National-Level Safety Evaluation of Diverging Diamond Interchanges

2019 ◽  
Vol 2673 (7) ◽  
pp. 696-708
Author(s):  
Timothy S. Nye ◽  
Christopher M. Cunningham ◽  
Elizabeth Byrom
Keyword(s):  
Empirical Bayes ◽  
Comparison Group ◽  
National Level ◽  
Group Analysis ◽  
Safety Evaluation ◽  
The United States ◽  
Group Method ◽  
Regression To The Mean ◽  
Naive Method ◽  
Diamond Interchanges

A national-level safety evaluation of Diverging Diamond Interchanges (DDIs) in the United States was completed. This study aimed to update previous evaluations and to expand the treatment group size of previous studies to provide a more robust and reliable safety assessment of DDI deployments. For this particular treatment, it was determined that, of the observational before-and-after evaluation methodologies, the comparison group approach yields the best evaluation results. The naïve method can be influenced by outside factors that cannot be accounted for (weather, crash reporting tendencies, etc.). The empirical Bayes method is unnecessary as DDIs are installed for operational benefits, meaning that risk of selection bias and regression-to-the-mean is minimal. This study recommends a total crashes crash modification factor (CMF) of 0.633 based on the comparison group analysis of 26 DDIs in 11 states. The comparison group method was also applied to a variety of crash variables for this study. Angle, rear-end, and sideswipe crashes were found to have CMFs of 0.441, 0.549, and 1.139, respectively. Fatal-and-injury crashes provided a CMF of 0.461. Daytime and nighttime crashes provided CMFs of 0.648 and 0.638, respectively.

Long-Term Effect of Universal Helmet Law Changes on Motorcyclist Fatal Crashes: Comparison Group and Empirical Bayes Approaches

2017 ◽  
Vol 2637 (1) ◽  
pp. 27-37 ◽  
Author(s):  
Jaeyoung Lee ◽  
Mohamed Abdel-Aty ◽  
Jung-Han Wang ◽  
Chanyoung Lee
Keyword(s):  
Empirical Bayes ◽  
Brain Injuries ◽  
Comparison Group ◽  
The United States ◽  
Regression To The Mean ◽  
Fatal Crashes ◽  
Before And After ◽  
The Law ◽  
1960S And 1970S

A motorcyclist helmet is considered important safety equipment because it prevents or minimizes head and brain injuries, which are often fatal. Hence, in the 1960s and 1970s, most of the states in the United States enacted the universal helmet law (UHL) requiring all motorcyclists to wear helmets. Many researchers have examined the effect of the helmet law changes by using before-and-after studies and found that repealing the law had a negative effect on motorcyclists. In this study, the authors have attempted to explore the long-term impacts of repeal and reinstatement of the UHL by using 13 to 16 years of data. A before-and-after study with a comparison group and empirical Bayes methods was adopted to account for the passage of time and its effect on other factors such as exposure, maturation, trend, and regression-to-the-mean bias. A range of safety performance functions was developed on the basis of counties and parishes, and the expected fatal motorcycle crashes were calculated. The results showed that the UHL repeal still had significant effects on motorcycle fatal crash counts even 7 to 12 years after the repeal of the law. The crash modification factors showed that the UHL repeal increased the number of motorcycle fatal crashes by 15% to 41%, whereas reinstatement of the UHL decreased it by 21% to 27%. It is expected that the results from this study could be helpful for state policy makers to clearly understand the effects of the UHL on reducing motorcycle fatal crashes.

Safety Evaluation of Pedestrian Countdown Signals: Definitive Results from Two Cities in the United States

2021 ◽  
pp. 036119812110634
Author(s):  
Raghavan Srinivasan ◽  
Bo Lan ◽  
Daniel Carter ◽  
Sarah Smith ◽  
Bhagwant Persaud ◽  
...  
Keyword(s):  
Confidence Level ◽  
Empirical Bayes ◽  
Safety Evaluation ◽  
The United States ◽  
Cost Ratio ◽  
Regression To The Mean ◽  
Benefit Cost Ratio ◽  
Inadequate Sample Size ◽  
Pedestrian Crashes ◽  
Using Data

