We walked a research route of six kilometers through three Belgian cities: Antwerp, Brussels, and Namur. The results were the same everywhere: 4 to 5 times as many cans and bottles on the streets as in the Netherlands (where a deposit system has been introduced).
In all cities, we picked up around 200 to 250 drink containers from the streets over those six kilometers. This was despite walking through and around the city centers, where cleaning efforts are generally higher—meaning they are usually cleaner than the surrounding neighborhoods.