I have definitely noticed those waste bins with ash trays sitting on top, especially in busy outdoor areas like train stations, office courtyards, and smoking zones. And honestly, my answer to your question is: yes, they can be effective—but it depends heavily on design, placement, and maintenance.
From what I have observed in my daily life, these bins work best when the ash tray compartment is clearly visible and easy to use. For example, I remember walking through a park in London where each bin had a small, black, metal ashtray on top—just a shallow dish with a few holes. Smokers would naturally tap their cigarettes there without a second thought, and I saw fewer butts on the ground around those bins compared to ones without the ashtray feature. That suggests that making disposal convenient genuinely reduces litter.
However, effectiveness drops when the ash tray is too small or gets clogged with trash. I have seen models where people ended up stuffing cigarette packs or even coffee cups into the ashtray part, rendering it useless. Also, if the ashtray isn’t emptied regularly, smokers refuse to use a full tray and just toss butts elsewhere. In my experience, bins with removable, single-purpose ashtrays (rather than combined with the main waste compartment) tend to stay cleaner and get used more consistently.
Another factor I noticed is rain. In several cities, unshaded bins with ashtrays quickly fill with water, making them unappealing or even unusable. But when they are covered or have a drain design, smokers still use them.
So overall, I think they are effective as a small, practical fix—not a miracle cure. They help where people already have the intention to dispose properly, but they fail if not maintained. If I had to pick the best version, it would be those standalone “butt bins” (thin metal tubes attached to a pole), separate from regular waste bins. They feel purpose-built and tend to stay cleaner in my observations. But yes, the combined ones you described can work—as long as the ashtray is designed with care and kept empty.