[1] https://upload.wikimedia.org/wikipedia/commons/thumb/8/85/Ya...
[1] https://upload.wikimedia.org/wikipedia/commons/thumb/8/85/Ya...
They could also use bicycle lanes, but cyclists won't like it.
But you can't make things obscenely large in the beginning since then if the area doesn't take off you have a huge amount of infrastructure that still needs maintenance and it also feels like a ghost town with less usage.
It was all a lot easier in the 20th century because there wasn't this mix of speed/capability. The cars were shit, horse carriages aren't exactly fast, bicycles were shit... You had | 20hp trabantesque cars - 5hp horse carriage - bicycle - pedestrian |. Now you have | 400 hp cars - faster (e)bicycles - pedestrians | combined with increased safety culture so you need more splittage and more barriers (be it trees, an actual barrier, curvy roads built to slow people down, etc)
Maybe they won't ever become a "big thing", but Zipline is already delivering food directly to consumers in TX and elsewhere.