John R. Powers

Preventing tractor rollover fatalities: performance of the NIOSH autoROPS.

Approximately 132 agricultural tractor overturn fatalities occur per year. The use of rollover protective structures (ROPS), along with seat belts, is the best known method for preventing these fatalities. One impediment to ROPS use, however, is low clearance situations, such as orchards and animal confinement buildings. To address the need for ROPS that are easily adapted to low clearance situations, the Division of Safety Research, National Institute for Occupational Safety and Health (NIOSH), developed an automatically deploying, telescoping ROPS (AutoROPS). The NIOSH AutoROPS consists of two subsystems. The first is a retractable ROPS that is normally latched in its lowered position for day-to-day use. The second subsystem is a sensor that monitors the operating angle of the tractor. If a rollover condition is detected by the sensor, the retracted ROPS will deploy and lock in the full upright position before ground contact. Static load testing and field upset tests of the NIOSH AutoROPS have been conducted in accordance with SAE standard J2194. Additionally, timed trials of the AutoROPS deployment mechanism were completed. The design of the retractable ROPS and sensor, as well as the results of the different testing phases are discussed.

Performance of an automatically deployable ROPS on ASAE tests

In the U.S., approximately 132 agricultural tractor overturn fatalities occur per year. The use of rollover protective structures (ROPS), along with seat belts, is the best-known method for preventing these fatalities. However, one impediment to ROPS use is low-clearance situations, such as orchards and animal confinement buildings. To address the need for ROPS that are easily adapted to low-clearance situations, the Division of Safety Research, National Institute for Occupational Safety and Health, developed a prototype automatically deploying, telescoping ROPS (AutoROPS). The NIOSH AutoROPS consists of two subsystems. The first is a retractable ROPS that is normally latched in its lowered position for day-to-day use. The second subsystem is a sensor that monitors the operating angle of the tractor. If an overturn condition is detected by the sensor, the retracted ROPS will deploy and lock in the full upright position before ground contact. Static load testing and field upset tests of the NIOSH AutoROPS have been conducted in accordance with SAE standard J2194. Additionally, timed trials of the AutoROPS deployment mechanism were completed. The results of these tests show that the NIOSH AutoROPS has significant potential to overcome the limitations of current ROPS designs for use in low clearance as well as unrestricted clearance operations.

Factors Affecting Extension Ladder Angular Positioning

Objective: The study objectives were to identify factors affecting extension ladders’ angular positioning and evaluate the effectiveness of two anthropometric positioning methods. Background: A leading cause for extension ladder fall incidents is a slide-out event, usually related to suboptimal ladder inclination. An improved ladder positioning method or procedure could reduce the risk of ladder stability failure and the related fall injury. Method: Participants in the study were 20 experienced and 20 inexperienced ladder users. A series of ladder positioning tests was performed in a laboratory environment with 4.88-m (16-ft) and 7.32-m (24-ft) ladders in extended and retracted positions. The setup methods included a no-instruction condition and two anthropometric approaches: the American National Standards Institute A14 and “fireman” methods. Performance measures included positioning angle and time. Results: The results indicated that ladder setup method and ladder effective length, defined by size and extended state, affected ladder positioning angle. On average, both anthropometric methods were effective in improving extension ladder positioning; however, they required 50% more time than did the no-instruction condition and had a 9.5% probability of setting the ladder at a less-than-70° angle. Shorter ladders were consistently positioned at shallower angles. Conclusion: Anthropometric methods may lead to safer ladder positioning than does no instruction when accurately and correctly performed. Workers tended to underperform as compared with their theoretical anthropometric estimates. Specific training or use of an assistive device may be needed to improve ladder users’ performance. Application: The results provide practical insights for employers and workers to correctly set up extension ladders.

