Design Guidance for Channelized Right-Turn Lanes

Potts, Ingrid B; Harwood, D W; Bauer, Karin; Gilmore, D. K.; Hutton, Jessica M; Torbic, Darren J.; Ringert, John F; Daleiden, Andrew; Barlow, Janet M.

doi:10.17226/22238

“…However, it seems reasonable to expect that the CMF for installing a passing lane should not be single valued and should at least depend on the length of that lane. A later MRI study (Potts and Harwood, 2004) did find that crash frequency per mile per year within passing lane sections ranges from 12 to 24 percent lower than for conventional sections, with larger differences in crash rate at increasing levels of average daily traffic. However, a continuous function was not developed.…”

Section: Introductionmentioning

confidence: 93%

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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“…However, it seems reasonable to expect that the CMF for installing a passing lane should not be single valued and should at least depend on the length of that lane. A later MRI study (Potts and Harwood, 2004) did find that crash frequency per mile per year within passing lane sections ranges from 12 to 24 percent lower than for conventional sections, with larger differences in crash rate at increasing levels of average daily traffic. However, a continuous function was not developed.…”

Section: Introductionmentioning

confidence: 93%

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.

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“…Although several studies suggest that conflicts between motorists and vulnerable road users may occur, scientific research focusing on cyclists' and pedestrians' safety issues at CRTLs is limited. Several researchers hinted that drivers focus mainly on motorists driving on the road that they are about to merge into rather than on the potential presence of pedestrians and cyclists (Potts et al, 2011;Potts et al, 2013;Fitzpatrick et al, 2006;Polders et al, 2015). In these cases, drivers may see approaching vulnerable road users but are unable to detect them, succumbing to the "looked-but-failed-to-see" error (Hersland and Jørgensen, 2003).…”

Section: Figure 1 the Two Configurations For Accommodating Vulnerable Road Users On Crtls (Modified From Potts Et Al 2011)mentioning

confidence: 99%

Yielding behavior and traffic conflicts at cyclist crossing facilities on channelized right-turn lanes

Haperen

¹

,

Daniëls

²

,

Ceunynck

³

et al. 2018

Transportation Research Part F: Traffic Psychology and Behaviou

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Channelized right-turn lanes (CRTLs) improve traffic flow efficiency, enabling right-turning drivers to bypass traffic lights at signalised intersections (for right-hand drive countries). Many CRTLs provide crossing facilities for pedestrians and cyclists. Previous studies examining the safety performance of CRTLs indicate that they increase overall safety levels but hint that safety issues regarding vulnerable road users exist. This study investigated these issues through site-based observations of yielding behavior and evaluated the effect of the priority rule on cyclists' safety in two CRTL designs. Four locations in Belgium were selected for video observations: two where the priority rule favoured cyclists and two where motorists had priority.With regard to yielding, four types of crossing behavior were identified and defined. Independent of the priority rule, cyclists crossed the conflict zone first in most interactions without taking the initiative to cross first. Underlying reasons for motorists willingly giving away their right-of-way could not be determined, but possible courtesy or fear of inflicting injuries at vulnerable road users might be at hand. A safety evaluation was performed using two traffic conflict indicators (TTC min and the TA value). High correlations between the two indicators were found (r 2 > 0.83), but no conclusions about the safest priority rule for cyclists could be drawn. The results hinted, however, that locations with motorist priority and cyslists crossings from right to left (from the driver's point of view) yields the highest proportion of safety critical events.

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Design Guidance for Channelized Right-Turn Lanes

Cited by 6 publications

References 9 publications

Advancing the Methodology for Estimating the Effects of Safety Treatments

Advancing the Methodology for Estimating the Effects of Safety Treatments

Advancing the Methodology for Estimating the Effects of Safety Treatments

Yielding behavior and traffic conflicts at cyclist crossing facilities on channelized right-turn lanes

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