* "Most areas with heavy pedestrian traffic have sidewalks." I am uncertain on this one, as heavy pedestrian traffic is more frequent on mixed-use streets. Sidewalks are only used in places with car-centric design, which discourages walking.
* "Even with cars taking up much more space, a bunch of cars traveling at 25 mph are able to carry a many more people through a distance X in a period of time T than the equivalent walking would be able to." I am uncertain on this, because cars require very large amounts of space both for the physical size of the car, the spacing between cars, and the spacing between groups of cars at an intersection.
* "It'd be incredibly eco-unfriendly, expensive, and impractical to have two different types of roads" I'd be interested in a source for this, as I've generally heard that separating out usage improves the efficiency of each. Cars go faster because there are fewer stops requires. Pedestrians die less often because there are fewer cars nearby.
* "Bike lanes are less common than sidewalks" This is correct by my experience, but I've only lived in places with car-centric city planning. Can you provide a source?
I'm interested in continuing this conversation, but not if it is a conversation between sourced comments and unsourced assertions.
As for the later, why is that any better than just sidewalks and crosswalks, which the majority of areas with heavy pedestrian traffic already have? It'd be incredibly eco-unfriendly, expensive, and impractical to have two different types of roads for cars and pedestrians when we already have a solution that works just fine - sidewalks.