scholarly journals Comparison of Crash Modification Factors for Engineering Treatments Estimated by Before–After Empirical Bayes and Propensity Score Matching Methods

2020 ◽  
pp. 036119812095377
Author(s):  
Bo Lan ◽  
Raghavan Srinivasan
Keyword(s):  
Propensity Score ◽  
Regression Models ◽  
Empirical Bayes ◽  
Regression To The Mean ◽  
Cross Sectional ◽  
Matching Methods ◽  
Before And After ◽  
Crash Modification Factors ◽  
The Mean ◽  
Cross Sectional Studies

Cross-sectional and the empirical Bayes (EB) before–after are two of the most common methods for estimating crash modification factors (CMFs). The EB before–after method has now been accepted as one way of addressing the potential bias caused by the regression to the mean problem. However, sometimes before–after methods may not feasible because of the lack of data from before and after periods. In those cases, researchers rely on cross-sectional studies to develop CMFs. However, cross-sectional studies may provide biased CMFs through confounding. The propensity score (PS) matching method, along with cross-sectional regression models, is one of the methods that can be used to address confounding. Though PS methods are widely used in epidemiology and other studies, there are only a few studies that have used PS matching methods to estimate CMFs. The intent of this study is to evaluate and compare the performance of cross-sectional regression models using PS matching methods with the results from the EB and traditional cross-sectional methods. The comparisons were conducted using two carefully selected simulated datasets. The results indicate that optimal propensity score distance (PSD) matching with maximum variable ratio of 5 performed quite well compared with the EB before–after and the traditional cross-sectional methods.

Before–After Evaluation of the Realignment of Horizontal Curves on Rural Two-Lane Roads

2018 ◽  
Vol 2672 (30) ◽  
pp. 43-52
Author(s):  
Raghavan Srinivasan ◽  
Daniel Carter ◽  
Craig Lyon ◽  
Matthew Albee
Keyword(s):  
Empirical Bayes ◽  
Cross Sectional ◽  
Road Crashes ◽  
Horizontal Curves ◽  
Run Off ◽  
Fatal Crashes ◽  
Site Characteristics ◽  
Before And After ◽  
Crash Modification Factors ◽  
Cross Sectional Studies

This study determined the crash modification factors (CMFs) associated with horizontal curve realignment using the before–after empirical Bayes method and compared the results from published CMFs from cross-sectional studies. This evaluation used data from rural, two-lane roads in California, North Carolina, and Ohio. The evaluation revealed a 68% reduction in total crashes, a 74% reduction in injury and fatal crashes, a 78% reduction in run-off-road and fixed object crashes, a 42% reduction in crashes during dark conditions, and an 80% reduction in wet-road crashes, all of which were statistically significant at the 95% confidence level. The results pertain to a range of site characteristics, the most important of which is the range of before and after degree of curve. The average degrees of curve in the before and after periods were 18.1 (with a minimum of 3.2 and a maximum of 52.1) and 6.9 (with a minimum of 0.0 and a maximum of 16.3), respectively. The average central angle of the curves was approximately 42° (with a minimum of 1 and a maximum of 117). The CMFs from this before–after evaluation are lower compared to CMFs estimated from two previous cross-sectional studies. There is a need for further research with a larger sample of sites to assess the reliability of the CMFs obtained from this before–after evaluation.

Developing Crash Modification Factors for Horizontal Curves on Rural Two-Lane Undivided Highways Using a Cross-Sectional Study

2017 ◽  
Vol 2636 (1) ◽  
pp. 53-61 ◽  
Author(s):  
Lingtao Wu ◽  
Dominique Lord ◽  
Srinivas Reddy Geedipally
Keyword(s):  
Regression Models ◽  
Cross Sectional Study ◽  
Highway Safety ◽  
Sectional Study ◽  
Cross Sectional ◽  
Highway Safety Manual ◽  
Horizontal Curves ◽  
Before And After ◽  
Crash Modification Factors ◽  
Curve Radius

