That's a great observation! You're right, a lot of public trash bins, especially the classic metal ones, are round. It's one of those subtle design choices in cities that we often overlook. There isn't one single reason, but rather a combination of practical, economic, and even psychological factors.
First, think about safety. A round bin has no sharp corners. In a crowded sidewalk or park, this minimizes the risk of people, especially children, bumping into it and getting hurt. It's a simple but important consideration for public furniture.
Durability and manufacturing also play a big role. Cylindrical shapes are structurally strong and resist dents better than flat panels. They are also easier and often cheaper to manufacture through processes like metal spinning, requiring fewer welded seams than a square box. This means they last longer with less maintenance.
From a user's perspective, the 360-degree access is key. You can approach and toss your trash from any angle without having to "find the front." This is incredibly convenient in busy areas. For the collection crews, round bins are often lighter and easier to lift and maneuver when empty, and they roll smoothly when tipped onto their side.
There's also a "cleanliness" aspect. Square bins have internal corners where garbage can get stuck and compact, making them harder to empty and clean thoroughly. A smooth, curved interior allows waste to slide out more easily.
Finally, we can't ignore aesthetics. The round shape is often seen as more friendly, soft, and organic, blending slightly better into public spaces than hard-edged boxes. It's a small touch that contributes to the overall feel of an area.
So, while you'll certainly find square and rectangular bins too (often for specific spaces or higher capacity), the humble round bin has earned its place through a clever mix of safety, economy, durability, and user-friendly design. It's a small circle of smart urban planning!