Prevention effectiveness of rollover protective structures--Part III: Economic analysis

The purpose of this part of the study is to assess the costs and benefits of either installing rollover protective structures (ROPS) on tractors lacking ROPS and for which ROPS are available or replacing the tractors with newer ROPS-equipped ones, relative to doing nothing. The methods used are cost-effectiveness and cost-benefit analyses. The cost-effectiveness analysis shows that compared to the "do nothing" strategy, the "install ROPS" strategy would cost $489,373 per injury averted and the "replace tractor" strategy would cost $14.3 million per injury averted over a 23-year period. The cost-benefit analysis shows that compared to the "do nothing" strategy, the "install ROPS" strategy would save society $1.5 billion while the "replace tractor" strategy would cost society $18.7 billion. While both the "install ROPS" and the "replace tractor" strategies are effective at saving lives and preventing injuries, this study has concluded that the preferred strategy in terms of cost-effectiveness is to "install ROPS" on tractors lacking them and for which ROPS are available.     

Prevention effectiveness of rollover protective structures--Part I: Strategy evolution

This is the first of three articles that evaluate the health and economic consequences of the use of rollover protective structures (ROPS) on agricultural tractors. The effectiveness of ROPS delivered through alternative intervention strategies is the subject of the three-part study. This part of the study reviews and assesses the evolution of interventions that are known to prevent injuries incurred as a result of tractor overturns. The method used is historical analysis framed against a prevention effectiveness model used by the U.S. Centers for Disease Control and Prevention. Two intervention strategies were found to be potentially effective in preventing injuries from tractor overturns. These strategies are either to install a ROPS on tractors that lack a ROPS or to replace the tractor with one that has a ROPS already mounted. Other prevention factors include the effectiveness and use of seatbelts and the integrity of the ROPS system during an overturn.     

Installing a cost-effective rollover protective structure (CROPS): a cost-effectiveness analysis

Cost-effective rollover protective structures (CROPS) are tractor model-specific rollover protective structures (ROPS) that are as effective as existing ROPS retrofits (passed standardized structural static testing such as SAE J2194), but less costly (less than one-half the cost of existing ROPS retrofits). This study estimated the expected effects and costs at a per-tractor level for two options: No-CROPS and Install-CROPS. Expected injuries per tractor were 0.00169 with no CROPS and 0.00016 with CROPS installed, resulting in 0.00153 injuries prevented per tractor over a 20-year period. Expected costs were $457 and $248 with and without CROPS, respectively, over the same time period, giving the cost per injury prevented as $136,601. Comprehensive sensitivity analyses indicated that the probability of an overturn is one of the most important variables. When the cost of intervention ($1,000 for purchasing, shipping, and installation of ROPS retrofit) is used in the analysis, the cost-effectiveness ratio is $497,000 per injury prevented over the 20-year period. Thus, installing CROPS instead of existing ROPS retrofits improved the cost-effectiveness ratio substantially, with a 73% reduction in the net cost per injury prevented.     

A stable dynamic cohort analysis of installing cost-effective rollover protective structures (CROPS)

Cost-effective rollover protective structures (CROPS) are less costly model-specific rollover protective structure (ROPS) retrofits that are being developed and evaluated with the hope of increasing adoption and eventually preventing or mitigating injuries due to tractor overturns. A dynamic cohort of the estimated retrofittable non-ROPS tractors (accounting for attrition due to aging) was tracked over a 20-year period to determine the expected costs, as well as the expected number of fatal and non-fatal injuries resulting from tractor overturns. Two alternatives were tracked: No-ROPS and Install-CROPS. For a starting cohort size of 1,065,164 (an estimate for the year 2004), the Install-CROPS option prevented an estimated total of 878 (192 fatal and 686 non-fatal) injuries over the 20-year period. Expected costs were $513 million (cost of installing CROPS on all the non-ROPS tractors plus cost of the associated injuries) and $284 million (cost of injuries resulting from the No-ROPS option) over the same time period. Thus, the net cost per injury prevented was $260,820. When the cost of intervention ($1000 for purchasing, shipping, and installation of existing ROPS retrofit) was used in the analysis, the cost-effectiveness ratio was $927,000 per injury prevented over the 20-year period. Thus, installing CROPS instead of existing ROPS retrofits improved the cost-effectiveness ratio substantially, with a 72% reduction in the net cost per injury prevented.     

