http://www.conveyor-center.com/hytrol/gates.htm
Here is a site that shows typical gates. All personal working in this area (the 2nd and 3rd level of a mezzanine picking module) would be familiar with the gates. Most likely using them tens of times a day to perform their daily tasks.
I am designing a picking module for a warehouse where I had hoped to use lift gates throughout the layout to act as egress points for personal. The village (located in Illinois) has dictated the max distance to exits, which would be met, but is uncertain if having to walk through the lift gates...