The pedestrian countdown signals (PCS) treatment involves the display of a numerical countdown that shows how many seconds are left in the flashing DON’T WALK interval. Although many studies have attempted to evaluate the safety of PCS, the results have been inconsistent for many reasons, including inadequate sample size and the inability to control for possible bias from regression to the mean and from exposure. This study performed a before-after empirical Bayes analysis using data from 115 treated intersections in Charlotte, North Carolina and 218 treated intersections in Philadelphia, Pennsylvania to evaluate the safety effects of PCS. The evaluation also included 136 reference intersections in Charlotte, and 597 reference intersections in Philadelphia. Following the implementation of PCS, total crashes decreased by approximately 8% and rear-end crashes decreased by approximately 12%, and these reductions were statistically significant at the 95% confidence level. Pedestrian crashes decreased by about 9% and this reduction was statistically significant at the 90% confidence level. Economic analysis revealed a benefit-cost ratio of 23 with a low of 13 and a high of 32.

Development of Crash Reduction Factors: Methods, Problems, and Research Needs

2003 ◽  
Vol 1840 (1) ◽  
pp. 50-56 ◽  
Author(s):  
Joan Shen ◽  
Albert Gan
Keyword(s):  
Empirical Bayes ◽  
Group Method ◽  
Research Needs ◽  
Regression To The Mean ◽  
Before And After ◽  
Safety Studies ◽  
Development Methods ◽  
Crash Reduction ◽  
Before And After Study ◽  
Reduction Factors

Crash reduction factors (CRFs) are used in highway safety studies to predict safety benefits due to reduced numbers of crashes. NCHRP Report 162 identified the need for the development of a national comprehensive set of CRFs for each state to evaluate safety improvements. However, this need has not been met. As a result, many states have developed their own CRFs or have adopted CRFs from other states. A synthesis of the CRF development methods, the associated problems, and the research needs are provided. The emphasis is placed on the before-and-after study method because it has been, and still is, the method of choice for CRF development. Three before-and-after study methods were introduced and reviewed: ( a) the simple before-and-after method, ( b) the before-and-after study with comparison group method, and ( c) the before-and-after study with the empirical Bayes method. The problems associated with the simple before-and-after studies, including regression to the mean, crash migration, maturation, and external causal factor, are discussed. Several research needs related to crash migration and general CRF development are also identified. The information presented in the synthesis will be useful to states that plan to develop or update their CRFs.

Safety Evaluation of Seven of the Earliest Diverging Diamond Interchanges Installed in the United States

2016 ◽  
Vol 2583 (1) ◽  
pp. 25-33 ◽  
Author(s):  
Joseph E. Hummer ◽  
Christopher M. Cunningham ◽  
Raghavan Srinivasan ◽  
Shannon Warchol ◽  
Boris Claros ◽  
...  
Keyword(s):  
United States ◽  
Safety Evaluation ◽  
The United States ◽  
Diamond Interchanges

Traffic Conflict–Based Before–After Study with Use of Comparison Groups and the Empirical Bayes Method

2017 ◽  
Vol 2659 (1) ◽  
pp. 15-24 ◽  
Author(s):  
Passant Reyad ◽  
Emanuele Sacchi ◽  
Shewkar Ibrahim ◽  
Tarek Sayed
Keyword(s):  
Road Safety ◽  
Empirical Bayes ◽  
Comparison Group ◽  
Treatment Effectiveness ◽  
Video Data ◽  
Safety Performance ◽  
Group Method ◽  
Safety Level ◽  
Before And After ◽  
Traffic Conflict

Road safety evaluations mainly rely on the analysis of crash data that are challenged by well-recognized availability and quality issues. The statistical models used to predict the safety level of road sites—that is, safety performance functions—have recently been successfully developed with the use of traffic conflict observations instead of crashes. As such, it is possible to adopt and transfer the statistical techniques used in crash-based road safety analysis to conflict-based analysis. The use of statistically rigorous techniques in crash-based before-and-after (BA) studies is essential for evaluation of the effectiveness of road safety countermeasures. In particular, the use of Bayesian methods, such as the empirical Bayes (EB) technique, is vital to control for confounding factors that can operate simultaneously with the countermeasure and may affect road safety performance. The main objective of this paper was to estimate the treatment effectiveness of two traffic signal (visibility) improvement projects in the city of Edmonton, Alberta, Canada, with a conflict-based BA study using the comparison group and the EB methods. More than 300 h of video data with traffic conflict observations was automatically collected and analyzed by computer vision techniques for two treatment intersections and two control (untreated) intersections before and after the signal improvement projects. The results of the comparison group method showed a statistically significant 24% reduction in the average number of rear-end conflicts per hour, whereas the EB method showed a statistically significant 24.5% reduction in the average number of total conflicts per hour.