A survey of tractors and rollover protective structures in Washington State

A survey of farms in Washington State was conducted to determine tractor characteristics and the presence of rollover protective structures (ROPS) in a state with more inclusive rules on tractor retrofitting than federal regulations. A total of 544 valid surveys were completed from a proportional random sample across different types of farms. Responders indicated that 58% of tractors overall were equipped with ROPS, and 42% of the tractors without ROPS were exempt from the state rules. Seatbelts on tractors equipped with ROPS were reportedly used "sometimes" or more 30% of the time, and 17% of these tractors had no seatbelt installed. Tractors used for row crop farming were significantly more likely to be equipped with ROPS than those used for tree, vine, or hops farming. Older tractors were used for fewer hours, were less likely to be ROPS-equipped, and were less likely to be operated while wearing a seatbelt. The results were consistent with a positive effect of the Washington State ROPS requirements, demonstrated by the increased percentage of ROPS-equipped pre-1976 tractors, as compared to other states, and by the difference between ROPS-equipped tractors in exempt and non-exempt types of farming. The results point to the need for prevention activities to increase seatbelt use on ROPS-equipped tractors, and for further development of practical protection for tractors operating under overhead obstacles.     

Evaluation of engineering plastic for rollover protective structure (ROPS) mounting

Agriculture has one of the highest fatality rates of any industry in America. Tractor rollovers are a significant contributor to the high death rate. Rollover protective structures (ROPS) have helped lower these high fatality rates on full-size tractors. However, a large number of older tractors still do not use ROPS due to the difficulty of designing and creating a mounting structure. To help reduce this difficulty, engineering plastics were evaluated for use in a ROPS mounting structure on older tractors. The use of engineering plastics around axle housings could provide a uniform mounting configuration as well as lower costs for aftermarket ROPS. Various plastics were examined through shear testing, scale model testing, and compressive strength testing. Once a material was chosen based upon strength and cost, full-scale testing of the plastic's strength on axle housings was conducted. Finally, a mounting structure was tested in static ROPS tests, and field upset tests were performed in accordance with SAE Standard J2194. Initial tests revealed that the ROPS mounting structure and axle housing combination had higher torsional strength with less twisting than the axle housing alone. An engineering plastic ROPS mounting structure was easily successful in withstanding the forces applied during the static longitudinal and lateral ROPS tests. Field upset testing revealed that the mounting structure could withstand the impact loads seen during actual upsets without a failure. During both static testing and field upset testing, no permanent twisting of the mounting structure was found. Engineering plastic could therefore be a viable option for a universal ROPS mounting structure for older tractors.     

工程车辆翻车过程中两点式安全带约束效能分析

为了研究工程车辆翻车过程中驾驶员的动态响应,建立了某工程车辆90°侧翻的仿真模型。模拟有无两点式安全带、有无座椅扶手时50百分位和95百分位两种假人的运动状态,进而分析了在翻车过程中安全带对于不同身材驾驶员的约束作用以及与座椅扶手间的关系。结果表明：佩戴安全带减少了驾驶员被抛出车外造成严重伤害的可能;身材高大的驾驶员在翻车过程中头部和躯干偏离距离更大,增加了与驾驶室内坚硬部件接触碰撞的风险。安全带与座椅扶手配合使用,减小了假人头部的偏移量,从而降低头部与驾驶室内部部件发生碰撞造成严重伤害的可能,约束效果更佳。     

Initial rollover effectiveness evaluation of an alternative seat belt design for agricultural tractors

A test program was conducted to determine the effectiveness of a seat belt restraint in preventing occupant movement in a rollover accident. A baseline type-2 seat belt (pelvic and torso restraint), and an improved type-2 seat belt restraint, both designed to restrict occupant motion in a rollover accident, were tested in a rollover restraints tester (RRT). Each seat belt was placed on a H-III 50th percentile male dummy and testing conducted at a single roll rate and two D-ring adjustment positions. Each test simulated what was approximately a 260 degrees per second rollover parallel to the longitudinal axis of the tractor with the top of the ROPS impacting the ground after 180 degrees of roll. Forces on the dummy's head and neck were measured, and video was taken to measure the head motion in the x-, y-, and z-axis of the dummy. The average vertical, forward, and lateral head movement in the baseline seat belt was 144, 222, and 184 mm, respectively, when the adjustable D-ring anchorage supporting the shoulder belt was in its lowest position. At the lowest D-ring height, the shoulder belt became ineffective and the seat belt performance became similar to a type-1 restraint (required for tractors with ROPS) resulting in increased vertical, forward, and lateral movement. The improved restraint reduced vertical head movement by as much as 75% without increasing head and neck loads above established injury criteria. Testing seat belts for rollover effectiveness will become increasingly important as seat belt usage on tractors with ROPS increases.     

