Sounds Jim Dandy to me as I am sure your 15 minute cities are going to be economically segregated. Mine will have restaurants, cinemas, parks, and upscale living with river views. Yours will be a food dessert with an oil refinery on one side, a landfill on the other and an airport on the third.. Of course you will be allowed to ride your bike over to my 15 minute city to scrub my toilet and wash my windows. I of course will from time to time take a seat, drop the window shade and ride the train, first class car of course, over to that airport to catch a plane to the Costa del Sol.