Operator assessment of tractor roll angle with and without a tractor stability visual feedback device.

According to a 2004 National Institute for Occupational Safety and Health (NIOSH) report, approximately 250 to 350 fatalities occur each year due to incidents involving production agriculture workers and tractors. Tractor overturns account for about 150 to 200 of these deaths. The goals of this project were to study operators' understanding of tractor roll angles and test a device to effectively deliver stability information to the tractor operator. This project required the design and construction of a full-scale tractor cab roll simulator that was used to identify lateral roll angles at which volunteer participants felt uncomfortable, as well as lateral roll angles at which they would no longer operate a tractor. In addition, the participants performed a series of tasks to test the functionality of a visual slope indicator that was designed to help them estimate slope angles. The project tested 231 tractor operators' perceptions of safe operation on side slopes and 128 participants' interactions with the visual slope indicator. Testing showed that the visual slope indicator was able to influence the angle estimations of the novice tractor operator population and helped the entire population of participants more accurately rank the simulator scenarios.

National Safe Tractor and Machinery Operation Program: development and content evaluation.

Guidelines in the U.S. Department of Labor's Hazardous Occupations Order in Agriculture (AgHO) regulations state that youth can receive tractor safety certification after participating in a 10-hour course, or receive tractor and machinery safety certification after participating in a 20-hour course. An additional four hours of orientation to on-farm hazards and general safety is required to receive full certification in a 24-hour course. Previous research has shown that traditional safety education certification programs were conducted with non-standardized methods and old curriculum materials. The objective of the National Safe Tractor and Machinery Operation Program (NSTMOP) project was to design an effective, efficient, and accountable youth farm machinery certification program with national uniformity and a single set of economically producible instructional materials with demonstrated content validity. The format for the NSTMOP project was guided by focus groups, a national steering committee, and selected agricultural safety educators. Primary curriculum materials include a task sheet format, and new skills and driving evaluations. Data analysis indicates that the instructional materials, the instructional plan, and the evaluation of student participants satisfactorily met the objectives of the NSTMOP project and the AgHO regulations.

Motorist comprehension of the slow-moving vehicle (SMV) emblem.

While attaining widespread use and institutional acceptance in its 40 years on the road, crash data indicate that the slow-moving vehicle (SMV) emblem may not be meeting the safety needs of either the motoring public or SMV operators. This article addresses the possibility that the reasons for this include its inconsistent day/night appearance, potential confusion with other roadway symbols, its uncontrolled misuse, and poor driver education. This study is also the first to systematically evaluate the SMV emblem's comprehensibility by the general motoring public. Over 100 male and female drivers from 18 to 84 years of age gave open-ended responses to the presentation of a scale model SMV emblem displayed in its daytime and nighttime appearance. While the older drivers understood the meaning of the emblem better than their younger counterparts, overall emblem comprehension was still under 30%.

Age differences in dynamic contrast thresholds.

Contrast thresholds for sinusoidal gratings of 1.5-18 cpd were measured in young (M = 24 years) and older adults (M = 69 years). Thresholds were determined for stationary gratings, and for gratings that traveled along a circular path at 5, 10, and 15 deg/sec. For static gratings, age differences in thresholds were greater for intermediate and higher spatial frequencies. Grating motion increased thresholds for all observers, but older adults exhibited threshold increases at lower target velocities than the young. Age differences in velocity effects were generally greater at intermediate and higher spatial frequencies. Results are discussed in relation to age changes in temporal resolution and smooth pursuit gain.

Age differences in estimating vehicle velocity.

Automobile accidents among older adults may be related to difficulties in judging the speed of other vehicles. To examine this possibility, 3 groups of observers in the young adult, middle-aged, and older adult age ranges were asked to estimate the velocity of an isolated automobile traveling at 15-50 mph (24-80 kph). Across all age groups, perceived and actual velocity were related by a power function with an exponent of 1.36. Age was significantly and positively correlated with intercepts, but negatively correlated with exponents; that is, older observers showed less sensitivity to changes in actual velocity. Results bear on the issues of ontogenetic changes in accident involvement and sensitivity to motion.

Bandwidth of the contrast sensitivity function as an index of spatial vision with application to refraction.

The contrast sensitivity function (CSF), although containing more information than traditional measures of acuity, has found difficulty gaining clinical acceptance. The hesitancy of clinicians to adopt the CSF stems, in part, from the fact that it is not as readily interpreted as is acuity. In order to facilitate such interpretation, five indices of spatial vision which are derivable from the CSF were examined in a sample of 287 persons aged 5 to 85 years. All indices were found to be both age-sensitive and strongly related to each other, but bandwidth of the CSF was chosen as a practical index for clinical settings. In a second study, acuity and CSF bandwidth were measured under 0 to +/- 1 D optical blur. It was found that the correction providing best acuity also maximized CSF bandwidth, and that bandwidth was more sensitive to optical blur than was acuity. Results support the assertion that CSF bandwidth is a readily interpreted index of spatial vision that can be measured efficiently within the context of clinical refraction.

Age differences in Vistech near contrast sensitivity.

Contrast sensitivity was measured at near using the Vistech 6000 Contrast Test System (VCTS) in 287 persons aged 4 to 87 years. Obtained data compared well with those previously reported for the Vistech charts. Results indicate an age-related loss in sensitivity to intermediate and higher spatial frequencies. This is consistent with the age trends observed using other methods for measuring contrast sensitivity functions (CSFs). However, the Vistech charts yield contrast sensitivity values which are lower than those obtained previously with the Nicolet system. These between-method differences are greatest at lower spatial frequencies, and are attributed to the small number of grating cycles in the Vistech charts. The data are used to develop provisional age norms for the Vistech charts which allow the assessment of an individual's performance relative to their age cohort. Recommendations for use and future development of the Vistech charts are also given.

The effects of target borders on dynamic visual acuity: practical and theoretical implications.

The effects of target borders on the ability of observers to resolve moving targets (Landolt Cs) under a range of conditions were examined. Contrary to reported findings with stationary targets, it was predicted that the presence of borders would improve acuity for slow-moving targets because (i) overall stimulus energy is kept relatively constant as target detail varies, and (ii) a low-spatial-frequency component is held constant as target detail varies. In an experiment in which a two-sided border (above and below the target) was used, the predicted beneficial effect of the border at slow speeds was obtained. The results are discussed in terms of practical implications for the assessment of dynamic visual acuity as well as the potential neural mechanisms underlying performance.