Introduction: The ISO 5006-1 is used to evaluate visibility on earth-moving machinery but has been criticized for a cumbersome field method. Field conditions are difficult to reproduce. Investigators may be required to evaluate a particular machine's line of sight profile to examine how it contributed to an accident. However, the standard relies on values such as operator size and positioning that accident investigators may not possess. Furthermore, practitioners in various settings face limitations related to lighting, time, and space.
Methods: A computer simulation version of the standard was completed on a small lift truck machine and a larger haul truck. Variations on obstruction, or masking, calculation methods were completed to highlight the variability within the ISO 5006-1 standard under controlled conditions. Additionally, the impact of operator anthropometrics and seat positioning on masking measurements were quantified.
Results: Generally, ISO 5006-1 calculated masking widths and those measured using a monocular view point underestimated masking sizes as compared to a gold standard binocular measurement. Binocular and monocular measurements of the percentage visibility on a horizontal plane showed little difference (<1%). Furthermore, variations in operator anthropometrics and seat positioning showed minimal changes in measures of visibility (<2%).
Conclusions: Depending on the accuracy required for a given application, variations in visibility measurements may be considered acceptable or unacceptable. The variation of 300 mm observed in one case between a binocular masking width and monocular width exceeds the acceptable masking width (300 mm) defined by the ISO. However, variations in seat positioning and anthropometrics showed much smaller differences.