Horizontal curves have been identified as experiencing more crashes than tangent sections on roadways, especially on rural two-lane highways. The first edition of the Highway Safety Manual provides crash modification functions (CM functions) for curves on rural two-lane highways. The CM functions proposed in the manual may suffer from both outdated data and analysis technique. Before-and-after studies are usually the preferred method for estimating the safety effects of treatments. Unfortunately, this method is not feasible for curves. Previous studies have frequently used regression models for developing CM functions for horizontal curves. As recently documented in the literature, some potential problems exist with using regression models to develop crash modification factors. This research utilized a cross-sectional study to develop curvature CM functions. Curves located on Texas rural two-lane undivided highways were divided into a number of bins based on the curve radius. Safety was predicted with the assumption that these curves had been tangents. The observed number of crashes that occurred on the curves was compared with the dummy tangents and for different bins. The results showed that the horizontal curve radius has a significant role in the risk of a crash. From these results, a new CM function was developed. The prediction performance of the Highway Safety Manual CM function was compared with the new CM function in this study and another function that was recently proposed in the literature. It was found that the new CM function documented in this study outperformed both.

scholarly journals Resilience and vulnerability of maternity services in Zimbabwe: a comparative analysis of the effect of Covid-19 and lockdown control measures on maternal and perinatal outcomes, a single-centre cross-sectional study at Mpilo Central Hospital

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Clare Shakespeare ◽  
Handsome Dube ◽  
Sikhangezile Moyo ◽  
Solwayo Ngwenya
Keyword(s):  
Perinatal Outcomes ◽  
Control Measures ◽  
Central Hospital ◽  
Cross Sectional ◽  
Maternity Services ◽  
Before And After ◽  
The Mean ◽  
Significant Change ◽  
The Impact ◽  
Mpilo Central Hospital

Abstract Background On the 27th of March 2020 the Zimbabwean government declared the Covid-19 pandemic a ‘national disaster’. Travel restrictions and emergency regulations have had significant impacts on maternity services, including resource stock-outs, and closure of antenatal clinics during the lockdown period. Estimates of the indirect impact of Covid-19 on maternal and perinatal mortality was expected it to be considerable, but little data was yet available. This study aimed to examine the impact of Covid-19 and lockdown control measures on non-Covid outcomes in a government tertiary level maternity unit in Bulawayo, Zimbabwe, by comparing maternal and perinatal morbidity and mortality before, and after the lockdown was implemented. Methods This was a retrospective, observational study, using a cross-sectional design to compare routine monthly maternal and perinatal statistics three months before and after Covid-19 emergency measures were implemented at Mpilo Central Hospital. Results Between January-March and April-June 2020, the mean monthly deliveries reduced from 747.3 (SD ± 61.3) in the first quarter of 2020 to 681.0 (SD ± 17.6) during lockdown, but this was not statistically significant, p = 0.20. The Caesarean section rates fell from a mean of 29.8% (SD ± 1.7) versus 28.0% (SD ± 1.7), which was also not statistically significant, p = 0.18. During lockdown, the percentage of women delivering at Mpilo Central Hospital who were booked at the hospital fell from a mean of 41.6% (SD ± 1.1) to 35.8% (SD ± 4.3) which was statistically significant, p = 0.03. There was no significant change, however, in maternal mortality or severe maternal morbidity (such as post-partum haemorrhage (PPH), uterine rupture, and severe preeclampsia/eclampsia), stillbirth rate or special care baby unit admission. There was an increase in the mean total number of early neonatal deaths (ENND) (mean 18.7 (SD ± 2.9) versus 24.0 (SD ± 4.6), but this was not statistically significant, p = 0.32. Conclusions Overall, maternity services at Mpilo showed resilience during the lockdown period, with no significant change in maternal and perinatal adverse outcomes, with the same number of man-hours worked before and during the lockdown Maternal and perinatal outcomes should continue to be monitored to assess the impact of Covid-19 and the lockdown measures as the pandemic in Zimbabwe unfolds. Further studies would be beneficial to explore women’s experiences and understand how bookings and deliveries at local clinics changed during this time.

