So, what exactly is so wrong about the current use of pickup trucks? I mean, after all, can't you just get everything from the back?
The problem is that speed is often a key factor in how trucks are used. Workers may disregard their own safety and the long-term consequences of improper use in order to get the job done faster. Even rear access is quite hard to do properly, but I'm going to focus on side access.
If side access were practical and quick, it would offer a huge time savings by allowing more crew members to access the bed safely at the same time. By increasing the speed of access, it offers a fighting chance at actually improving safety at the same time. The diagram below illustrates body positions while lifting, based on the K'nex prototype from the last post. The three rows show lifting with no aid, lifting with a low-height step, and lifting with a higher access step, and are modeled on the typical OMNRF ranger's 60-pound hose pack (pictured in orange.)
So what's the problem then? In order to analyze the ergonomics of these scenarios, I'll turn to the (UK) Health and Safety Executive, who has published an excellent and comprehensive guide to manual lifting safety. Two figures from the HSE guide illustrate two key problems.
Figure 23 shows how increased extension of the arms reduces an individual's capacity. When fully extended, it can drop as low as 20%. Notice how the figure lifting the hose pack in the top row (who has no aid) has his/her arms fully extended through the entire lift- this is very unsafe, and would likely cause stress and/or strain.
Figure 15 shows ideal weight lifting limits based on the height of the load. The maximum recommended weight in any circumstance is 25 kg, approximately that of the hose pack routinely and frequently lifted by OMNRF rangers. The only time that the HSE deems a lift this heavy to be safe is when the arms are at a right angle, and the load at elbow height.
Note that the only lifting position from the side of the truck that comes close to meeting the 100% capacity threshold in Figure 23, and the maximum allowed weight in Figure 15 is the high access step. In a later post, I'll examine the safety of standard lifting procedures from the back of the truck, and from within the bed enclosure, as typically performed by numerous types of professionals.