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.

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.

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.

Level of Safety on Two-Lane Undivided Rural Highways

2012 ◽  
Vol 253-255 ◽  
pp. 1705-1710 ◽  
Author(s):  
Giuseppe Guido ◽  
Alessandro Vitale ◽  
Vincenzo Gallelli ◽  
Giuseppe Figliomeni
Keyword(s):  
Safety Performance ◽  
Accident Risk ◽  
Performance Study ◽  
Safety Level ◽  
Rural Highways ◽  
Roadway Safety ◽  
Traffic Stream ◽  
Traffic Conflict ◽  
Traffic Level ◽  
Rural Highway

Due to the great increase of congestion levels on transportation infrastructures researchers and practitioners have focused on the study of safety performance on road network to identify unsafe locations and assess the effectiveness of different countermeasures introduced at a given site to reduce unacceptable accident risk. Safety performance measures represent an useful tool for evaluating road safety conditions on the basis of objective parameters deducible from the vehicle kinematics. The focus of the present paper is on the assessment of the safety level on two-lane rural highway with a particular attention on rear-end interactions among different pairs of vehicles belonging to the traffic stream. The roadway safety performance study is based on the traffic conflict technique applied to vehicle maneuvers obtained experimentally from a frame by frame analysis of video-taped traffic data. The authors also explored qualitatively the possible relationship between safety level and traffic level of service. This aspect is very important because this kind of roads represents a large part of non-urban highways in many countries.

scholarly journals Identifying the Most Significant Indicators of the Total Road Safety Performance Index- Case Study: European Union

2019 ◽  
Vol 4 (1-2) ◽  
Author(s):  
Milan Tešić ◽  
Elke Hermans ◽  
Krsto Lipovac ◽  
Dalibor Pešić
Keyword(s):  
Performance Index ◽  
Road Safety ◽  
Composite Index ◽  
Safety Performance ◽  
Data Envelopment ◽  
Safety Level ◽  
The Road ◽  
Wide Range ◽  
Selection Of

The review of the national and international literature dealing with the assessment of the road safety level has shown great efforts of the authors who aimed to define the methodology for calculating the composite road safety index on a territory (region, state, etc.). The procedure for obtaining a road safety composite index of an area has been largely harmonized. The question that has not been fully resolved yet concerns the selection of indicators. There is a wide range of road safety indicators used to show the road safety situation in a territory. The road safety performance index (RSPI) obtained on the basis of a larger number of safety performance indicators (SPIs) enables decision makers to more precisely define earlier goal- oriented actions. Recording a broader comprehensive set of SPIs helps identify the strengths and weaknesses of an area’s road safety system. Therefore, there is a need for calculating a road safety performance index with a limited number of indicators (RSPIlnn) which will provide a comparison of sufficient quality, of as many countries as possible. The application of the Data Envelopment Analysis (DEA) method and correlation analysis has helped to check if the RSPIlnn is likely to be of sufficient quality. A strong correlation between the RSPIlnn and the RSPI based on all indicators has been identified using the proposed methodology. This will help achieve the standardization of indicators including data collection procedures and selection of the key list of indicators that need to be monitored.

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.

Аpplying of high-frequency monopolar diathermocoagulation in the treatment of chronic pulpitis

2020 ◽  
Vol 1 (12) ◽  
pp. 40-42
Author(s):  
F. Yu. Daurova ◽  
D. I. Tomaeva ◽  
S. V. Podkopaeva ◽  
Yu. A. Taptun
Keyword(s):  
Root Canal ◽  
High Frequency ◽  
Antibacterial Effect ◽  
Comparison Group ◽  
Poor Quality ◽  
Endodontic Treatment ◽  
Root Canals ◽  
The Third ◽  
Before And After

Relevance: the reason for the development of complications in endodontic treatment is poor-quality instrumental treatment root canals.Aims: a study of the animicrobial action and clinical efficacy of high-frequency monopolar diathermocoagulation in the treatment of chronic forms of pulpitis.Materials and methods: 102 patients with various chronic forms of pulpitis were divided into three groups of 34 patients each. In the first two groups, high-frequency monopolar diathermocoagulation was used in endodontic treatment in different modes. In the third group, endodontic treatment was carried out without the use of diathermocoagulation (comparison group). The root canal microflora in chronic pulpitis in vivo was studied twice-before and after diathermocoagulation.Results: it was established that high-frequency monopolar diathermocoagulation in the effect mode is 3, power is 4 (4.1 W) and effect is 4, power is 4 (5.4 W) with an exposure time of 3 seconds, it has a pronounced antibacterial effect on all presented pathogenic microflora obtained from the root canals of the teeth.

scholarly journals Modelling of a Partially Loaded Road Tanker during a Braking-in-a-Turn Maneuver

Actuators ◽  
2018 ◽  
Vol 7 (3) ◽  
pp. 45 ◽  
Author(s):  
Frank Otremba ◽  
José Romero Navarrete ◽  
Alejandro Lozano Guzmán
Keyword(s):  
Road Safety ◽  
Load Transfer ◽  
Dynamic Interaction ◽  
Performance Measure ◽  
Lateral Stability ◽  
Safety Level ◽  
Factors Associated ◽  
Braking System ◽  
Factors Influencing ◽  
Fill Level

