That's a fantastic and practical question. Getting bin spacing right is a delicate balance between keeping the trail clean and not disrupting the natural experience. Based on common practices from park management and Leave No Trace principles, here’s a natural approach.
First, consider the trail's profile. High-traffic areas like trailheads, scenic overlooks, and junctions are prime locations. Everyone congregates there, making a bin convenient and preventing litter piles. For the main trail, spacing depends heavily on usage intensity. A heavily used 2-mile loop near a city might need bins every half-mile, while a remote 10-mile wilderness trail might only have them at the termini.
The golden rule is: the more remote and natural the area, the fewer bins you should install. Why? Bins can attract wildlife, create odors, and become eyesores if not serviced frequently. In many backcountry areas, the best practice is a "pack it in, pack it out" policy with no bins at all, educating hikers to carry their own trash out.
A key factor is maintenance capacity. A bin is a promise. If you place one, you must commit to regular, reliable emptying. An overflowing bin is worse than none at all, as it creates a concentrated litter problem. Your spacing must align with your crew's ability to service them, especially in peak season.
Finally, integrate clear signage. At each bin, a friendly reminder like "Help keep our trail wild" reinforces the message. At the trailhead, inform hikers of bin locations and the pack-in/pack-out expectation.
In short, cluster bins at key infrastructure points, space them based on traffic and remoteness, and never install more than you can reliably maintain. The goal is to support cleanliness while encouraging personal responsibility for our shared natural spaces.