Good essay by Matt Blaze:
Somehow, for all the attention to minutiae in the guidelines, everything ends up just slightly wrong by the time it gets put together at an airport. Even if we accept some form of passenger screening as a necessary evil these days, today's checkpoints seem like case studies in basic usability failure designed to inflict maximum frustration on everyone involved. The tables aren't quite at the right height to smoothly enter the X-ray machines, bins slide off the edges of tables, there's never enough space or seating for putting shoes back on as you leave the screening area, basic instructions have to be yelled across crowded hallways. According to the TSA's manual, there are four models of standard approved X-ray machines, from two different manufacturers. All four have sightly different heights, and all are different from the heights of the standard approved tables. Do the people setting this stuff up ever actually fly? And if they can't even get something as simple as the furniture right, how confident should we be in the less visible but more critical parts of the system that we don't see every time we fly?