That's a great question that city planners and public works departments consider carefully. Based on common municipal standards and urban design practices, the most popular size for a downtown outdoor trash can is typically in the 35 to 55-gallon (approximately 130 to 210-liter) capacity range.
You'll most often see these as sturdy, cylindrical containers around 3 to 4 feet tall. This size hits a practical sweet spot. It's large enough to hold a meaningful amount of waste from pedestrians and visitors throughout the day, reducing the frequency of costly collections. Yet, it's not so massive that it becomes an eyesore or obstructs the sidewalk. In high-traffic areas like transit stops or popular park corners, you might find even larger units, sometimes up to 65 gallons. Conversely, in more spaced-out placements, smaller 20-30 gallon bins might be used.
The choice isn't just about volume. The footprint and height are designed for easy access—allowing someone to discard a coffee cup or wrapper without hassle—while being resistant to tipping over. Many modern downtown bins are also part of integrated "street furniture" that includes recycling compartments of similar size, promoting cleaner and more sustainable urban spaces. Ultimately, the most popular size is the one that best balances sufficient capacity, aesthetic fit, maintenance cost, and public convenience for a specific street's needs.