Accident Modification Factors for Traffic Engineering and ITS Improvements

Harkey, D L; Srinivasan, Raghavan; Baek, Jongdae; Eccles, Kimberly; Lefler, Nancy; Groß, Frank; Persaud, Bhagwant; Lyon, Craig; Hauer, Ezra; Bonneson, James A

doi:10.17226/13899

Cited by 9 publications

(7 citation statements)

References 17 publications

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“…The total crashes were reduced by 13% to 33% with an average reduction of 21%. NCHRP Report 617 assigned a medium-high level of predictive certainty to these estimates (Harkey, Council, & Gross, 2008). NCHRP Report 617 specifically states that the estimated safety effects are only applicable to freeways and not other types of roads (Harkey et al, 2008).…”

Section: Rumble Stripsmentioning

confidence: 99%

“…NCHRP Report 617 assigned a medium-high level of predictive certainty to these estimates (Harkey, Council, & Gross, 2008). NCHRP Report 617 specifically states that the estimated safety effects are only applicable to freeways and not other types of roads (Harkey et al, 2008). Specific to 2-lane rural roads, a 26.1% reduction was observed for SVROR collisions in a study of British Columbia roads (Sayed, DeLeur, & Pump, 2010).…”

Section: Rumble Stripsmentioning

confidence: 99%

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Case studies on estimating crash modification factors for treatment combinations with empirical investigation of dual rumble strip application in Ontario

Eskandar¹

2021

Preprint

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Crash modification factors (CMFs) are used to quantify the impact of safety treatments. These treatments are often used in combination and so the need for estimating CMFs for simultaneous applications arises. Applications of new heuristic methods in combining treatments showed mixed results, indicating a need for sound judgement in their usage. A case study for centreline and edgeline rumble strips on Ontario highways resulted in combined CMFs of 0.805, 0.79, 0.743, 0.799, and 0.689 for total, injury, PDO, single vehicle, and approach & sideswipe crash types, respectively. The estimates were comparable to the CMFs estimated in other research for actual dual rumble strip application. CMFs developed separately for tangent and curved segments showed that both rumble strip types are more effective on curved segments.

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Section: Rumble Stripsmentioning

confidence: 99%

Section: Rumble Stripsmentioning

confidence: 99%

Case studies on estimating crash modification factors for treatment combinations with empirical investigation of dual rumble strip application in Ontario

Eskandar¹

2021

Preprint

View full text Add to dashboard Cite

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“…Meanwhile, there were different methods to estimate CMFs, these methods were 1) the simple (naï ve) before and after study which compares number of crashes before the treatment and after treatment; 2) the before and after study with comparison group which was similar to the simple before and after study, however, it uses a comparison group of untreated sites to compensate for the external factors that could affect the change in the number of crashes; 3) the empirical Bayes (EB) before and after study which accounts for the regression to the mean issue; 4) the full Bayes before and after study which is similar to EB, however this method uses an expected crash frequency and its variance instead of using point estimate; and 5) the cross section method which was used to estimate CMFs when before and after data was missing for specific treatment (Juneyoung, 2015). Harkey et al (2008) estimated CMFs using cross-sectional studies. The authors found that cross-sectional studies can be used to estimate the safety effects of certain treatments on specific roadway types (e.g.…”

Section: Literature Reviewmentioning

confidence: 99%

“…The authors found that cross-sectional studies can be used to estimate the safety effects of certain treatments on specific roadway types (e.g. shoulder width of freeway) since it is difficult to isolate the effect of the treatment from the effects of other treatments applied at the same time using the before-after methods (Harkey et al, 2008). According to highway safety manual (HSM), the CMFs can be estimated by cross-sectional studies when the date of treatment installation was unknown.…”

Section: Literature Reviewmentioning

confidence: 99%

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Evaluating Safety of Type-A Weaving Sections Using Geometric and Traffic Operational Factors

Mallipaddi¹,

Anderson²

2020

IJSP

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The efficiency and safety of type-A freeway weaving sections in urban areas are constrained by recurrent bottlenecks. Limited space in freeway weaving sections cause traffic congestion and crashes during peak-hours. Various factors, including length of weaving section, continuity of lanes, and number of lanes will have significant effects on the level of service and safety performance of the weaving sections. Eight years (2010-2017) of crash data in the type-A weaving sections was used in this analysis. The objective of this study aims to evaluate geometric design factors and operational factors on total crashes and each of the four crash types: rear-end, sideswipe, angle, and single-vehicle in type-A weaving sections using traditional negative binomial approach and develop crash modification factors (CMFs) to improve safety in the type-A weaving section. The results revealed that on-ramp traffic per hour, off-ramp traffic per hour, non-weaving traffic per hour, weaving ratio, length of the weaving section, direction of the freeway, width of inside shoulder, and width of outside shoulder were influencing crashes in type-A weaving sections. Furthermore, the estimated crash modification factors (CMFs) result revealed that total crashes gradually decrease as inside shoulder width increases. This implies that widening inside shoulder width have positive effects on weaving section safety. In addition, ramp metering, and advisory warning signs could improve safety in type-A weaving sections.

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How overwhelming is the evidence in favor of Road Diets? A note on the cost-benefit methodology proposed by Noland et al. (2015)

Vine

2017

Case Studies on Transport Policy

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Writing in these pages, Noland and colleagues recently proposed a methodology for cost-benefit analysis of ‘Road Diets’ (re-design of the cross-section of a four-lane arterial). On the basis of the proposed procedures, the authors conclude that a Road Diet of an empirical case study (in New Brunswick, New Jersey, USA) would provide ‘overwhelming’ benefits. The study team has employed similarly unambiguous language in statements in other public fora. In this paper, I do not take a view of whether Road Diets are in general desirable or not (which will depend heavily on local context). Rather, I demonstrate here that the specification of benefits and costs in the proposed methodology is systematically biased (upwards in the case of ‘benefits’ and downwards in the case of ‘costs’). I also show that the authors mis-interpret public opinion regarding the proposed Road Diet; general public opinion cannot be known on the basis of the evidence that is presented to readers. Finally, it has been previously shown that transportation planners tend to, on average, systematically under-estimate costs and over-estimate benefits. While the authors’ motivations during the study at issue cannot be known, the systematic bias in specifying costs and benefits is consistent with Flyvbjerg’s ‘political-economic hypothesis’, in which it is theorized that planners strategically misrepresent costs and benefits in order to increase the likelihood of a politically-preferred project being advanced. Flyvbjerg suggests making independent peer reviews publicly available as part of a strategy to encourage accountability through transparency; this is the spirit in which the present paper is disseminated

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Accident Modification Factors for Traffic Engineering and ITS Improvements

Cited by 9 publications

References 17 publications

Case studies on estimating crash modification factors for treatment combinations with empirical investigation of dual rumble strip application in Ontario

Case studies on estimating crash modification factors for treatment combinations with empirical investigation of dual rumble strip application in Ontario

Evaluating Safety of Type-A Weaving Sections Using Geometric and Traffic Operational Factors

How overwhelming is the evidence in favor of Road Diets? A note on the cost-benefit methodology proposed by Noland et al. (2015)

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