Indeed this solution has been standard in much of Europe for decades. It seems to have had slower uptake in the US. Donald Norman’s ”The Design of Everyday Thi

Indeed this solution has been standard in much of Europe for decades. It seems to have had slower uptake in the US. Donald Norman’s ”The Design of Everyday Things”, 2013 edition, contains this passage in a list of different faucet designs (p. 151): > Control temperature and rate of flow. Use two separate controls, one for water temperature, the other for flow rate. (I have never encountered this solution.) I e-mailed Don about it a few years ago, and by then he had encountered it.