Research to improve extension ladder angular positioning

A leading cause for extension ladder fall incidents is a slide-out event usually related to suboptimal ladder inclination. An improved ladder positioning method or procedure could reduce the risk of ladder stability failure and the related fall injury. The objective of the study was to comparatively evaluate the effectiveness of a multimodal angle indicator with other existing methods for extension ladder angular positioning. Twenty experienced and 20 inexperienced ladder users participated in the study. Four ladder positioning methods were tested in a controlled laboratory environment with 4.88 m (16 ft) and 7.32 m (24 ft) ladders in extended and retracted positions. The positioning methods included a no-instruction method, the current standard anthropometric method, and two instrumental methods - a bubble level indicator, and a multimodal indicator providing direct feedback with visual and sound signals. Performance measures included positioning angle and time. The results indicated that the anthropometric method was effective in improving the extension ladder positioning angle (p < 0.001); however, it was associated with considerable variability and required 50% more time than no-instruction. The bubble level indicator was an accurate positioning method (with very low variability), but required more than double the time of the no-instruction method (p < 0.001). The multimodal indicator improved the ladder angle setting as compared to the no-instruction and anthropometry methods (p < 0.001) and required the least time for ladder positioning among the tested methods (p < 0.001). An indicator with direct multimodal feedback is a viable approach for quick and accurate ladder positioning. The main advantage of the new multimodal method is that it provides continuous feedback on the angle of the device and hence does not require repositioning of the ladder. Furthermore, this indicator can be a valuable tool for training ladder users to correctly apply the current ANSI A14 standard anthropometric method in ladder angular positioning. The multimodal indicator concept has been further developed to become a hand-held tool in the form of a smart phone application.

Effectiveness of a worker-worn electric-field sensor to detect power-line proximity and electrical-contact.

PROBLEM Construction workers suffer the most electrocutions among all industries. Currently, there are no electrical contact warning devices on the market to protect workers. This paper proposes a worker-worn electric-field sensor. As the worker is in proximity to, or in contact with, a live power-circuit, the sensor sets off an audible/visual warning alarm. The sensor also has the potential to wirelessly trip a wireless-capable circuit breaker, and to trigger a wireless transmitter to notify emergency response of an electrical contact. METHODS An experiment was conducted to measure electric-field variation on simulated human-wrists (10 defrosted hog-legs) in various proximities and in electrical-contact to a simulated power-circuit. The purpose of these tests was to determine the feasibility of developing a worker-worn electric-field detection sensor for use in protecting workers from contact with energized electrical conductors. RESULTS This study observed a significant electric-field-magnitude increase as a hog-leg approaches the live-circuit, and the distinct electric-field-magnitude jump as the leg contacts with the live-circuit. The observation indicates that this sensor can be an effective device to warn the workers of electrical hazards. Additionally, the sensor has the potential to wirelessly trip a wireless-capable circuit-breaker and trigger a wireless transmitter (such as a cell phone) to notify an emergency response. The prompt notification prevents the worker from further injury caused by postponed medical-care. IMPACT ON INDUSTRY Widespread use of this sensor could lower electrocution and electrically related injury rates in the construction industry.

A new video-synchronized multichannel biomedical data acquisition system

This data acquisition system records video frames onto a video tape, and simultaneously acquires biomedical data along with video time codes onto a computer hard disk to achieve a 30-min video-synchronized data recording with a summed data rate of 2.16 Mbit/s. A time-code-bridge file created during acquisition matches each video frame-start with the corresponding index number of the acquired data. The mean synchronization accuracy of the system is 0.22 ms.

Estimation of the kinetic energy dissipation in fall-arrest system and manikin during fall impact

Fall-arrest systems (FASs) have been widely applied to provide a safe stop during fall incidents for occupational activities. The mechanical interaction and kinetic energy exchange between the human body and the fall-arrest system during fall impact is one of the most important factors in FAS ergonomic design. In the current study, we developed a systematic approach to evaluate the energy dissipated in the energy absorbing lanyard (EAL) and in the harness/manikin during fall impact. The kinematics of the manikin and EAL during the impact were derived using the arrest-force time histories that were measured experimentally. We applied the proposed method to analyse the experimental data of drop tests at heights of 1.83 and 3.35 m. Our preliminary results indicate that approximately 84–92% of the kinetic energy is dissipated in the EAL system and the remainder is dissipated in the harness/manikin during fall impact. The proposed approach would be useful for the ergonomic design and performance evaluation of an FAS. Statement of Relevance: Mechanical interaction, especially kinetic energy exchange, between the human body and the fall-arrest system during fall impact is one of the most important factors in the ergonomic design of a fall-arrest system. In the current study, we propose an approach to quantify the kinetic energy dissipated in the energy absorbing lanyard and in the harness/body system during fall impact.

