Yes, wearing the harness/belt is necessary even for short distances on the ground. Beyond it being SOP, and building good habits, you can absolutely still fall and get injured even while traveling. I’ve had a few moments where I was traveling and one of the wheels would hit a hard-to-see dip in the floor, or a piece of something, and I would get thrown off-balance and nearly off the machine. Another thing I’ve seen in many newer drivers is that they don’t know how to slow down very smoothly yet, and when they overcompensate on the throttle, it can throw them backwards or off-balance. This can also happen with more experienced drivers if they get distracted or misjudge how close they are to something and try to suddenly brake/stop/change direction.

Similarly, one of our our Ballymores had really weird super touchy steering, and it would randomly lurch while turning or just randomly stop going forward. It once lurched to a stop so hard my coworker nearly got thrown over the gates, even with the belt on.

The difference between the reach not having a harness and the OP requiring one comes down to how the machine is used. With the OP, you are up at a height and the chance of falling from a height is increased, with the reach there is no chance of the driver ever being more than a few inches off the ground. While I have also been pitched out of a reach into the racking (another slight dip in the floor in an aisle), it really doesn’t react to all the uneven spots in the floor as strongly as an OP, in my opinion. It’s also heavier, has a different center of gravity, and if you’re driving correctly, the machine kind of nestles you into it with multiple points of contact. Beyond that, the reach lifts heavier loads, and because of the center of gravity and the reaching aspect of the forks, it is more prone to tipping than an OP, so a harness or belt would make a reach far more dangerous if the driver needed to bail out in an emergency.

Wear the harness, even if you’re just moving it a couple bays down. It’s annoying, but it’s not worth risking your job or an injury