There have been numerous pilot studies, e.g. those listed on https://en.wikipedia.org/wiki/Universal_basic_income . The problem is that opponents of UBI invariably point out that as only some people received it, and only for a limited time, that it wasn't universal, or that it took place in in some other country, or decades ago, so it doesn't apply in their country, or today.
> Show me how much UBI saves police departments, social welfare services, the health-care system,etc.
Its purpose is to ensure that everyone has their basic financial needs met, not to provide those particular government services.