Road safety depends on several factors associated with the vehicle, to the infrastructure, as well as to the environment and experience of vehicle drivers. Concerning the vehicle factors influencing the safety level of an infrastructure, it has been shown that the dynamic interaction between the carried liquid cargo and the vehicle influences the operational safety limits of the vehicle. A combination of vehicle and infrastructure factors converge when a vehicle carrying liquid cargo at a partial fill level performs a braking maneuver along a curved road segment. Such a maneuver involves both longitudinal and lateral load transfers that potentially affect both the braking efficiency and the lateral stability of the vehicle. In this paper, a series of models are set together to simulate the effects of a sloshing cargo on the braking efficiency and load transfer rate of a partially filled road tanker. The model assumes the superposition of the roll and pitch independent responses, while the vehicle is equipped with Anti-lock braking System brakes (ABS) in the four wheels. Results suggest that cargo sloshing can affect the performance of the vehicle on the order of 2% to 9%, as a function of the performance measure considered. A dedicated ABS system could be considered to cope with such diminished performance.

scholarly journals Gametocyte carriage after seasonal malaria chemoprevention in Plasmodium falciparum infected asymptomatic children

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Abdullahi Ahmad ◽  
Aurelia Prom ◽  
John Bradley ◽  
Mamadou Ndiath ◽  
Blessed Etoketim ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Comparison Group ◽  
Conditional Logistic Regression ◽  
Gametocyte Carriage ◽  
Asymptomatic Children ◽  
Seasonal Malaria Chemoprevention ◽  
Before And After ◽  
Chi Squared ◽  
Comparison Groups ◽  
To Receive

Abstract Background Treatment of clinical Plasmodium falciparum malaria with sulfadoxine-pyrimethamine (SP) and amodiaquine (AQ) is associated with increased post-treatment gametocyte carriage. The effect of seasonal malaria chemoprevention (SMC) with SP and AQ on gametocyte carriage was assessed in asymptomatic P. falciparum infected children. Methods The study was carried out in eastern Gambia. Asymptomatic P. falciparum malaria infected children aged 24–59 months old who were eligible to receive SMC (SMC group) and children 5–8 years that were not eligible to receive SMC (comparison group) were recruited. Gametocytaemia was determined by molecular methods before and after SMC administration. Gametocyte carriage between the groups was compared using the chi-squared test and within-person using conditional logistic regression. Results During the 2017 and 2018 malaria transmission seasons, 65 and 75 children were recruited in the SMC and comparison groups, respectively. Before SMC administration, gametocyte prevalence was 10.7% (7/65) in the SMC group and 13.3% (10/75) in the comparison group (p = 0.64). At day 13 (IQR 12, 13) after SMC administration, this was 9.4% (5/53) in children who received at least the first dose of SMC treatment and 12.7% (9/71) for those in the comparison group (p = 0.57). Similarly, there was no difference in prevalence of gametocytes between children that adhered to all 3-day doses of SMC treatment 15.6% (5/32) and those in the comparison group (p = 0.68). In the SMC group, within-group gametocyte carriage was similar before and after SMC administration in children that received at least the first dose of SMC treatment (OR 0.6, 95% CI 0.14–2.51; p = 0.48) and in those that adhered to all 3-day doses of SMC treatment (OR 1.0, 95% CI 0.20–4.95; p = 1.0). Conclusion In this study with relative low gametocyte prevalence prior to SMC treatment, no evidence was observed that SMC treatment increased gametocyte carriage in asymptomatic P. falciparum malaria infected children.

scholarly journals Salivary Pro-Inflammatory Markers and Smoking Status Influences the Treatment Effectiveness of Periodontal Disease Patients with Hypertension

2021 ◽  
Vol 18 (14) ◽  
pp. 7364
Author(s):  
Kun-Tsung Lee ◽  
Zhu-Ling Guo ◽  
Nai-Chia Teng ◽  
Kuei-Ling Christine Hsu ◽  
I-Hui Chen ◽  
...  
Keyword(s):  
Periodontal Disease ◽  
Recovery Rate ◽  
Inflammatory Markers ◽  
Treatment Effectiveness ◽  
Smoking Status ◽  
Periodontal Diseases ◽  
Probing Depth ◽  
Before And After ◽  
Therapeutic Procedures ◽  
History Of

Background: Hypertension and periodontal diseases share several risk factors. Inflammation biomarkers in saliva are related to hypertension and periodontal disease. The aim of this study was to explore the role of the salivary inflammatory biomarkers in the treatment effectiveness of patients with hypertension and periodontal disease. Methods: This observational study enrolled 160 subjects diagnosed with periodontitis, 40 of which had a history of hypertension. All subjects had completed scaling and root planning therapeutic procedures within four weeks. The clinical periodontal parameters (i.e., bleeding on probing, plaque control record (PCR), and probing depth (PD)) were evaluated before and after the treatment. Pro-inflammatory markers were determined using a commercial kit. Results: The recovery rate (PD 4–9 mm) in non-hypertensive subjects was significantly higher than in hypertensive subjects (60.47% vs. 52.60%, respectively; p = 0.04). All clinical parameters, excluding PCR, positively correlated with salivary IL-1β at baseline and after completing treatment. Our results showed that increased salivary IL-1β levels were positively associated with decreased PCR (β = −27.65 and p = 0.05) and PD recovery rate (β = −17.05 and p = 0.02) in hypertensive subjects. Conclusions: The present study sheds important light on the clinical use of salivary pro-inflammatory cytokines as valuable biomarkers for predicting the treatment effectiveness of patients suffering from hypertension and periodontitis.

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