Who cares how much relative space the roads take up?
I agree, you personally will experience better air in the suburbs. Everyone in aggregate will experience worse air due to your drive between the city and suburbs.
That's a variable that affects travel time (because even moreso less stuff within a given radius).
The most bizarre thing about the Narrow Streets proposal is, how they hell are bikes or buses supposed to work at reasonable speed if the streets are choked with them (and pedestrians, who would apparently have right of way on the same paths as bikes and buses, rather than parallel sidewalks).
The general response is "it creates problems" -- traffic, congestion, auto-centric neighbourhoods (which are poor places for children, the elderly, the disabled), and pollution.
I find more compelling the case laid out in the StrongTowns blog, by Charles Marohn, over several articles, that sprawl 1) costs more in the long term and 2) ultimately creates an unsustainable expenses-to-revenues balance.
Suburbs developed with cars, when cheap gasoline and asphalt made distance, rather than height (as in New York City) cheap. Homes were dropped on quarter-acre lots, retail centralised, and (in the US model) land use generally restricted to single-use: a lot is either commercial or residential, and industrial uses are kept widely separated.
Before that, cities were dense, because virtually all movement was on foot, by hand-cart, or, if you were wealthy, by a horse-drawn cart or carriage. Cities were also limited in size, because everything that went in had to come out, and that also generally happened by one or more of the above means -- no electrical sewerage pumping substations. Cholera and typhoid were killing tens of thousands of people per year in mid-19th century New York and London.
Space means you need more of everything: power lines, water mains, sewer lines, gas, cable, internet, streets, ... And maintenance for all of the above. At the same time, densities are too low to support intensive use -- think factory or even office jobs, or dense retail. Reliance instead is on moving people to retail centres -- built at a remove from either housing or city centres.
If you've got the resources (and cheap fuel), the spread-out life is ... relatively pleasant. If you cannot afford a car, or have had your licence revoked (drink driving, tickets, in some cases a penalty for failure to pay child support, or miscellaneous infractions), or can no longer drive (blind, disabled, epilepsy, ...), not so much. Transit options are almost always poor, and options such as walking or cycling not well supported.
https://www.strongtowns.org/journal/2017/1/9/the-real-reason...
Fully pricing in deferred future costs might help.
Is there even ONE city in the US that does it this way?
Can't we talk San Francisco into trying this approach? What are the objections?