That's an excellent and often overlooked question! In an urban setting, the "most secure" lock for a trash can isn't about keeping valuables safe, but about preventing specific problems: unauthorized access by people or animals, litter scattering, and costly vandalism. There's no one-size-fits-all answer, as the best choice balances security, cost, durability, and ease of use for sanitation workers.
For standard public litter bins, a heavy-duty keyed cam lock is often the top choice. It's simple, weather-resistant, and requires a unique key for access, deterring casual rummaging. A step up in convenience for crews is the combination cam lock, eliminating key management issues while maintaining good security.
When dealing with larger commercial bins or enclosures, heavy-duty padlocks (shackless or shrouded) or bolt locks are more appropriate. They are highly visible deterrents against theft of the entire bin or access to its contents.
The emerging frontier is smart locks. These can provide audit trails, time-based access permissions, and remote control, ideal for high-security areas or regulated waste streams. However, they are the most expensive option.
Ultimately, the most secure mechanism is the one that is consistently used and maintained. A simple, robust lock that sanitation crews can easily operate every day is far more effective than a complex system that gets bypassed for efficiency. For most cities, a high-quality, stainless steel keyed or combination cam lock strikes the perfect balance between deterring pests, vandals, and unauthorized dumping while ensuring smooth municipal operations.