Ever noticed that public seating in subways, well, kind of sucks? Chalk those uncomfortable benches up to a carefully considered design plan, Vox explains in the video below.

Every single detail—from the stiff material to the awkwardly positioned arm rests—is intentional, and intended to help commuters rest their legs while not getting too comfortable. That way, they'll hop on the next train instead of loitering (or even taking a nap) on a public perch.

The underlying concept behind these design decisions goes by several names, including defensive design. Defensive design is intended to regulate public behavior, and to prevent everything from unwanted skateboarders to birds from encroaching upon an urban space. Examples include sprinklers under building awnings, turned on to keep homeless slumberers at bay, or security cameras in subway turnstiles.

Defensive design has been shown to reduce crime, vandalism, and loitering. But while effective, the philosophy has its critics, who claim that it doesn't always accommodate those with disabilities or social disadvantages, and it may not always be particularly humane.

Learn more about the pros and cons of defensive design by watching the video below.