Objective: To investigate trends of motorcyclist fatalities and identify at-risk populations by motorcyclist demographics and crash characteristics.
Methods: We used the Fatality Analysis Reporting System (FARS) database (2000–2016) to track fatality rate trends, which were quantified by using Poisson mixed-effects regression models comparing 2000–2001 and 2007–2008, as well as 2009–2010 and 2015–2016.
Results: The overall fatality rate per 100,000 population increased from 2000 to 2016, defined by two trend lines—before and after the economic recession in 2008–2009. The overall fatality rate ratio between 2000–2001 and 2007–2008 was 1.60 [95% Confidence Interval (CI): 1.51–1.70], and between 2009–2010 and 2015–2016 was 1.09 (95% CI: 1.02–1.18). Fatality rates increased among all age groups, particularly for motorcyclists aged 60 and older. Those aged 18–29 had the highest fatality rates overall. Age-and-sex standardized state fatality rates were consistently highest in Wyoming, South Dakota, and South Carolina and lowest in Massachusetts, New York and New Jersey.
Conclusion: Motorcycle fatality rates increased overall and across all age groups between 2000 and 2016. Fatalities for the oldest riders showed the steadiest increasing trends. Results highlight the continued public health burden of motorcyclist fatalities and, by extension, the importance of improving motorcycle safety. 相似文献
Aboveground biomass (AGB) of forests is an important component of the global carbon cycle. In this study, Landsat ETM(+) images and field forest inventory data were used to estimate AGB of forests in Liping County, Guizhou Province, China. Three different vegetation indices, including simple ratio (SR), reduced simple ratio (RSR), and normalized difference vegetation index (NDVI), were calculated from atmospherically corrected ETM(+) reflectance images. A leaf area index (LAI) map was produced from the RSR map using a regression model based on measured LAI and RSR. The LAI map was then used to develop an initial AGB map, from which forest stand age was deduced. Vegetation indices, LAI, and forest stand age were together used to develop AGB estimation models for different forest types through a stepwise regression analysis. Significant predictors of AGB changed with forest types. LAI and NDVI were significant predictors of AGB for Chinese fir (R(2)=0.93). The model using LAI and stand age as predictors explained 94% of the AGB variance for coniferous forests. Stand age captured 79% of the AGB variance for broadleaved forests (R(2)=0.792). AGB of mixed forests was predicted well by LAI and SR (R(2)=0.931). Without differentiating among forest types, the model with SR and LAI as predictors was able to explain 90% of AGB variances of all forests. In Liping County, AGB shows a strong gradient that increases from northeast to southwest. About 64% of the forests have AGB in the range from 90 to 180 t ha(-1). 相似文献
Natural regeneration and the height-age structure of small-leaved linden (Tilia cordata Mill.) under a forest canopy were studied with regard to specific features of forest typology on the Ufa Plateau. For the first time, the height-age structure of linden undergrowth was analyzed by an anatomical method, which allowed accurate determination of the actual plant age and linear increment. The results of this analysis made it possible to reveal three periods in the development of linden undergrowth with respect to the linear growth rate and abundance of plants. More successful regeneration of linden was observed in open elements of relief. 相似文献