考虑路面激励的车辆侧翻仿真分析

为了能够有效地反映路面激励与转向输入引起的车辆侧翻特性,提出了一个能够同时考虑路面输入与转向操纵的联合车辆侧翻模型。利用Matlab/Simulink搭建了联合模型的仿真模型,并采用Adams车辆模型验证了联合模型的有效性。在此基础之上,通过开展仿真试验分析了路面等级、行驶车速、转向盘操纵速度等参数对车辆侧倾状态的影响。研究结果表明:联合模型能够较好地反映车辆在转向输入、路面输入耦合工况下的侧倾状态。该研究为车辆侧翻研究提供了有效的参考模型。     

Net monetary benefit of cost-effective rollover protective structures (CROPS): an estimate of the potential benefits of the CROPS research project

This study builds on an earlier study to examine the net monetary benefit of installing cost-effective rollover protective structures (CROPS) instead of utilizing existing ROPS retrofits for all estimated non-ROPS tractors in the year 2004. With the conservative estimates used in the analyses, results indicate that compared to the baseline option (no protective structure), the Install-ROPS option results in a loss of $310 million to society, while the Install-CROPS option results in a net monetary benefit of $276 million over a 20-year period. A comprehensive sensitivity analysis indicated that, for the extreme values (estimates) used, the estimated net monetary benefit is most sensitive to the probability of tractor overturn. Break-even analysis indicated that the unit cost of intervention for the Install-CROPS option can increase by about 58% and still be able to pay for itself. Even when the minimal unit cost of intervention for ROPS is used, the payback period is reduced substantially for the Install-CROPS option, by almost half the payback period. Finally, compared to existing ROPS retrofits, the net monetary benefit is $586 million, representing an estimate of the potential benefits of the CROPS research.     

Adoption of rollover protective structures (ROPS) on U.S. farm tractors by state: 1993-1995, 2001, and 2004

This research compares state-level rollover protective structure (ROPS) prevalence rates from the early and mid-1990s to those observed in the years 2001 and 2004. In addition, state-level ROPS prevalence rates are compared to state-level tractor overturn fatality rates. Tractor data for 1993-1995 and for 2001 and 2004 for all tractors and ROPS-equipped tractors in use on U.S. farms were derived from surveys conducted for NIOSH by the USDA-NASS. Changes in ROPS prevalence rates at the state level between the two time periods were assessed using a two-sample paired t-test with unequal sample sizes. Poisson regression was used to assess the association between ROPS prevalence rates and tractor overturn fatality rates at the state level. Overall, 49 of the 50 states had an observed increase in the percentage of farm tractors equipped with ROPS from 1993-1995 to 2001 and 2004. This increase was statistically significant for 34 states. Large shifts in ROPS prevalence were found within individual states and in clusters of states. These include a major increase in the southeastern U.S. and some western states. However, a core of states in the northeast (many of them in or near the Appalachian Mountains) through the upper midwest remain in the bottom quartile for ROPS prevalence. For the years 1992 through 2004, the highest fatality rates were observed in many of the same states that were identified previously as having persistently low ROPS prevalence rates. There is a clear relationship between low state-level ROPS prevalence rates and high state-specific tractor overturn fatality rates. While progress has been made in increasing the percentage of ROPS-equipped farm tractors, it is projected that ROPS prevalence rates will not reach a protective level nationally until after 2015. Regionally, the northeast and midwest will not reach protective levels of ROPS-equipped tractors until after 2020. Based on the adoption rates observed, tractor overturn rates will likely continue to be a more localized, but significant, public health issue for several states beyond the year 2020. The results of this study show the geographic areas of the U.S. where the greatest need exists, and where a greater emphasis should be placed on ROPS promotion activities. However, addressing this public health issue on a large scale will require resources and an organized commitment, which have historically been lacking.     

安全驾驶室翻车保护结构的有限元分析

车辆驾驶室在翻车时受到巨大的冲击载荷,其翻车保护结构应具有足够的侧向刚度来阻止其变形,同时又要能够吸收一定的能量.以某矿用自卸车翻车保护结构为例,采用弹塑性理论和有限元非线性分析方法,建立了翻车保护结构的非线性有限元模型,对模型进行侧向、竖向和纵向载荷的逐次加载分析,结果表明:翻车保护结构上横梁的端点已进入塑性变形状态,能量吸收达到国际标准规定的要求,翻车保护结构的构件未侵入变形限制量(DLV).     

Characteristics of an ozone deposition module II: Sensitivity analysis

An ozone deposition module is currently being developed which will allow the estimation of stomatal fluxes of ozone into a number of vegetation types. This model is designed to be linked into a regional chemical-transport model for use within the European Monitoring and Evaluation Programme (EMEP), to provide information on possible risks to vegetation across Europe. This paper investigates the sensitivity of this model to some of the important input parameters, for two land-cover classes (temperate coniferous forests, temperate cereals). Of the factors contributing to the stomatal conductance considered within this study, those controlling soil moisture seem to be the biggest source of uncertainty. As ozone damage is believed to be driven by flux into the leaf rather than by ambient concentrations, this study suggests that flux modelling may be a practical alternative to the use of the AOT40 concept which is currently used to guide assessments of vegetation risk.     

