I think ground level in city centers should be for pedestrians and less-than-15mph bikes (and other slow vehicles 120kg or less). Everything else is either elev

I think ground level in city centers should be for pedestrians and less-than-15mph bikes (and other slow vehicles 120kg or less). Everything else is either elevated or subterranean, including bike lanes and most definitely cars and trucks. Conveyance is a utility like sewer or electricity, and like sewer and electricity, it shouldn’t be flowing at ground level. Minneapolis has some interesting solutions. The skyway (in both Minneapolis and St. Paul) connects all the buildings in the downtown via elevated (or subterranean) pedestrian pathways, important in the 0 degrees F (-18C) winter. But ideally, you’d flip the situation with the cars and trucks on the non-ground-level with the streets purely for people or low speed and low mass vehicles like bikes. Minneapolis also has the Greenway, superhighway for bikes that is grade-separated from much of the rest of the city (sitting below, in like a greenery-surrounded canyon, with bridges above), an old railroad route. Pretty fantastic.