scholarly journals Examining the Effects of the Sacramento Dockless E-Bike Share on Bicycling and Driving

2021 ◽  
Vol 13 (1) ◽  
pp. 368
Author(s):  
Dillon T. Fitch ◽  
Hossain Mohiuddin ◽  
Susan L. Handy
Keyword(s):  
Travel Behavior ◽  
Regression Models ◽  
Population Level ◽  
Panel Survey ◽  
Multilevel Regression ◽  
Combine Data ◽  
Cross Sectional ◽  
Individual Level ◽  
Before And After ◽  
Bike Share

One way cities are looking to promote bicycling is by providing publicly or privately operated bike-share services, which enable individuals to rent bicycles for one-way trips. Although many studies have examined the use of bike-share services, little is known about how these services influence individual-level travel behavior more generally. In this study, we examine the behavior of users and non-users of a dockless, electric-assisted bike-share service in the Sacramento region of California. This service, operated by Jump until suspended due to the coronavirus pandemic, was one of the largest of its kind in the U.S., and spanned three California cities: Sacramento, West Sacramento, and Davis. We combine data from a repeat cross-sectional before-and-after survey of residents and a longitudinal panel survey of bike-share users with the goal of examining how the service influenced individual-level bicycling and driving. Results from multilevel regression models suggest that the effect of bike-share on average bicycling and driving at the population level is likely small. However, our results indicate that people who have used-bike share are likely to have increased their bicycling because of bike-share.

What Is the Impact of Prior Authorization on the Incidence of Pediatric Tonsillectomy?

2020 ◽  
pp. 019459982096963
Author(s):  
Vanessa F. Torrecillas ◽  
Kaden Neuberger ◽  
Alexander Ramirez ◽  
Paul Krakovitz ◽  
Jeremy D. Meier
Keyword(s):  
Elective Surgery ◽  
Lag Time ◽  
Cross Sectional Study ◽  
Health Claims ◽  
Third Party ◽  
Prior Authorization ◽  
Cross Sectional ◽  
Before And After ◽  
The Mean ◽  
The Impact

Objective Third-party payers advocate for prior authorization (PA) to reduce overutilization of health care resources. The impact of PA in elective surgery is understudied, especially in cases where evidence-based clinical practice guidelines define operative candidacy. The objective of this study is to investigate the impact of PA on the incidence of pediatric tonsillectomy. Study Design Cross-sectional study. Setting Health claims database from a third-party payer. Methods Any pediatric patient who had evaluation for tonsillectomy from 2016 to 2019 was eligible for inclusion. A time series analysis was used to evaluate the change in incidence of tonsillectomy before and after PA. Lag time from consultation to surgery before and after PA was compared with segmented regression. Results A total of 10,047 tonsillectomy claims met inclusion and exclusion criteria. Female patients made up 51% of claims, and the mean age was 7.9 years. Just 1.5% of claims were denied after PA implementation. There was no change in the incidence of tonsillectomy for all plan types ( P = .1). Increased lag time from consultation to surgery was noted immediately after PA implementation by 2.38 days (95% CI, 0.23-4.54; P = .030); otherwise, there was no significant change over time ( P = .98). Conclusion A modest number of tonsillectomy claims were denied approval after implementation of PA. The value of PA for pediatric tonsillectomy is questionable, as it did not result in decreased incidence of tonsillectomy in this cohort.

Effect of Honey and Green Tea Solutions on Streptococcus mutans

2015 ◽  
Vol 39 (5) ◽  
pp. 435-441
Author(s):  
F Abdelmegid ◽  
M Al-Agamy ◽  
A Alwohaibi ◽  
H Ka'abi ◽  
F Salama
Keyword(s):  
Streptococcus Mutans ◽  
Green Tea ◽  
Saliva Sample ◽  
Post Intervention ◽  
Cross Sectional ◽  
Colony Forming Unit ◽  
Before And After ◽  
The Mean ◽  
Mouth Rinsing