Systematic Safety Evaluation of Diverging Diamond Interchanges Based on Nationwide Implementation Data

2021 ◽  
pp. 036119812110049
Author(s):  
Ahmed Abdelrahman ◽  
Mohamed Abdel-Aty ◽  
Jinghui Yuan ◽  
Ma’en M. A. Al-Omari
Keyword(s):  
Empirical Bayes ◽  
Safety Evaluation ◽  
Safety Performance ◽  
Cross Sectional ◽  
Crash Frequency ◽  
Left Turn ◽  
Crash Modification Factors ◽  
Diamond Interchanges ◽  
Implementation Data ◽  
Sectional Analysis

Diverging diamond interchanges (DDIs) are designed as an alternative to the conventional diamond interchanges to enhance operational and safety performance. As the popularity of the DDI is increasing and more DDIs are being constructed and proposed, the need has arisen to measure the actual safety benefits of DDIs as compared with the traditional diamond interchanges. This study evaluates the safety of DDIs using three methods: before–after study with comparison group, Empirical Bayes before–after method, and cross-sectional analysis. This study collected a nationwide sample of 80 DDIs in 24 states. The estimated crash modification factors indicated that converting conventional diamond interchange to DDIs could significantly decrease the total, fatal-and-injury, rear-end, and angle/left-turn crashes by 14%, 44%, 11%, and 55%, respectively. Moreover, the developed safety performance functions implied that a longer distance between crossovers/ramp terminals and a lower speed limit on freeway exit ramps are significantly associated with lower crash frequency at diamond interchanges. This study contributes to the existing literature using a relatively large representative sample size, which provides more reliable evaluation results. In addition, this study also explored the effects of different traffic and geometric characteristics on the safety performance of DDIs.

Multijurisdictional Safety Evaluation of Red Light Cameras

2005 ◽  
Vol 1922 (1) ◽  
pp. 29-37 ◽  
Author(s):  
Bhagwant Persaud ◽  
Forrest M. Council ◽  
Craig Lyon ◽  
Kimberly Eccles ◽  
Mike Griffith
Keyword(s):  
United States ◽  
Empirical Bayes ◽  
Red Light ◽  
Spillover Effect ◽  
Safety Evaluation ◽  
Economic Cost ◽  
The United States ◽  
Companion Paper ◽  
Background Information ◽  
Outcome Variable

The use of red light camera (RLC) systems has risen dramatically in the United States in recent years. The size of the problem, the promise shown by RLC systems in other countries, and the paucity of definitive U.S. studies have motivated a multijurisdictional U.S. study. The fundamental objective of this study, which was sponsored by FHWA, was to determine the effectiveness of the RLC systems in reducing crashes at monitored intersections as well as jurisdictionwide. Phase I involved the development of a detailed experimental design that included collection of background information, establishment of study goals, selection of potential study jurisdictions, and specification of statistical methodology. In Phase 2, an empirical Bayes before-and-after study used data from seven jurisdictions across the United States, with a total of 132 treatment sites. Effects detected were consistent in direction with those found in many previous studies—a decrease in right-angle crashes and an increase in rear-end crashes—although both effects are somewhat lower than those reported in many sources. The extent to which the increase in rear-end crashes negates the benefits for right-angle crashes is unclear and points to the need for an examination of the economic cost of crashes, which is the subject of a companion paper, to aggregate the effects on rear-end, right-angle, and other crash costs. That second paper seeks to isolate all factors that would favor the installation of RLC systems by using the aggregate economic benefit as the outcome variable. There were weak indications of a spillover effect, which point to a need for a more definitive, perhaps prospective, study of this issue.

