Posted By Gordon Thelwell
Hi TBC,
I am not aware of specific standards for your needs but would consider it good practice to emulate similar mobile industria vehicular standards, perhaps HGV.
Failing that, i recently put together a little article regarding the visual aspects of operating a FLT - Pallet Racking interface within a warehouse environment. I hope it mat contribute to your final assessment:
We have surprisingly low visual acuity (resolution) in parts of the visual field that are not at the center of where we are looking — the center of gaze. We are not aware of this because we usually move our center of gaze to whatever we want to look at.
The center of gaze, called the "fovea," has a higher density of cones than anywhere else on the retina. In fact, there are no rods at all. The fovea evolved to have the highest possible visual acuity, and the cones are as small as they can possibly be, and still be alive. Moreover, in the fovea, the retinal ganglion cells have smaller receptive fields, and in the periphery, they have much larger receptive fields.
The fact that our vision has the highest acuity in the center of gaze does not mean that vision in the rest of the visual field is inferior — it’s just used for different things. Foveal vision is used for scrutinizing highly detailed objects, whereas peripheral vision is used for organizing the spatial scene, and for seeing large objects. Our foveal vision is optimized for fine details, and our peripheral vision is optimized for coarser information.
You can demonstrate this effect more simply by focusing on one of the words on this page while at the same time trying to make out other words to the right or left. You may be able to make out a word or two, depending on how far the page is from your eyes. But the area that you can see clearly is the area imaged on the fovea of your eye.
The visual characteristics of Pallet Racking play an important role in affecting when and if the Fork Truck Operator is able to detect The Pallet Rack. Contrast of the Racking with the background is one of the primary characteristics affecting its detectability. Increasing both the color contrast and brightness contrast between the racking and the background will increase the ability of the operator to detect the rack.
Pallet Racking is often painted dark colors (e.g., grey, brown, navy blue) to make dirt less noticeable. This makes the racking difficult to detect, particularly against a dark background. Contrasting Rack Armour Colors increase the visibility of the racking against both dark and light backgrounds, while the use of reflective (and photo luminescent ) material, if properly illuminated, can also provide improved attention-getting properties.
Detection of the racking is more difficult at night or warehouse compartment (e.g. freezers or chillers) when artificial light is solely relied upon as a light source. Additional alerting devices mounted on the exterior of the rack, can enhance its conspicuity by providing greater contrast with the background environment.
Conspicuity is the property of an object that enables it to be noticed. Although dominated by vision, operating MHE is a highly cognitive task. It usually occurs in a visually cluttered environment, requires the simultaneous use of central and peripheral vision and involves relatively complex MHE-control activities. Whilst functional differences between the central and peripheral visual fields are well documented, the linkage between the two is less understood.
In a typical test of the visual field, the operator fixates on the point where the raised palletized load is situated. Thus, a standard visual test cannot predict how efficiently an operator can use peripheral visual information in complex tasks such as operating MHE. It has been shown that peripheral retinal sensitivity may be impeded as the amount of information the subject is required to process mentally is increased.
This visual field “narrowing” may be applied to the warehouse environment, in that an operator’s attention is usually divided between the relevant features of the warehouse environment and other tasks, such as the simultaneous controlling of speed and direction of the MHE and its load, navigating with aisle signs and using in-MHE information systems. As a consequence, important visual stimuli in the periphery may remain undetected when cognitively demanding tasks involving central vision are being performed. Thus, the proximity of the MHE to the vulnerable lower sections of an upright section is difficult to monitor in a manner that is reasonably practicable and the risk of impact damage occurring increases.