Roads and building footprints are a starting point. Procedural generation gives roads width and turns footprints into three-dimensional buildings. The plan is to use defaults for details the map may leave out, such as floor counts.
A building can look fine and still be unreachable. Pickup and drop-off candidates should sit on connected parts of the road network. The first pass will use a small area to find disconnected roads and unreachable destinations, then rerun the same inputs as the generation rules improve.