Objectives: The aim of this cross-sectional in vivo study was to assess the effect of green tea and honey solutions on the level of salivary Streptococcus mutans. Study design: A convenient sample of 30 Saudi boys aged 7–10 years were randomly assigned into 2 groups of 15 each. Saliva sample was collected for analysis of level of S. mutans before rinsing. Commercial honey and green tea were prepared for use and each child was asked to rinse for two minutes using 10 mL of the prepared honey or green tea solutions according to their group. Saliva samples were collected again after rinsing. The collected saliva samples were prepared and colony forming unit (CFU) of S. mutans per mL of saliva was calculated. Results: The mean number of S. mutans before and after rinsing with honey and green tea solutions were 2.28* 108(2.622*108), 5.64 *107(1.03*108), 1.17*109(2.012*109) and 2.59*108 (3.668*108) respectively. A statistically significant reduction in the average number of S. mutans at baseline and post intervention in the children who were assigned to the honey (P=0.001) and green tea (P=0.001) groups was found. Conclusions: A single time mouth rinsing with honey and green tea solutions for two minutes effectively reduced the number of salivary S. mutans of 7–10 years old boys.

scholarly journals Biomarkers of environmental manganese exposure and associations with childhood neurodevelopment: a systematic review and meta-analysis

2020 ◽  
Vol 19 (1) ◽  
Author(s):  
Weiwei Liu ◽  
Yongjuan Xin ◽  
Qianwen Li ◽  
Yanna Shang ◽  
Zhiguang Ping ◽  
...  
Keyword(s):  
Sex Differences ◽  
Motor Skills ◽  
Meta Analysis ◽  
Fold Increase ◽  
Behavioral Performance ◽  
Cross Sectional ◽  
Manganese Exposure ◽  
Negative Effect ◽  
The Mean ◽  
Cross Sectional Studies

Abstract Background Although prior studies showed a correlation between environmental manganese (Mn) exposure and neurodevelopmental disorders in children, the results have been inconclusive. There has yet been no consistent biomarker of environmental Mn exposure. Here, we summarized studies that investigated associations between manganese in biomarkers and childhood neurodevelopment and suggest a reliable biomarker. Methods We searched PubMed and Web of Science for potentially relevant articles published until December 31th 2019 in English. We also conducted a meta-analysis to quantify the effects of manganese exposure on Intelligence Quotient (IQ) and the correlations of manganese in different indicators. Results Of 1754 citations identified, 55 studies with 13,388 subjects were included. Evidence from cohort studies found that higher manganese exposure had a negative effect on neurodevelopment, mostly influencing cognitive and motor skills in children under 6 years of age, as indicated by various metrics. Results from cross-sectional studies revealed that elevated Mn in hair (H-Mn) and drinking water (W-Mn), but not blood (B-Mn) or teeth (T-Mn), were associated with poorer cognitive and behavioral performance in children aged 6–18 years old. Of these cross-sectional studies, most papers reported that the mean of H-Mn was more than 0.55 μg/g. The meta-analysis concerning H-Mn suggested that a 10-fold increase in hair manganese was associated with a decrease of 2.51 points (95% confidence interval (CI), − 4.58, − 0.45) in Full Scale IQ, while the meta-analysis of B-Mn and W-Mn generated no such significant effects. The pooled correlation analysis revealed that H-Mn showed a more consistent correlation with W-Mn than B-Mn. Results regarding sex differences of manganese associations were inconsistent, although the preliminary meta-analysis found that higher W-Mn was associated with better Performance IQ only in boys, at a relatively low water manganese concentrations (most below 50 μg/L). Conclusions Higher manganese exposure is adversely associated with childhood neurodevelopment. Hair is the most reliable indicator of manganese exposure for children at 6–18 years of age. Analysis of the publications demonstrated sex differences in neurodevelopment upon manganese exposure, although a clear pattern has not yet been elucidated for this facet of our study.

Beating Yourself: How Do Runners Improve Their Own Records?