Assessment of Fall-Arrest Systems for Scissor Lift Operators Computer Modeling and Manikin Drop Testing

Objective: The current study is intended to evaluate the stability of a scissor lift and the performance of various fall-arrest harnesses/lanyards during drop/fall-arrest conditions and to quantify the dynamic loading to the head/neck caused by fall-arrest forces. Background: No data exist that establish the efficacy of fall-arrest systems for use on scissor lifts or the injury potential from the fall incidents using a fall-arrest system. Method: The authors developed a multibody dynamic model of the scissor lift and a human lift operator model using ADAMS™ and LifeMOD™ Bio-mechanics Human Modeler. They evaluated lift stability for four fall-arrest system products and quantified biomechanical impacts on operators during drop/fall arrest, using manikin drop tests. Test conditions were constrained to flat surfaces to isolate the effect of manikin-lanyard interaction. Results: The fully extended scissor lift maintained structural and dynamic stability for all manikin drop test conditions. The maximum arrest forces from the harnesses/lanyards were all within the limits of ANSI Z359.1. The dynamic loading in the lower neck during the fall impact reached a level that is typically observed in automobile crash tests, indicating a potential injury risk for vulnerable participants. Conclusion: Fall-arrest systems may function as an effective mechanism for fall injury protection for operators of scissor lifts. However, operators may be subjected to significant biomechanical loadings on the lower neck during fall impact. Application: Results suggest that scissor lifts retain stability under test conditions approximating human falls from predefined distances but injury could occur to vulnerable body structures.

16-channel 500-Hz video-synchronized EMG data acquisition

A new video-synchronized 16-channel electromyography (EMG) data acquisition system was developed to increase the acquired signal frequency bandwidth. The system records human motion images onto a video tape, and simultaneously acquires EMG data along with the binary video time-code stream onto a computer hard drive. In realtime, the computer decodes the video time codes and creates a two-column time-code bridge file which matches the decoded video frame numbers with the corresponding index numbers of the acquired data at each of the video frame begins. With the bridge file, given a frame of recorded video on the TV monitor, the system is able automatically display a frame of the corresponding 16-channel data segment on the computer monitor, or vice versa. Currently, this system is capable of acquiring 30 minutes of 16-channel video-synchronized EMG data with a frequency bandwidth of 500 Hz per channel and a data resolution of 11-bits.

Evaluating the protective capacity of two-post ROPS for a seat-belted occupant during a farm tractor overturn.

This study evaluated the effectiveness of a commercial rollover protective structure (ROPS) and size-extended ROPS in protecting a 95th percentile male operator during tractor overturns. Six rear upset tests (commercial ROPS) and ten side upset tests (commercial and size-extended ROPS) were conducted. A 95th percentile instrumented male manikin was used in all tests. Head injury criterion (HIC15), 80 g limit on resultant head acceleration, neck injury criterion (Nij), and peak axial force (extension-compression) were employed to evaluate injury potential. In all rear tests, the manikins head impact with the ground was within the tolerance limits for head/neck injuries. Based on limited trials in the side tests, the study observed a small to moderate chance of neck injuries under the commercial and size-extended ROPS conditions; the injury risk was not statistically significant between these two test conditions. This study identified a risk of non-fatal injuries for large-size operators in side overturns, although the prevention effectiveness of commercial versus size-extended ROPS cannot be determined without further testing. These findings may have implications for future ROPS designs.