Estimating seat belt effectiveness using matched-pair cohort methods.
ABSTRACT Using US data for 1986-1998 fatal crashes, we employed matched-pair analysis methods to estimate that the relative risk of death among belted compared with unbelted occupants was 0.39 (95% confidence interval (CI) 0.37-0.41). This differs from relative risk estimates of about 0.55 in studies that used crash data collected prior to 1986. Using 1975-1998 data, we examined and rejected three theories that might explain the difference between our estimate and older estimates: (1) differences in the analysis methods; (2) changes related to car model year; (3) changes in crash characteristics over time. A fourth theory, that the introduction of seat belt laws would induce some survivors to claim belt use when they were not restrained, could explain part of the difference in our estimate and older estimates; but even in states without seat belt laws, from 1986 through 1998, the relative risk estimate was 0.45 (95% CI 0.39-0.52). All of the difference between our estimate and older estimates could be explained by some misclassification of seat belt use. Relative risk estimates would move away from 1, toward their true value, if misclassification of both the belted and unbelted decreased over time, or if the degree of misclassification remained constant, as the prevalence of belt use increased. We conclude that estimates of seat belt effects based upon data prior to 1986 may be biased toward 1 by misclassification.
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ABSTRACT: Characteristics of cars, such as mass and age, play a significant role in crash severity, but their effect are difficult to quantify because of the great number of factors altering the outcome of a real world accident. In order to focus on the crashworthiness of cars, we examine risk factors of severity suffered by the drivers involved in two-car accidents recorded by the police between 1996 and 2000 in France. From them, we build three matched case-control studies where both drivers have different severity levels: killed or injured vs. uninjured; severely injured vs. slightly injured; and killed vs. injured. Odds-Ratios are estimated by conditional logistic regression. The risk of being injured decreases with the weight of the car, coming to six times lower when driving a 1200 kg or more car compared to a 800 kg or less car. The risk of being killed rather than injured increases with the age of the car, reaching the highest value of height when comparing 1990 or before cars to the most recent ones. As expected, highest risks of death or injury are shown for side-impacted cars, seat belt wearing is confirmed as being very protective and drivers of vehicles with frontal airbag are less often injured. The risk of being injured or killed increases with the age of the driver, and is higher for women. These characteristics of drivers are associated with both their way of driving and their capacity to withstand an impact, and it was then necessary to adjust our estimates on them. Our results show that recent cars provide a better protection, but confirm that the compatibility of cars with each other according to their weight is a big issue. It also corroborates the necessity of adaptative safety devices for taking the characteristics of a car occupant into account.
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ABSTRACT: Background: The airbags can reduce even 50% of passenger injuries in a car accident. When they are not used properly, they can cause serious injuries. There have been reported several cases with fatal injuries. Aim: The aim of this study was to review the dangers that result from the incorrect use of airbags. Methods: A thorough review, included bibliography research from both the review and the research literature in different databases was done, such as pubmed, scopus and heallink. Results: Many injuries from airbags have been reported in the literature. Most of them are burns from the produced gases during the development of the airbag. At the beginning of their use, airbags opened with great speed. As a result there were a lot of injuries. For this reason, it was proposed to reduce the speed of development. Often problems have the eyes and ears. Less frequent are injuries or fractures of the upper and lower extremities. Rarely, cervical spine and ribs injures from the airbag. We found one case report of placental abruption after airbag deployment in a woman driver. On contact with the airbag, passenger can also injure aorta or heart. Conclusions: The airbags provide safety to the occupants of cars and reduce the mortality even at 50%. When not used in accordance with international standards can cause serious injuries. The airbags should always be used in conjunction with seatbelts.Health Science Journal 01/2011; 5(4):262.
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ABSTRACT: The current study contributes to the existing injury severity modeling literature by developing a multivariate probit model of injury severity and seat belt use decisions of both drivers involved in two-vehicle crashes. The modeling approach enables the joint modeling of the injury severity of multiple individuals involved in a crash, while also recognizing the endogeneity of seat belt use in predicting injury severity levels as well as accommodating unobserved heterogeneity in the effects of variables. The proposed model is applied to analyze the injury severity of drivers involved in two-vehicle road crashes in Denmark. The empirical analysis provides strong support for the notion that people offset the restraint benefits of seat belt use by driving more aggressively. Also, men and those individuals driving heavy vehicles have a lower injury risk than women and those driving lighter vehicles, respectively. At the same time, men and individuals driving heavy vehicles pose more of a danger to other drivers on the roadway when involved in a crash. Other important determinants of injury severity include speed limit on roadways where crash occurs, the presence (or absence) of center dividers (median barriers), and whether the crash involves a head-on collision. These and other results are discussed, along with implications for countermeasures to reduce injury severities in crashes. The analysis also underscores the importance of considering injury severity at a crash level, while accommodating seat belt endogeneity effects and unobserved heterogeneity effects.Transportation Research Part B Methodological 04/2013; 50. DOI:10.1016/j.trb.2013.01.007 · 2.94 Impact Factor