Safety Evaluation of Roundabouts in Georgia

2019 ◽  
Vol 2673 (7) ◽  
pp. 641-651
Author(s):  
Franklin E. Gbologah ◽  
Angshuman Guin ◽  
Michael O. Rodgers
Keyword(s):  
Empirical Bayes ◽  
Safety Evaluation ◽  
The United States ◽  
Small Sample ◽  
Data Availability ◽  
Evaluation Procedure ◽  
Crash Frequency ◽  
Fatal Crashes ◽  
Bayes Analysis ◽  
Departments Of Transportation

U.S. roundabout growth has been significant in recent years and many published studies have documented significant safety benefits of roundabouts. However, the safety benefits for a roundabout may vary from region to region depending on many local factors. Therefore, transportation agencies can make more informed implementation decisions with local safety evaluations rather than published national findings. However, roundabouts are relatively new in the United States and most departments of transportation, including Georgia, are often hindered by the data availability requirements of the state-of-the-art empirical Bayes analysis evaluation procedure. This current study provides a safety evaluation of 23 Georgia roundabouts. It adopts a time-dependent form of the Highway Safety Manual predictive (empirical Bayes) method to estimate potential crash reductions across all crashes and all injury/fatal crashes. The method extends the empirical Bayes procedure towards a full Bayesian analysis. The findings indicate a 37–48% reduction in average crash frequency for all crashes and a 51–60% reduction in average crash frequency for injury/fatal crashes at four-leg roundabouts that were converted from stop-controlled and conventional intersections. In addition, when analyzed as a group, three-leg and four-leg roundabouts converted from stop-controlled and conventional intersections collectively experienced 56% reduction in average crash frequency for all crashes and 69% reduction in injury/fatal crashes. The study did not consider five-leg roundabouts because of small sample size and concerns about the form of the safety performance function. The adopted methodology offers departments of transportation with data availability challenges an alternative evaluation framework that retains the positive attributes of empirical Bayes analysis.

Applicability of management guidelines for surfing resources in California

Shore & Beach ◽  
2020 ◽  
pp. 53-64
Author(s):  
Edward Atkin ◽  
Dan Reineman ◽  
Jesse Reiblich ◽  
David Revell
Keyword(s):  
New Zealand ◽  
National Level ◽  
State Level ◽  
The United States ◽  
Management Guidelines ◽  
For Profit ◽  
Aotearoa New Zealand ◽  
Coastal Marine ◽  
Management Measures ◽  
Legal Frameworks

Surf breaks are finite, valuable, and vulnerable natural resources, that not only influence community and cultural identities, but are a source of revenue and provide a range of health benefits. Despite these values, surf breaks largely lack recognition as coastal resources and therefore the associated management measures required to maintain them. Some countries, especially those endowed with high-quality surf breaks and where the sport of surfing is accepted as mainstream, have recognized the value of surfing resources and have specific policies for their conservation. In Aotearoa New Zealand surf breaks are included within national environmental policy. Aotearoa New Zealand has recently produced Management Guidelines for Surfing Resources (MGSR), which were developed in conjunction with universities, regional authorities, not-for-profit entities, and government agencies. The MGSR provide recommendations for both consenting authorities and those wishing to undertake activities in the coastal marine area, as well as tools and techniques to aid in the management of surfing resources. While the MGSR are firmly aligned with Aotearoa New Zealand’s cultural and legal frameworks, much of their content is applicable to surf breaks worldwide. In the United States, there are several national-level and state-level statutes that are generally relevant to various aspects of surfing resources, but there is no law or policy that directly addresses them. This paper describes the MGSR, considers California’s existing governance frameworks, and examines the potential benefits of adapting and expanding the MGSR in this state.

Patient Autonomy, Capacity, and Consent

2020 ◽  
Author(s):  
Mary Donnelly ◽  
Jessica Berg
Keyword(s):  
United States ◽  
National Level ◽  
The United States ◽  
Legal Framework ◽  
National Standard ◽  
Legal Principles ◽  
Key Issues ◽  
Human Rights Norms ◽  
Law And Legislation

This chapter explores a number of key issues: the role of competence and capacity, advance directives, and decisions made for others. It analyses the ways these are treated in the United States and in selected European jurisdictions. National-level capacity legislation and human rights norms play a central role in Europe, which means that healthcare decisions in situations of impaired capacity operate in accordance with a national standard. In the United States, the legal framework is more state-based (rather than federal), and the courts have played a significant role, with both common law and legislation varying considerably across jurisdictions. Despite these differences, this chapter identifies some similar legal principles which have developed.

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