Objective: The objective of this article is to provide empirical evidence for safe speed limits that will meet the objectives of the Safe System by examining the relationship between speed limit and injury severity for different crash types, using police-reported crash data.
Method: Police-reported crashes from 2 Australian jurisdictions were used to calculate a fatal crash rate by speed limit and crash type. Example safe speed limits were defined using threshold risk levels.
Results: A positive exponential relationship between speed limit and fatality rate was found. For an example fatality rate threshold of 1 in 100 crashes it was found that safe speed limits are 40 km/h for pedestrian crashes; 50 km/h for head-on crashes; 60 km/h for hit fixed object crashes; 80 km/h for right angle, right turn, and left road/rollover crashes; and 110 km/h or more for rear-end crashes.
Conclusions: The positive exponential relationship between speed limit and fatal crash rate is consistent with prior research into speed and crash risk. The results indicate that speed zones of 100 km/h or more only meet the objectives of the Safe System, with regard to fatal crashes, where all crash types except rear-end crashes are exceedingly rare, such as on a high standard restricted access highway with a safe roadside design. 相似文献
Long-term stationary studies on the ecology of the northern mole vole (Ellobius talpinus Pall.), performed by the mark–recapture method from 1985 to 1997, have provided original data on population dynamics and structure. The analysis shows that, to reveal cyclic fluctuations of population size in this species, the period of three years should be taken as a unit of time for estimating the duration of one phase. The 12-year population cycle in E. talpinus has four distinct phases: an increase, a peak, a decline, and a minimum. At each phase, the population is characterized by certain features of family structure, age composition, birth and death rates, and the composition of migrants. 相似文献
BACKGROUND: The Yangtze Delta is one of the most developed regions in China and includes Shanghai, eight cities in Jiangsu province and eight cities in Zhejiang province. Meat consumption in this region has increased with economic growth, and most of the consumed meat is produced locally. The water quality of surface waters has deteriorated in recent years. An example was the huge blue-green algae bloom in Tai Lake in late May 2007, which affected millions of people's daily drinking water. However, animal husbandry is considered to be one of the main pollution sources. METHODS: Pollutants (NH3-N, total phosphorus (TP), and total nitrogen (TN)) excreted by livestock and poultry, and the resultant COD (chemical oxygen demand) and BOD (biochemical oxygen demand), were estimated using two different methods based on different data sets. RESULTS: The number of livestock and poultry has remained stable in the Yangtze Delta over the four years from 1999 to 2002, with the average number of pigs, cattle, sheep and poultry being 21.1 M, 0.4 M, 7.7 M and 597.6 M, respectively. Pollutants in livestock and poultry excreta estimated by Method I were: 0.12 Mt NH3-N, 0.11 Mt TP and 0.29 Mt TN, resulting in COD and BOD of 1.34 Mt and 1.30 Mt, respectively, while the estimations based on Method II were: 0.18 Mt NH3-N, 0.15 Mt TP and 0.40 Mt TN, resulting in COD and BOD of 1.95 Mt and 1.80 Mt, respectively. DISCUSSION: Pollutants excreted annually by livestock and poultry in the Yangtze Delta are estimated to be: 0.17 Mt NH3-N, 0.16 Mt TP and 0.42 Mt TN, giving rise to a COD of 1.86 Mt and a BOD of 1.72 Mt. Approximately 25% of this pollution was estimated to enter water bodies, which means that the annual pollutant load is 43,700 t NH3-N, 39,400 tTP, 104,600t TN with a COD of 465,000 tand a BOD of 430,100 t. Pollutants from animal husbandry were similar in magnitude to those from industrial wastewater. Pigs produced the most pollution, followed by poultry, cattle and sheep. The pollution load from animal husbandry in the Yangtze Delta is about twice the average level of the whole of China. CONCLUSIONS: Domestic wastewater was the main pollution source in the Yangtze Delta, followed by pollution from raising livestock and poultry and from industrial wastewater. The pollution load in Shanghai and Jiaxing were the greatest, followed by 7 cities of Jiangsu province (except Suzhou) and other cities of Zhejiang province and Suzhou. Pigs and poultry produced about 90% of the total pollutants from animal husbandry. RECOMMENDATIONS AND PERSPECTIVES: The local governments, especially in Shanghai and Jiaxing, should focus their attention on the pollution produced by livestock and poulrry. Controlling pollution from pigs and poultry will have the greatest impact in this region. Control of pollution will be facilitated by the development of large-scale livestock and poultry farming units and a shift away from small scale husbandry. 相似文献