2020 ◽  
Vol 15 (3) ◽  
pp. 437-440 ◽  
Author(s):  
Carl Foster ◽  
Jos J. de Koning ◽  
Christian Thiel ◽  
Bram Versteeg ◽  
Daniel A. Boullosa ◽  
...  
Keyword(s):  
Coefficient Of Variation ◽  
Mean Velocity ◽  
Cross Sectional ◽  
Pacing Strategy ◽  
Average Coefficient ◽  
Before And After ◽  
Cross Sectional Studies ◽  
World Records ◽  
Elite Runners

Background: Pacing studies suggest the distribution of effort for optimizing performance. Cross-sectional studies of 1-mile world records (WRs) suggest that WR progression includes a smaller coefficient of variation of velocity. Purpose: This study evaluates whether intraindividual pacing used by elite runners to break their own WR (1 mile, 5 km, and 10 km) is related to the evolution of pacing strategy. We provide supportive data from analysis in subelite runners. Methods: Men’s WR performances (with 400-m or 1-km splits) in 1 mile, 5 km, and 10 km were retrieved from the IAAF database (from 1924 to present). Data were analyzed relative to pacing pattern when a runner improved their own WR. Similar analyses are presented for 10-km performance in subelite runners before and after intensified training. Results: WR performance was improved in 1 mile (mean [SD]: 3:59.4 [11.2] to 3:57.2 [8.6]), 5 km (13:27 [0:33] to 13:21 [0:33]), and 10 km (28:35 [1:27] to 28:21 [1:21]). The average coefficient of variation did not change in the 1 mile (3.4% [1.8%] to 3.6% [1.6%]), 5 km (2.4% [0.9%] to 2.2% [0.8%]), or 10 km (1.4% [0.1%] to 1.5% [0.6%]) with improved WR. When velocity was normalized to the percentage mean velocity for each race, the pacing pattern was almost identical. Very similar patterns were observed in subelite runners in the 10 km. When time improved from 49:20 (5:30) to 45:56 (4:58), normalized velocity was similar, terminal RPE increased (8.4 [1.6] to 9.1 [0.8]), coefficient of variation was unchanged (4.4% [1.1%] to 4.8% [2.1%]), and VO2max increased (49.8 [7.4] to 55.3 [8.8] mL·min−1·kg−1). Conclusion: The results suggest that when runners break their own best performances, they employ the same pacing pattern, which is different from when WRs are improved in cross-sectional data.

scholarly journals Association between Abdominal Fat (DXA) and Its Subcomponents (CT Scan) before and after Weight Loss in Obese Postmenopausal Women: A MONET Study

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Caroline Y. Doyon ◽  
Martin Brochu ◽  
Virginie Messier ◽  
Marie-Ève Lavoie ◽  
May Faraj ◽  
...  
Keyword(s):  
Weight Loss ◽  
Ct Scan ◽  
Postmenopausal Women ◽  
Caloric Restriction ◽  
Subcutaneous Fat ◽  
Abdominal Fat ◽  
Radiation Doses ◽  
Cross Sectional ◽  
Before And After ◽  
Cross Sectional Studies

Introduction. Subcutaneous fat (ScF) and visceral fat (VF) measurements using CT scan are expensive and may imply significant radiation doses. Cross-sectional studies using CT scan showed that ScF and VF are significantly correlated with abdominal fat measured by DXA (AF-DXA). The association has not been studied after a weight loss.Objective. To determine (1) the associations between AF-DXA and ScF and VF before and after weight loss and (2) the associations between their changes.Methods. 137 overweight/obese postmenopausal women were divided in two groups (1-caloric restriction or 2-caloric restriction + resistance training). AF was assessed using DXA and CT scan.Results. Correlations between AF-DXA and ScF (before:r=0.87, after;r=0.87;P<.01) and, AF-DXA and VF (before:r=0.61, after;r=0.69;P<.01) are not different before and after the weight loss. Correlations between delta AF-DXA and delta ScF (r=0.72;P<.01) or delta VF (r=0.51;P<.01) were found.Conclusion. The use of AF-DXA as a surrogate for VF after weight loss is questionable, but may be interesting for ScF.

Sign in / Sign up

Export Citation Format

Share Document