基于横向力系数的汽车急转防侧翻车速计算模型与仿真

针对汽车转向行驶时常因车速过快而引发侧翻事故这一问题,通过建立车辆转向行驶的力学模型,分别对刚性车体和考虑悬架作用车体在急转工况下的受力状况进行分析;在分析车辆转向时横向载荷转移、悬架运动等因素对横向力系数影响的基础上,将横向力系数的计算方法进行改进;根据横向力系数与车速间的关系,建立了基于横向力系数的汽车急转工况防侧翻临界安全车速计算模型;选用某型商用车结构参数为例,通过Matlab软件仿真的方法将所建立模型与其他4种弯道安全车速计算模型进行对比分析,该模型所得临界安全车速处于其他4种车速模型所得结果的区间内;同时,采用车辆动力学软件Truck Sim进行不同转弯半径下的车辆转向侧翻仿真对该模型进行验证,模型所得安全车速值比Truck Sim软件仿真所得侧翻临界车速值约小10%。该研究为急转工况下车辆的侧翻评价以及车辆转向行驶的主动安全控制提供了参考。     

The ecological effectiveness of protected areas: The United Kingdom

Given the importance placed on protected areas, determining their effectiveness in representing and maintaining biodiversity is a core issue in conservation biology. Nonetheless, frameworks identifying the breadth of issues associated with this effectiveness, and case studies of how well these are understood in particular regions, remain lacking. In this paper, we provide such a framework and an overview of the current state of knowledge of the ecological effectiveness of protected areas in the United Kingdom. Arguably, better data are available to address such issues in this region than anywhere else in the world. Nonetheless, studies remain scarce and have focussed foremost on the, rather narrow, issue of the effectiveness of management actions on individual sites in order to deliver fixed conservation objectives and discharge statutory responsibilities. Some attention has also been paid to how well the regional collection or portfolio of protected areas performs, particularly in capturing biodiversity features. Work on the extent to which protected areas in the United Kingdom form effective functional networks is in its infancy, but initiatives are under development. We identify some of the questions about the effectiveness of protected areas to which answers need to be known at the site, portfolio and network levels, and how significant progress might be achieved in addressing these.     

Decision analysis to guide recovery of the po‘ouli, a critically endangered Hawaiian honeycreeper

We used a probabilistic decision tree to help select among alternative recovery strategies for the Po‘ouli, a critically endangered forest bird endemic to the Hawaiian island of Maui. The Po‘ouli is one of the rarest birds in the world, with only three individuals known, and no breeding pairs. The most urgent conservation need for the species is to create a breeding pair and obtain eggs for captive propagation. Seven recovery strategies had been proposed, and there was disagreement among conservation workers about which strategy to pursue. In addition to lengthy discussions, a decision tree was introduced to provide an objective way of quantifying the chance of success under each alternative. All available information was used to attempt evaluation of each node in the decision tree. The overall chance of obtaining eggs was calculated by multiplying estimates at each node under each alternative. All options produced low estimates of potential success, but two options, removal of all birds to captivity and placement of the birds in a field aviary in an accessible location, produced similar estimates of success. The US Fish and Wildlife Service and the Hawaii Division of Forestry and Wildlife eventually agreed that removal to captivity was the preferred alternative because it could be implemented quickly, which was important considering the advanced age of the birds, and would make it easier to provide veterinary care and ensure their safety from predators, severe weather, and vandals. Decision trees and other structured models should not be relied on exclusively, but they can provide an objective method of helping to make difficult conservation decisions and provide a record of complex thought processes used in reaching a determination. The case of the Po‘ouli may serve as a template for navigation towards a decision to recover other species of extreme rarity.     

基于数据包络分析和人工神经网络的变量施肥决策方法研究

采用数据包络分析(DEA)方法评价玉米施肥单元的投入产出技术效率，把非DEA有效的单元进行投影，使之DEA有效，所获得的投影数据供神经网络训练使用。建立3层BP神经网络模型，以土壤养分和产量为输入，以施肥量为输出，并结合输入输出的价格因素扩展模型，实现利润最大化决策。该模型既为充分使用所有试验数据引入了可行方法，又弥补了传统施肥决策方法中非线性关系描述的不足。应用表明，该模型可以揭示施肥单元的需肥特性和提供最佳施肥方案，目标产量不超过9750 kg/hm²时，预测结果较合理。