. were found safer than the traffic barriers shorter than 28 in., while there was no significant difference between the traffic barriers taller than 31 in. to those shorter than 28 in. in terms of crash severity. The end treatments located nearer to the traffic lane had lower crash severity. Keywords Crash severity Á Runoff road crashes Á Traffic barriers Á End treatments Á Traffic barrier dimensions Á Real-world crash analysis Á Wyoming

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Section: Introductionsupporting

confidence: 86%

Modeling traffic barriers crash severity by considering the effect of traffic barrier dimensions

2019

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“…Also, many of the previous attempts have examined how installation a particular type of barrier, such as cable median barrier, affects the frequency and severity of crashes. As a case in point, cable median barriers have been generally found to reduce severe crashes (Alluri et al, 2012, Chimba et al, 2017, while they may increase the odds of property damage only and less severe crashes.…”

Section: Median Width and Safetymentioning

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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Section: Median Width and Safetymentioning

confidence: 99%